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  • 1
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    Concerns about quadrupole ICP-MS lead isotopic data and interpretations in the environment and health fields (2018)
    MDPI AG
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in International Journal of Environmental Research and Public Health 15 (2018): 723, doi:10.3390/ijerph15040723.
    Description: There has been a massive increase in recent years of the use of lead (Pb) isotopes in attempts to better understand sources and pathways of Pb in the environment and in man or experimental animals. Unfortunately, there have been many cases where the quality of the isotopic data, especially that obtained by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS), are questionable, resulting in questionable identification of potential sources, which, in turn, impacts study interpretation and conclusions. We present several cases where the isotopic data have compromised interpretation because of the use of only the major isotopes 208Pb/206Pb and 207Pb/206Pb, or their graphing in other combinations. We also present some examples comparing high precision data from thermal ionization (TIMS) or multi-collector plasma mass spectrometry (MC-ICP-MS) to illustrate the deficiency in the Q-ICP-MS data. In addition, we present cases where Pb isotopic ratios measured on Q-ICP-MS are virtually impossible for terrestrial samples. We also evaluate the Pb isotopic data for rat studies, which had concluded that Pb isotopic fractionation occurs between different organs and suggest that this notion of biological fractionation of Pb as an explanation for isotopic differences is not valid. Overall, the brief review of these case studies shows that Q-ICP-MS as commonly practiced is not a suitable technique for precise and accurate Pb isotopic analysis in the environment and health fields
    Keywords: Lead isotopes ; ICP-MS ; TIMS ; MC-ICP-MS ; Environment ; Humans ; Rats ; Fractionation
    Repository Name: Woods Hole Open Access Server
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  • 2
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    Comparison of phenology estimated from reflectance-based indices and solar-induced chlorophyll fluorescence (SIF) observations in a temperate forest using GPP-based phenology as the standard (2018)
    MDPI AG
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Remote Sensing 10 (2018): 932, doi:10.3390/rs10060932.
    Description: We assessed the performance of reflectance-based vegetation indices and solar-induced chlorophyll fluorescence (SIF) datasets with various spatial and temporal resolutions in monitoring the Gross Primary Production (GPP)-based phenology in a temperate deciduous forest. The reflectance-based indices include the green chromatic coordinate (GCC), field measured and satellite remotely sensed Normalized Difference Vegetation Index (NDVI); and the SIF datasets include ground-based measurement and satellite-based products. We found that, if negative impacts due to coarse spatial and temporal resolutions are effectively reduced, all these data can serve as good indicators of phenological metrics for spring. However, the autumn phenological metrics derived from all reflectance-based datasets are later than the those derived from ground-based GPP estimates (flux sites). This is because the reflectance-based observations estimate phenology by tracking physiological properties including leaf area index (LAI) and leaf chlorophyll content (Chl), which does not reflect instantaneous changes in phenophase transitions, and thus the estimated fall phenological events may be later than GPP-based phenology. In contrast, we found that SIF has a good potential to track seasonal transition of photosynthetic activities in both spring and fall seasons. The advantage of SIF in estimating the GPP-based phenology lies in its inherent link to photosynthesis activities such that SIF can respond quickly to all factors regulating phenological events. Despite uncertainties in phenological metrics estimated from current spaceborne SIF observations due to their coarse spatial and temporal resolutions, dates in middle spring and autumn—the two most important metrics—can still be reasonably estimated from satellite SIF. Our study reveals that SIF provides a better way to monitor GPP-based phenological metrics.
    Description: This research was supported by U. S. Department of Energy Office of Biological and Environmental Research Grant DE-SC0006951, National Science Foundation Grants DBI 959333 and AGS-1005663, and the University of Chicago and the MBL Lillie Research Innovation Award to Jianwu Tang and China Scholarship Council No. 201506190095 to Z. Liu. Xiaoliang Lu was also supported by the open project grant (LBKF201701) of Key Laboratory of Land Surface Pattern and Simulation, Chinese Academy of Sciences.
    Keywords: Solar-induced chlorophyll fluorescence ; Reflectance ; Phenology ; Fall phenological events
    Repository Name: Woods Hole Open Access Server
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  • 3
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    Variability of bed drag on cohesive beds under wave action (2016)
    MDPI AG
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Water 8 (2016): 131, doi:10.3390/w8040131.
    Description: Drag force at the bed acting on water flow is a major control on water circulation and sediment transport. Bed drag has been thoroughly studied in sandy waters, but less so in muddy coastal waters. The variation of bed drag on a muddy shelf is investigated here using field observations of currents, waves, and sediment concentration collected during moderate wind and wave events. To estimate bottom shear stress and the bed drag coefficient, an indirect empirical method of logarithmic fitting to current velocity profiles (log-law), a bottom boundary layer model for combined wave-current flow, and a direct method that uses turbulent fluctuations of velocity are used. The overestimation by the log-law is significantly reduced by taking turbulence suppression due to sediment-induced stratification into account. The best agreement between the model and the direct estimates is obtained by using a hydraulic roughness of 10 m in the model. Direct estimate of bed drag on the muddy bed is found to have a decreasing trend with increasing current speed, and is estimated to be around 0.0025 in conditions where wave-induced flow is relatively weak. Bed drag shows an increase (up to fourfold) with increasing wave energy. These findings can be used to test the bed drag parameterizations in hydrodynamic and sediment transport models and the skills of these models in predicting flows in muddy environments.
    Description: This research was supported by the Office of Naval Research funding of contracts N00014-07-1-0448, N00014-07-1-0756.
    Keywords: Water waves ; Muddy waters ; Coastal waters ; Currents ; Bed drag ; Drag coefficient ; Bottom shear stress ; Bottom friction ; Mud ; Cohesive sediment
    Repository Name: Woods Hole Open Access Server
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  • 4
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    Model behavior and sensitivity in an application of the Cohesive Bed Component of the Community Sediment Transport Modeling System for the York River estuary, VA, USA (2014)
    MDPI AG
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Marine Science and Engineering 2 (2014): 413-436, doi:10.3390/jmse2020413.
    Description: The Community Sediment Transport Modeling System (CSTMS) cohesive bed sub-model that accounts for erosion, deposition, consolidation, and swelling was implemented in a three-dimensional domain to represent the York River estuary, Virginia. The objectives of this paper are to (1) describe the application of the three-dimensional hydrodynamic York Cohesive Bed Model, (2) compare calculations to observations, and (3) investigate sensitivities of the cohesive bed sub-model to user-defined parameters. Model results for summer 2007 showed good agreement with tidal-phase averaged estimates of sediment concentration, bed stress, and current velocity derived from Acoustic Doppler Velocimeter (ADV) field measurements. An important step in implementing the cohesive bed model was specification of both the initial and equilibrium critical shear stress profiles, in addition to choosing other parameters like the consolidation and swelling timescales. This model promises to be a useful tool for investigating the fundamental controls on bed erodibility and settling velocity in the York River, a classical muddy estuary, provided that appropriate data exists to inform the choice of model parameters.
    Description: Funding by the National Science Foundation (OCE-1061781 and OCE-0536572) supported Fall, Harris, Friedrichs, and Rinehimer.
    Keywords: Cohesive sediment ; Critical stress ; Sediment transport modeling ; Erodibility ; Settling velocity
    Repository Name: Woods Hole Open Access Server
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  • 5
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    Evaluating remotely sensed phenological metrics in a dynamic ecosystem model (2014)
    MDPI AG
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Remote Sensing 6 (2014): 4660-4686, doi:10.3390/rs6064660.
    Description: Vegetation phenology plays an important role in regulating processes of terrestrial ecosystems. Dynamic ecosystem models (DEMs) require representation of phenology to simulate the exchange of matter and energy between the land and atmosphere. Location-specific parameterization with phenological observations can potentially improve the performance of phenological models embedded in DEMs. As ground-based phenological observations are limited, phenology derived from remote sensing can be used as an alternative to parameterize phenological models. It is important to evaluate to what extent remotely sensed phenological metrics are capturing the phenology observed on the ground. We evaluated six methods based on two vegetation indices (VIs) (i.e., Normalized Difference Vegetation Index and Enhanced Vegetation Index) for retrieving the phenology of temperate forest in the Agro-IBIS model. First, we compared the remotely sensed phenological metrics with observations at Harvard Forest and found that most of the methods have large biases regardless of the VI used. Only two methods for the leaf onset and one method for the leaf offset showed a moderate performance. When remotely sensed phenological metrics were used to parameterize phenological models, the bias is maintained, and errors propagate to predictions of gross primary productivity and net ecosystem production. Our results show that Agro-IBIS has different sensitivities to leaf onset and offset in terms of carbon assimilation, suggesting it might be better to examine the respective impact of leaf onset and offset rather than the overall impact of the growing season length.
    Keywords: Phenology ; Remote sensing ; Dynamic ecosystem model ; Agro-IBIS ; MODIS
    Repository Name: Woods Hole Open Access Server
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  • 6
    Electronic Resource
    Electronic Resource
    An examination of the relationship between flowering times and temperature at the national scale using long-term phenological records from the UK (2000)
    Springer
    International journal of biometeorology 44 (2000), S. 82-87 
    Details
    ISSN: 1432-1254
    Keywords: Key words Flowering ; Phenology ; Climate change ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract  This paper examines the mean flowering times of 11 plant species in the British Isles over a 58-year period, and the flowering times of a further 13 (and leafing time of an additional 1) for a reduced period of 20 years. Timings were compared to Central England temperatures and all 25 phenological events were significantly related (P〈0.001 in all but 1 case) to temperature. These findings are discussed in relation to other published work. The conclusions drawn from this work are that timings of spring and summer species will get progressively earlier as the climate warms, but that the lower limit for a flowering date is probably best determined by examining species phenology at the southern limit of their distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004840000049
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  • 7
    Electronic Resource
    Electronic Resource
    Trends in phenological phases in Europe between 1951 and 1996 (2000)
    Springer
    International journal of biometeorology 44 (2000), S. 76-81 
    Details
    ISSN: 1432-1254
    Keywords: Key words Growing season ; Phenology ; Climate ; Change ; Time series ; Europe ; Germany
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract  Increases in air temperature due to the anthropogenic greenhouse effect can be detected easily in the phenological data of Europe within the last four decades because spring phenological events are particularly sensitive to temperature. Our new analysis of observational data from the International Phenological Gardens in Europe for the 1959–1996 period revealed that spring events, such as leaf unfolding, have advanced on average by 6.3 days (–0.21 day/year), whereas autumn events, such as leaf colouring, have been delayed on average by 4.5 days (+0.15 day/year). Thus, the average annual growing season has lengthened on average by 10.8 days since the early 1960s. For autumn events, differences between mean trends of species could not be detected, but for spring events there were differences between species, with the higher trends for leaf unfolding and flowering of shrubs indicating that changes in events occurring in the early spring are more distinct. These observed trends in plant phenological events in the International Phenological Gardens and results of other phenological studies in Europe, summarised in this study, are consistent with AVHRR satellite measurements of the normalized difference vegetation index from 1981 to 1991 and with an analysis of long-term measurements of the annual cycle of CO2 concentration in Hawaii and Alaska, also indicating a global lengthening of the growing season.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004840000054
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of seed size and emergence time on tree seedling establishment: importance of developmental constraints (2000)
    Springer
    Oecologia 123 (2000), S. 208-215 
    Details
    ISSN: 1432-1939
    Keywords: Key words Oak ; Walnut ; Seed size ; Emergence time ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  To evaluate the importance of developmental constraints in the determination of the relative importance of seed size and emergence time, early seedling performance of two woody species with contrasting growth phenology were observed under competitive conditions with tall herbs in an early successional habitat. The oak, Quercus mongolica var. grosseserrata, with determinate shoot development (a single leaf flush), showed a marked influence of seed size on subsequent seedling height growth and survival. Because of determinate growth, emergence time had negligible effects. The walnut, Juglans ailanthifolia, which continued to produce new leaves throughout the growing season (indeterminate development), showed a marked influence of time of emergence on seedling performance, because it affected the amount of growth that could be achieved; seed size, however, had negligible effects as the seedlings grew. These results suggest that relative importance of seed size and emergence time for early seedling performance is closely associated with developmental constraints (growth phenology).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420051007
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  • 9
    Electronic Resource
    Electronic Resource
    The interaction of season length and development time alters size at maturity (2000)
    Springer
    Oecologia 122 (2000), S. 51-59 
    Details
    ISSN: 1432-1939
    Keywords: Key words Life-history ; Phenology ; Sexual dimorphism ; Fitness ; Nephila clavipes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  An end-of-season penalty, with late-maturing individuals being smaller than early-maturing individuals, has been observed in a variety of univoltine terrestrial arthropods. The current study extends these observations, utilizing multiple populations of a single sexually dimorphic species to examine the ecological correlates and fitness consequences of late maturation at a small size. The orb-weaving spider, Nephila clavipes, inhabits a broad range of habitats that vary from mild to strong seasonality. Because males mature several instars earlier than females, they can reach maturity much earlier in the growing season. Within a cohort, I found that female size at maturity was negatively correlated with timing of maturation in strongly seasonal sites. At a less seasonal site, there was no correlation between female size and timing of maturation within a cohort. In most populations studied, male size was not correlated with the timing of maturation within a cohort. Within populations in strongly seasonal sites, late-maturing females had reduced fecundity. The probability of copulation, survivorship from maturity to first clutch, clutch size relative to female size, and the number of possible clutches were all reduced with delayed maturation. The probability of pre-reproductive death for late-maturing females was strongly affected by stochasticity in the timing of the end of the growing season.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00008835
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  • 10
    Electronic Resource
    Electronic Resource
    Predicting vegetative bud break in two arctic deciduous shrub species, Salix pulchra and Betula nana (2000)
    Springer
    Oecologia 124 (2000), S. 176-184 
    Details
    ISSN: 1432-1939
    Keywords: Key words Chilling ; Forcing ; Dormancy ; Phenology ; Tussock tundra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The factors controlling bud break in two arctic deciduous shrub species, Salix pulchra and Betula nana, were investigated using field observations and growth-chamber studies. A bud-break model was calibrated using a subset of the experimental observations and was used to predict bud break under current and potential future climate regimes. The two species responded similarly in terms of bud break timing and response to air temperature in both field and controlled environments. In the field, the timing of bud break was strongly influenced by air temperatures once snowmelt had occurred. Growth chamber studies showed that a period of chilling is required before buds break in response to warming. Model simulations indicate that under current conditions, the chilling requirement is easily met during winter and that even with substantial winter warming, chilling will be sufficient. In contrast, warm spring temperatures determine the timing of bud break. This limitation by spring temperatures means that in a warmer climate bud break will occur earlier than under current temperature regimes. Such changes in bud break timing of the deciduous shrubs will likely have important consequences for the relative abundance of shrubs in future communities and consequently ecosystem processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050005
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  • 11
    Electronic Resource
    Electronic Resource
    Temporal and geographical variations in grass pollen seasons in areas of west0ern Europe: an analysis of season dates at sites of the European pollen information system (2000)
    Springer
    Aerobiologia 16 (2000), S. 373-379 
    Details
    ISSN: 1573-3025
    Keywords: aerobiology ; airborne pollen ; Europe ; European Pollen Information ; Grass Pollen seasons ; Phenology ; start dates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Geographical and temporal variations in the start dates of grass pollen seasons are described for selected sites of the European Pollen Information Service. Daily average grass pollen counts are derived from Network sites in Finland, the Netherlands, Denmark, United Kingdom, Austria, Italy and Spain, giving a broad longitudinal transect over Western Europe. The study is part of a larger project that also examines annual and regional variations in the severity, timing of the peak and duration of the grass pollen seasons. For several sites, data are available for over twenty years enabling long term trends to be discerned. The analyses show notable contrasts in the progression of the seasons annually with differing lag times occurring between southern and northern sites in various years depending on the weather conditions. The patterns identified provide some insight into geographical differences and temporal trends in the incidence of pollinosis. The paper discusses the main difficulties involved in this type of analysis and notes possibilities for using data from the European Pollen Information service to construct pan European predictive models for pollen seasons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026521331503
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  • 12
    Electronic Resource
    Electronic Resource
    Phenological influences on the albedo of prairie grassland and crop fields (1999)
    Springer
    International journal of biometeorology 42 (1999), S. 153-157 
    Details
    ISSN: 1432-1254
    Keywords: Key words Albedo ; Phenology ; Solar zenith angle ; Prairie grassland ; Agricultural crops
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract  The albedo of land surfaces is strongly affected by transient surface conditions. For a vegetated surface, albedo can change with soil moisture, fractional canopy cover, and plant phenology as well as solar zenith angle (θs). In this study, the relationships between albedo and plant phenology in prairie grassland and agricultural crops were examined by removing the effect of variations in θs. Albedos were evaluated at a constant θs, which was assigned to be 20° in this study. For days with a minimum θs larger than 20°, a polynomial function that relates albedos to θs was derived and applied to estimate the albedos at 20°. After the removal of θs variations, the observed albedos of grassland at the Konza Prairie showed a linearly decreasing trend from spring to winter due to prairie phenology. The observed albedo of a maize field showed a clear increase from seedling to peak green stage, except when drought caused a decrease in near-infrared reflectance. The observed albedos of a winter wheat field showed an uninterrupted decrease from peak green to harvesting stage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004840050099
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  • 13
    Electronic Resource
    Electronic Resource
    Determining degree-day thresholds from field observations (1999)
    Springer
    International journal of biometeorology 42 (1999), S. 177-182 
    Details
    ISSN: 1432-1254
    Keywords: Key words Growing degree-days ; Kiwifruit ; Cherry trees ; Phenology ; Threshold temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract  This paper compares several methods for determining degree-day (°D) threshold temperatures from field observations. Three of the methods use the mean developmental period temperature and simple equations to estimate: (1) the smallest standard deviation in °D, (2) the least standard deviation in days, and (3) a linear regression intercept. Two additional methods use iterations of cumulative °D and threshold temperatures to determine the smallest root mean square error (RMSE). One of the iteration methods uses a linear model and the other uses a single triangle °D calculation method. The method giving the best results was verified by comparing observed and predicted phenological periods using 7 years of kiwifruit data and 10 years of cherry tree data. In general, the iteration method using the single triangle method to calculate °D provided threshold temperatures with the smallest RMSE values. However, the iteration method using a linear °D model also worked well. Simply using a threshold of zero gave predictions that were nearly as good as those obtained using the other two methods. The smallest standard deviation in °D performed the worst. The least standard deviation in days and the regression methods did well sometimes; however, the threshold temperatures were sometimes negative, which does not support the idea that development rates are related to heat units.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004840050102
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  • 14
    Electronic Resource
    Electronic Resource
    Persistent soil seed bank and standing vegetation at a high alpine site in the central Chilean Andes (1999)
    Springer
    Oecologia 119 (1999), S. 126-132 
    Details
    ISSN: 1432-1939
    Keywords: Key words Alpine zone ; Andes ; Phenology ; Seed bank ; Standing vegetation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The persistent soil seed bank (viable seeds 〉1 year) and standing vegetation were investigated in the upper alpine belt (3250 m) in the Andes of central Chile, 33° S. Nine species (eight in standing vegetation) were found in a total persistent seed bank of 899 seeds m−2. Seven additional species were represented by physically intact, non-viable seeds. Over 90% of the persistent seed bank was concentrated in Montiopsis sericea (Portulacaceae), Pozoa coriacea (Umbelliferae), Phacelia secunda (Hydrophyllaceae) and Oxalis compacta (Oxalidaceae). Examination of the seed/cover ratio revealed different propensities for persistent seed bank formation among species, and annuals formed persistent seed banks more frequently than perennial species. Abundance in the standing vegetation had predictive value for abundance in the persistent seed bank only when non-persistent seed bank species in the standing vegetation were discarded from the analysis. At the local scale, species diversity in the persistent seed bank and standing vegetation were correlated, but compositional similarity was low. Secondary down-slope dispersal promoted by frost heaving in combination with runoff, and life-form correlates are discussed as possible factors accounting for poor correspondence between the persistent seed bank and the standing vegetation at a local scale. The high Andean seed bank is similar to or larger than that reported for two Arctic tundra sites, but smaller than for a northern hemisphere subalpine site. If seed bank size is considered in relation to plant cover, the Andean seed bank greatly exceeds that of one Arctic site. Our study constitutes the first demonstration of a sizable persistent seed bank at an alpine site in the South American Andes and in southern hemisphere temperate mountains in general.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050768
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  • 15
    Electronic Resource
    Electronic Resource
    Evidence for stabilising selection acting on flowering time in Arum maculatum (Araceae): the influence of phylogeny on adaptation (1999)
    Springer
    Oecologia 119 (1999), S. 340-348 
    Details
    ISSN: 1432-1939
    Keywords: Key words Pollination ; Natural selection ; Diptera ; Phenology ; Phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between flowering time and reproductive success was investigated in the fly-pollinated, monoecious perennial herb Arum maculatum L. (Araceae). This species temporarily traps its principle pollinator, a psychodid midge. Probability of fruit set was analysed in relation to early, peak and late periods of the flowering phenology of four British populations between 1992 and 1997. In three out of five cases, plants which flowered during early and late periods were significantly less likely to set fruit. In addition, one population showed a similar relationship for percentage fruit set of individual inflorescences, and seeds from peak-flowering plants were significantly heavier. There was no variation in number of female flowers per inflorescence over the flowering season. Probability of fruit set appears to be mediated by the likelihood of trapping psychodid midges that have previously been trapped and picked up pollen, an unlikely event during early and late flowering periods when few inflorescences are open. The majority of plants in all populations produce only one inflorescence which means that timing of flowering may be crucial to reproductive success. We interpret our findings as evidence that stabilising selection may be acting on some populations and/or during some years. The ultimate cause, however, can be related to the very short (12–18 h) female phase of each inflorescence, a phylogenetically conservative trait within the Araceae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050794
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  • 16
    Electronic Resource
    Electronic Resource
    Restructuring of Lepidoptera communities by introduced Vespula wasps in a New Zealand beech forest (1999)
    Springer
    Oecologia 119 (1999), S. 565-571 
    Details
    ISSN: 1432-1939
    Keywords: Key wordsVespula ; Lepidoptera ; Phenology ; Shared predator ; Ecological impact
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Introduced social wasps (Vespula vulgaris) reach high densities in some New Zealand beech forests, because honeydew provides an abundant high-energy food source. We manipulated wasp density to estimate an “ecological damage threshold” for large, free-living Lepidoptera larvae. There will be a continuum of ecological damage thresholds for wasp density depending on the prey species or habitat. Experimentally placed small caterpillars had a significantly higher survival rate than large caterpillars, and the survival rate of both groups decreased with increasing wasp density. Spring-occurring caterpillars have a probability of surviving of 0.90–0.95, assuming wasps are the only source of mortality. However, at the peak of the wasp season we predict caterpillars would have virtually no chance (probability of 10−78 to 10−40) of surviving to adults. Wasp abundance must be reduced by at least 88% to conserve the more vulnerable species of free-living caterpillars at wasp densities similar to those observed in our study sites. This equates to a damage threshold of 2.7 wasps per Malaise trap per day. It was exceeded for about 5 months of the year in non-poisoned sites. There are currently no biological or chemical control techniques available in New Zealand that will reduce wasp abundance below this damage threshold throughout the year. Our models show that most Lepidoptera with spring caterpillars will be able to persist, but species with caterpillars occurring in the peak wasp season will be eliminated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050820
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  • 17
    Electronic Resource
    Electronic Resource
    Temporal and spatial variation of litter production in Sonoran Desert communities (1999)
    Springer
    Plant ecology 145 (1999), S. 37-48 
    Details
    ISSN: 1573-5052
    Keywords: Desertscrub ; Ecosystem ; Litterfall ; Mexico ; Phenology ; Spatial heterogeneity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The seasonal pattern of litter production was analyzed in three contiguous desert communities near the southern boundaries of the Sonoran Desert. There was a large spatial variation in annual litter production mainly caused by differences in the composition and structure of vegetation. In the most productive site (Arroyos) annual litterfall was 357 g m-2yr-1, a figure higher than some tropical deciduous forests. Litter production was only 60g m-2yr-1in the open desert in the plains (Plains) and 157 g m-2yr-1 in the thornscrub on the slopes (Hillsides). Topographic and hydrologic features influence the composition, structure and function of the vegetation, modifying the general relationship between rainfall and productivity described for desert ecosystems. The temporal pattern of litter production showed marked seasonality with two main periods of heavy litterfall: one after the summer rains from September to November (autumn litter production) and another after the winter rains from March to May (spring litter production). In the open desert areas, spring litter production was significantly higher than the autumn pulse, while in the slopes, the autumn production was the most important. The Arroyos site produced similar litterfall amounts during the two dry seasons. The species composition defined the season of maximum leaf-fall. In the Plains, the vigorous winter growth of ephemeral and perennial plants made up most of the litter production, while in the Hillsides, most perennials remained dormant throughout the winter-spring period and a significant peak of litterfall occurred only after the summer growth. This difference in growth between seasons was less pronounced in the Arroyos. The timing of maximum production of reproductive and woody litter also differed from site to site.
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    URL: http://dx.doi.org/10.1023/A:1009896201047
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    Defining grassland fire events and the response of perennial plants to annual fire in temperate grasslands of south-eastern Australia (1999)
    Springer
    Plant ecology 144 (1999), S. 127-144 
    Details
    ISSN: 1573-5052
    Keywords: Life form ; Phenology ; Secondary juvenile period ; Themeda triandra ; Vegetative regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Many species-rich Themeda triandra grasslands in south-eastern Australia have been burnt annually in summer as a land management practice for decades. The characteristics of annual fires (maximum surface temperatures, maximum soil temperature changes at 10 mm depth, Byram fire intensity and duration of surface heating) were compared to fires that occur less frequently (2, 4 or 7-year inter-fire interval). The impacts of annual summer fires on seed survival, perennial plant dynamics and flowering were also documented at two sites over two years. Annual grassland fires differ principally from other grassland fire types in their duration of surface temperatures above 100 °C (i.e., 〈1 min versus 〉2–3 min in grasslands burnt at 4–7-year intervals). This was correlated to fuel load, but not rate of spread or Byram fire intensity. Maximum surface temperatures were variable within annual fire events (98–458 °C ) and did not differ significantly from those observed in other grassland fires. All sites experienced temperatures above 350 °C but no site had its soil temperature increase at 10 mm depth by 〉10 °C during fire. Byram fire intensity was lower in annually burnt sites, but positively correlated with rate of spread moreso than fuel load. Many perennial species (34–55%) and most perennial individuals (70–83%) avoid the annual summer fire event by being dormant at the time of burning. All perennial species regenerated rapidly by vegetative means after fire and seedlings were absent or rare for most species. As a result, turnover of species at the small-scale was low. Annual burning permits high perennial species richness (mean 18 species/0.25 m2) and high numbers of individual perennial plants (range 189–1036 plants/0.25 m2) to co-exist at the small-scale. Seasonal plant density maxima peaked in spring, 6–8 months after fire, and the number of plants in a species' population each year following fire depended on their seasonal response more than their direct fire response. The direction and magnitude of population change from one year to the next was species and site specific and did not correlate with life form or a plant's ability for vegetative spread. All perennial species have a short secondary juvenile period (i.e., 6–11 months) but relatively few individual plants flower in any one year. Seed that has made its way into the soil is completely protected from the direct effects of fire and hence, occasional post-fire seedling recruitment may be possible for all species. Maintaining annual burning in grasslands as a management regime is unlikely to lead to a decline in richness and plant density in the short-term. Rather, delayed burning (i.e., 〉3 year intervals), and the impact that this may have on interval dependent processes such as above-ground competition, are predicted to have more substantial long-term effects on the small-scale dynamic of this community.
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    URL: http://dx.doi.org/10.1023/A:1009731815511
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    Flower development and reproductive continuity in MediterraneanRuscus aculeatus L. (Liliaceae) (1999)
    Springer
    Protoplasma 208 (1999), S. 58-64 
    Details
    ISSN: 1615-6102
    Keywords: Fruit persistence ; Bud morphology ; Ruscus aculeatus ; Dioecy ; Mediterranean species ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ruscus aculeatus is a subandroecious species widespread in Mediterranean environments. Our studies on floral differentiation show that the unisexual flowers pass through a stage in which both androecial and gynoecial primordia are initiated. The hypothesis that dioecy has arisen secondarily from hermaphroditism is discussed. Data on flowering phenology of Mediterranean populations ofR. aculeatus showed it has a long flowering season (about 7 months). This phenology is similar to that of the Mediterranean species originated before the development of the Mediterranean climate. Members of the family Ruscaceae where present in Laurasia during the tropical Tertiary and the present study on flower and fruit morphology and reproductive phenology reveals forR. aculeatus a list of characters generally reported for tropical species. Small and greenish flowers, fleshy fruits, few large seeds, and resprouting capacity, together with long flowering season and continuous availability of ripe fruits, occur all together inR. aculeatus. It constitutes a “tropical reproductive syndrome” which might have survived the climatic fluctuations of the Quaternary, the establishment of the Mediterranean climate, and the present anthropogenic disturbs.
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    URL: http://dx.doi.org/10.1007/BF01279075
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    The effect of nutrition on the seasonal course of needle respiration in Norway spruce stands (1998)
    Springer
    Trees 12 (1998), S. 130-138 
    Details
    ISSN: 0931-1890
    Keywords: Key words Carbohydrates ; Fertilisation ; Phenology ; Picea abies ; Q10 of respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Respiration of 1-year-old needles of 30-year-old Norway spruce trees [Picea abies (L.) Karst.] was studied in a nutrient optimisation experiment in northern Sweden. Respiration rates of detached needles, from ten control (C) and ten irrigated-fertilised (IL) trees, were measured on 16 occasions from June 1992 to June 1993. The aim of the study was to determine the influence of temperature on the seasonal course of needle maintenance respiration, and the effect of nitrogen concentration [N] and carbohydrate content on needle respiration in young Norway spruce trees subjected to long-term fertilisation. The IL treatment significantly affected needle size, in terms of dry mass and length, but not specific needle length (SNL). There was, however, a strong tree-specific effect on SNL (P〈10–9, R 2 = 0.75). Needle starch content varied markedly with season (0–25% of total dry mass). This, unless accounted for, would cause erroneous estimates of nutrient concentrations, and of rates of needle respiration, within and between treatments. There was considerable seasonal variation in needle respiration, both in terms of maintenance respiration and temperature dependence (Q10). Q10 had its highest value (2.8) during winter and its lowest (2.0) in the middle of summer. In early autumn (August, September), respiration rate and needle [N] were significantly related (C: P = 0.001, IL: P〈0.0005). There was no significant difference in the slope between the two regression lines, but a difference in intercept. At the same needle [N], needles from IL-plots always had a lower respiration rate than needles from control plots. No obvious explanation for the observed difference in intercept was found, but some plausible assumptions are put forward and discussed.
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    URL: http://dx.doi.org/10.1007/s004680050131
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    Effects of elevated CO2 on flowering phenology and nectar production of nectar plants important for butterflies of calcareous grasslands (1998)
    Springer
    Oecologia 113 (1998), S. 341-349 
    Details
    ISSN: 1432-1939
    Keywords: Key words Elevated CO2 ; Phenology ; Nectar ; Sugar ; Amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Effects of elevated CO2 on flowering phenology and nectar production were investigated in Trifolium pratense, Lotus corniculatus, Scabiosa columbaria, Centaurea jacea and Betonica officinalis, which are all important nectar plants for butterflies. In glasshouse experiments, juvenile plants were exposed to ambient (350 μl l−1) and elevated (660 μl l−1) CO2 concentrations for 60–80 days. Elevated CO2 significantly enhanced the development of flower buds in C. jacea. B. officinalis flowered earlier and L. corniculatus produced more flowers under elevated CO2. In contrast, the number of flowers decreased in T. pratense. The amount of nectar per flower was not affected by elevated CO2 in the tested legumes (T. pratense and L. corniculatus), but was significantly reduced (!) in the other forbs. Elevated CO2 did not significantly affect nectar sugar concentration and composition. However, S. columbaria and C. jacea produced significantly less total sugar under elevated CO2. The nectar amino acid concentration remained unaffected in all investigated plant species, whereas the total of amino acids produced per flower was reduced in all non-legumes. In addition, the amino acid composition changed significantly in all investigated species except for C. jacea. The observed effects are unexpected and are a potential threat to flower visitors such as most butterflies which have no alternative food resources to nectar. Changes in nectar production due to elevated CO2 could also have generally detrimental effects on the interactions of flowers and their pollinators.
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    URL: http://dx.doi.org/10.1007/s004420050385
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    The effect of canopy cover and seasonal change on host plant quality for the endangered Karner blue butterfly (Lycaeidesmelissasamuelis) (1998)
    Springer
    Oecologia 114 (1998), S. 243-250 
    Details
    ISSN: 1432-1939
    Keywords: Key wordsHost plant quality ; Lupinusperennis ; Phenology ; Shade ; Butterfly conservation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Larvae of the Karner blue butterfly, Lycaeidesmelissasamuelis, feed solely on wild lupine, Lupinusperennis, from the emergence to summer senescence of the plant. Wild lupine is most abundant in open areas but Karner blue females oviposit more frequently on lupines growing in moderate shade. Can differences in lupine quality between open and shaded areas help explain this disparity in resource use? Furthermore, many lupines are senescent before the second larval brood completes development. How does lupine senescence affect larval growth? We addressed these questions by measuring growth rates of larvae fed lupines of different phenological stages and lupines growing under different shade conditions. The habitat conditions under which lupines grew and plant phenological stage did not generally affect final larval or pupal weight but did significantly affect duration of the larval period. Duration was shortest for larvae fed leaves from flowering lupines and was negatively correlated with leaf nitrogen concentration. Ovipositing in areas of moderate shade should increase␣second-brood larval exposure to flowering lupines. In addition, larval growth was significantly faster on shade-grown lupines that were in seed than on similar sun-grown lupines. These are possible advantages of the higher-than-expected oviposition rate on shade-grown lupines. Given the canopy-related trade-off between lupine␣abundance and quality, maintenance of canopy heterogeneity is an important conservation management goal. Larvae were also fed leaves growing in poor soil conditions and leaves with mildew infection. These and other feeding treatments that we anticipated would inhibit larval growth often did not. In particular, ant-tended larvae exhibited the highest weight gain per amount of lupine eaten and a relatively fast growth rate. This represents an advantage of ant tending to Karner blue larvae.
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    URL: http://dx.doi.org/10.1007/s004420050442
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    Delayed induced changes in the biochemical composition of host plant leaves during an insect outbreak (1998)
    Springer
    Oecologia 116 (1998), S. 182-190 
    Details
    ISSN: 1432-1939
    Keywords: Key wordsBetula pubescens ; Gallotannins ; Induced resistance ; Leaf biochemistry ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In birch, Betula pubescens, herbivore-induced delayed induced resistance (DIR) of defoliated trees may cause a strong reduction in the potential fecundity of a geometrid folivore Epirrita autumnata. In this study, we examined the biochemical basis of DIR in birch leaves during a natural outbreak of E. autumnata. A set of experimental trees was defoliated at four sites by wild larvae in the peak year of the outbreak, whereas control trees were protected from defoliation by spraying with an insecticide. The biochemical composition of leaves was analysed in the following year and, although the DIR response was weak during this outbreak, causing less than a 20% reduction in the potential fecundity of E. autumnata, some consistent relationships between defoliation, biochemistry and pupal mass of E. autumnata suggested a general biochemical basis for the defoliation-induced responses in birch leaves. Total concentrations of nitrogen, sugars and acetone-insoluble residue (e.g. cell wall polysaccharides, cell-wall-bound phenolics, protein, starch, lignin and hemicellulose) were consistently lower, and total concentrations of phenolics, especially of gallotannins and soluble proanthocyanidins, were higher in the leaves of trees defoliated in the previous year than in those protected from defoliation. The capacity of tannins to precipitate proteins correlated with contents of gallotannins, and was highest in defoliated trees. The pupal mass of E. autumnata showed a strong, positive correlation with concentrations of nitrogen and sugars, and a negative correlation with the acetone-insoluble residue and gallotannins in foliage. Correlations with other measured biochemical traits were weak. The correlation coefficients between biochemical traits and pupal mass consistently had similar signs for both defoliated and insecticide–sprayed trees, suggesting that variation in leaf quality due to defoliation in the previous year was based on similar biochemical traits as variation for other reasons. We suggest that DIR is associated with reduced growth activity of leaves, and may be seen as a delay in the biochemical maturation of leaves in defoliated trees. This explains the high concentration of gallotannins in defoliated trees, a characteristic feature of young leaves. However, the lower content of nitrogen and the higher content of soluble proanthocyanidins in defoliated trees are traits usually characterising mature, not young, leaves, indicating defoliation-induced changes in chemistry in addition to modified leaf age. Our results emphasise the importance of understanding the natural changes in chemistry during leaf maturation when interpreting defoliation-induced changes in leaf biochemistry.
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    URL: http://dx.doi.org/10.1007/s004420050578
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    Sexual specialization in two tropical dioecious figs (1998)
    Springer
    Oecologia 115 (1998), S. 391-400 
    Details
    ISSN: 1432-1939
    Keywords: Key words Agaonidae ; Dioecy ; Mutualism ; Phenology ; Pollination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ficus species (figs) and their species-specific pollinator wasps are involved in an intimate mutualism in which wasps lay eggs in some ovaries of the closed inflorescences (syconia), and mature, inseminated offspring carry pollen from mature syconia to fertilize receptive inflorescences. In monoecious species, each syconium produces seeds and wasps. In functionally dioecious fig species, making up approximately half the figs worldwide, male and female functions are separated; hermaphrodite (functionally male) trees produce wasps and pollen only, while female trees produce seeds only. This sexual separation allows selection to act independently on the reproductive biology of each sex. Examining sexual specialization in a tight mutualism allows us to determine aspects of the mutualism that are flexible and those that are canalized. In this study, we quantified the phenology of two species of dioecious figs, F. exasperata and F. hispida, for 2 years by following the fates of several thousand syconia over time. In studying each of these species in a dry and a wet site in south India, we tested specific predictions of how dioecious figs might optimize sexual function. On female trees of both species, more inflorescences matured during the wet (monsoon) season than in any other season; this fruiting period enabled seeds to be produced during the season most suitable for germination. In F. exasperata, functionally male trees released most wasps from mature syconia in the dry season, during peak production of receptive female syconia, and thus maximized successful pollination. In F. hispida, “male” trees produced more syconia in the dry and monsoon seasons than in the post-monsoon season. In both species, male and female trees abscised more unpollinated, young inflorescences than pollinated inflorescences, but abscission appeared to be more likely due to resource- rather than pollinator- limitation. The phenology of F. exasperata requires that male inflorescences wait in receptive phase for scarce pollinators to arrive. As expected, male inflorescences of this species had a longer receptive phase than female inflorescences. In F. hispida, where pollinators are rarely scarce, duration of receptive phase was the same for both sexes. Duration of developing phase was longer in female syconia of both species than in male syconia, most likely because they need a longer period of investment in a fleshy fruit. Variation in developing phase of female syconia in one species (F. exasperata) was also greater than that in male syconia, and enabled female trees to sample a variety of germination environments in time. The strong sexual differences in both fig species support the hypothesis that selection for sexual specialization has strongly influenced the reproductive biology of these species.
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    URL: http://dx.doi.org/10.1007/s004420050533
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    Seasonality of sap-sucking insects (Auchenorrhyncha, Hemiptera) feeding on Ficus (Moraceae) in a lowland rain forest in New Guinea (1998)
    Springer
    Oecologia 115 (1998), S. 514-522 
    Details
    ISSN: 1432-1939
    Keywords: Key words Herbivores ; Host specificity ; Insect abundance ; Phenology ; Species diversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sap-sucking insects (Auchenorrhyncha, Hemiptera) were sampled quantitatively from the foliage of 15 species of Ficus (Moraceae) in a lowland rain forest in Papua New Guinea. Continuous sampling throughout 12 months produced 61,777 individuals and 491 species. Two seasonality parameters, circular statistics and Lloyd's index, were calculated for 139 species with a sample size of more than 36 individuals. Most of the species were present in the adult stage for at least half of the year, and many of them continuously throughout the year. However, almost all species exhibited marked seasonal changes in abundance. The abundance peaks of species were scattered throughout most of the year, but more species reached their population maximum during the wet, especially early wet, season than during the dry season. Overall species richness and abundance of Auchenorrhyncha were also higher during the wet than the dry season. A significant correlation between seasonality and host specificity was revealed in the auchenorrhynchan community. In particular, species evenly distributed throughout the year had a tendency to feed on a larger number of Ficus species than seasonally more restricted species. The seasonality, and the seasonality versus specificity correlation, were independent of species abundance. Among the most abundant species (n 〉 300) there was a marginally significant negative correlation between abundance and host specificity, so that polyphagous species had, on average, larger populations than specialists. There was no similar correlation among rarer species. The Auchenorrhyncha comprises three feeding guilds, which were also analysed separately. The mesophyll-feeding guild exhibited more pronounced seasonality than the phloem- and xylem-feeders. This difference could be explained as a part of the overall correlation between seasonality and host specificity as mesophyll-feeders were significantly more host specific than the other two guilds.
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    URL: http://dx.doi.org/10.1007/s004420050549
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    Seasonal patterns of gas exchange, water relations and growth of it Roupala montana, an evergreen savanna species (1998)
    Springer
    Plant ecology 136 (1998), S. 69-76 
    Details
    ISSN: 1573-5052
    Keywords: Cerrado ; Phenology ; Photosynthesis ; Stomatal conductance ; Water stress ; Water-use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Roupala montana is an evergreen species widespread in the seasonal savannas of the central plains of Brazil. I examined the degree of coupling of photosynthetic gas-exchange characteristics, water relations and growth responses of R. montana with regard to seasonal changes in soil water availability. Despite a rainless period of over three months soil water potential at 60 cm depth reached values of only about -1.0 MPa, while pre-dawn leaf water potential (Ψl) reached about -0.4 MPa by the end of the three-month drought. Thus, R. montana had access to deep soil water in the dry period, but pre-dawn Ψl did not reach the high wet season values of -0.2 MPa. Most of the shoot growth was concluded in the onset of the rainy season. Although some individual branches might have shown some extension thereafter, most of them remained inactive during the rest of the rainy season and the subsequent dry season. New leaf production was also restricted to the first part of the wet period. R. montana remained evergreen in the dry season, but there was a 27% decrease in the number of leaves and herbivory removed about 16% of the leaf area still present in the plant. CO2-exchange rates of these leaves reached only ca. 55% of the maximum rainy season values of 14 µmol m-2 s-1. Thus, the estimated potential daily carbon gain was about 34% of the maximum by the end of the dry period. These values will be even lower, if we considered the decrease in photosynthetic rates that occurred around midday. These reductions in photosynthetic rates as a result of partial stomatal closure were measured both in the wet and dry season and they were related to increases in the evaporative demand of the atmosphere. In conclusion, the combined effect of herbivory, leaf loss and reductions in photosynthetic rates limited plant productivity in the dry season.
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    URL: http://dx.doi.org/10.1023/A:1009763328808
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    Timing and spatial patterning of seed dispersal and redistribution in a South American warm desert (1998)
    Springer
    Plant ecology 137 (1998), S. 143-150 
    Details
    ISSN: 1573-5052
    Keywords: Argentina ; Granivory ; Monte Desert ; Newly-produced seeds ; Phenology ; Seed bank ; Seed dispersal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We measured newly-produced seeds entering the soil (Potential Seed Bank) to assess the timing and spatial patterning of Phase I dispersal in the central Monte desert, Argentina. Rates of forb- (6.13 mg m-2 d-1) and shrub-seed input (48.9 mg m-2 d-1) were maximum in early summer. The rate of grass-seed input, instead, was similar in early and late summer (7 to 8 mg m-2 d-1). About 90% of forb- and shrub-seed mass entered the habitat through protected (i.e., under canopy) areas, whereas 70% of grass-seed mass did so through exposed areas. Adult plant location and the uneven impact of wind on shrub, forb and grass seeds may explain such patterns. We also compared the Potential Seed Bank with the soil seed bank in the following spring (Realized Seed Bank). Seeds that form transient banks in other ecosystems (e.g., shrub seeds of the genus Larrea, or perennial grass seeds like those of Pappophorum and Trichloris) prevailed in the Potential Seed Bank. Some annual forb seeds, instead, appeared to form a more persistent seed bank, and prevailed in the Realized Seed Bank (e.g., Chenopodium). Horizontal redistribution did not affect the spatial patterning of forb and shrub seeds, but produced a more homogeneous distribution of grass seeds in the habitat. The impact of wind could explain the redistribution pattern of grass seeds. Finally, we found almost 80% of total seeds in the top 2 cm of soil. The smallest grass and forb seeds (Sporobolus and Descurainia) as well as some medium-sized and large forb seeds (e.g., Glandularia, Sphaeralcea, Phacelia) were able to reach deeper soil layers in the central Monte desert.
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    URL: http://dx.doi.org/10.1023/A:1009776601012
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    Latitudinal variation in the fruiting phenology of a bird-dispersed plant (shape Crataegus monogyna) in Western Europe (1998)
    Springer
    Plant ecology 137 (1998), S. 139-142 
    Details
    ISSN: 1573-5052
    Keywords: Crataegus ; Frugivory ; Fruit ripening ; Latitude ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A number of fleshy-fruit-bearing plants of temperate regions are dispersed by migratory frugivorous birds. It has been suggested that the more southerly populations of such species should produce ripe fruits later than more northerly populations, to ensure that fruit is available when the birds arrive. I will call this the ‘adaptive delay’ hypothesis. To test this hypothesis, I monitored fruiting phenology of Crataegus monogyna Jacq. at ten sites (in all of which fruit consumption is very largely by redwings, Turdus iliacus, and fieldfares, Turdus pilaris) between northern Spain (42° N) and northern Scotland (59° N). There was no negative correlation between latitude and date of fruit ripening (earliest recorded date on which ripe fruits had appeared, or earliest recorded date by which all fruits had ripened). My results thus argue against the adaptive delay hypothesis.
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    URL: http://dx.doi.org/10.1023/A:1009712000104
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    Vegetative propagation and sexual reproduction in the woodland understorey pseudo-annual Circaea lutetiana L. (1998)
    Springer
    Plant ecology 134 (1998), S. 211-224 
    Details
    ISSN: 1573-5052
    Keywords: Clonal plant ; Development ; Forest ; Hibernacle ; Phenology ; Trade-off
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract On the forest floor of deciduous woodlands, relative light intensity gradually declines during the early growing season. The woodland understorey pseudo-annual Circaea lutetiana L. completes its life-cycle at the end of summer. These pseudo-annuals are clonal plants which survive the winter only as seeds and as hibernacles produced by the rhizome apices. In this paper, we asked several questions related to the life-history of C. lutetiana. It was found that shoot formation in early spring did not exhaust the old hibernacle. A trade-off between rhizome + hibernacle number and weight might be expected when plants grow under resource limitation. It was hypothesised that both number and weight of rhizomes and hibernacles will be affected by light availability. Since the effect of resource supply on the size number trade-off will depend on the developmental pattern of the rhizome system, rhizome development was studied as well. Soon after the shoots emerged, 1st order rhizomes were formed in May on the nodes of the old hibernacle. First-order rhizomes branched in June and 2nd order rhizomes (side-branches) were continuously produced throughout the growing season. The phenology and developmental rate of plants growing in different light treatments were plastic. On average 30% of rhizome biomass was formed during the vegetative phase, and rhizome and fruit production were only partly separated in time. The ratio of total rhizome biomass to total fruit biomass was not affected by light. Also flower bud removal did not lead to an increase in rhizome production, which suggests that division of biomass to both reproductive modes is rather rigid. The number of 1st order rhizomes was not affected by the light treatments. Under light limitation, both rhizome number and weight of single rhizomes were reduced. In contrast, fruit number, but not weight of single fruits, was limited.
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    URL: http://dx.doi.org/10.1023/A:1009741102627
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    Timing of deacclimation affects the ability to recover from simulated winter herbivory (1998)
    Springer
    Plant ecology 135 (1998), S. 9-12 
    Details
    ISSN: 1573-5052
    Keywords: Climate change ; Phenology ; Regrowth ; Vaccinium ; Winter herbivory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ability of Vaccinium myrtillus L. to recover from simulated winter herbivory has been investigated on different plants which had been exposed to three elevated temperatures (5 °C, 10 °C or 20 °C) for four weeks in a greenhouse environment. After herbivory, number and length of new aerial shoots and number of leaves/shoot increased faster in plants kept at 5 °C and 10 °C than in those kept at 20 °C. In the following autumn, however, only the shoot number differed between treatments, being greatest in plants of treatments at 5 °C and 10 °C and lowest at 20 °C and the outdoor control. Apparently the plants kept at 20 °C had already used their resources for growth before herbivory simulation, which reduced their recovery ability thereafter. In addition, the growing season was too short for the control plants to produce as many new shoots as the treatments. The results show that the recovery of V. myrtillus from winter herbivory is rapid if it occurs before growth has started. Hence the earlier onset of spring as a consequence of climate warming may not be fatal for the plant, unless the temperature increase triggers growth to start many months earlier than normal.
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    URL: http://dx.doi.org/10.1023/A:1009784917648
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    Perception of shape from shading in chimpanzees (Pan troglodytes) and humans (Homo sapiens) (1998)
    Springer
    Animal cognition 1 (1998), S. 25-35 
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    ISSN: 1435-9456
    Keywords: Key words Shape from shading ; Visual search ; Texture segregation ; Chimpanzees ; Humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The perception of shape from shading was tested in two chimpanzees (Pan troglodytes) and five humans (Homo sapiens), using visual search tasks. Subjects were required to select and touch an odd item (target) from among uniform distractors. Humans found the target faster when shading was vertical than when it was horizontal, consistent with results of previous research. Both chimpanzees showed the opposite pattern: they found the target faster when shading was horizontal. The same difference in response was found in texture segregation tasks. This difference between the species could not be explained by head rotation or head shift parallel to the surface of the monitor. Furthermore, when the shaded shape was changed from a circle to a square, or the shading type was changed from gradual to stepwise, the difference in performance between vertical and horizontal shading disappeared in chimpanzees, but persisted in humans. These results suggest that chimpanzees process shading information in a different way from humans.
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    Effects of seasonal rainfall on radial growth in two tropical tree species (1997)
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    International journal of biometeorology 41 (1997), S. 13-16 
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    ISSN: 1432-1254
    Keywords: Key words Climate variation ; Drought stress ; Growth models ; Phenology ; Tropical dendroecology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract  Seasonal drought may limit primary productivity in most of the tropics, but the determinants of tree growth are not well known. A 10-year study of the deciduous trees Cochlospermum vitifolium (Willd.) Spreng. (Cochlospermaceae) and Cnidoscolus spinosus Lundell (Euphorbiaceae) in southwestern México showed radial growth to be highly correlated (both r〉0.85) only with precipitation during an interval of 〈2 months in the mid-wet season. Growth was not affected by total annual precipitation or by an early starting or late ending of the wet season, or by heavy rainfall in the dry season. Annual mean girth increments ranged from 0.03 to 3.31 cm and −0.1 to 2.01 cm, respectively. The best model for growth (r 2〉0.85) was a linear combination of mid-summer precipitation (positive coefficient) and total precipitation over the previous 2 years (negative coefficient). Comparison with other species showed heterogeneous responses of wood production to climate variation, and suggests that the range of functional types of dry forest trees is still unknown.
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    URL: http://dx.doi.org/10.1007/s004840050047
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    Simulation models for European corn borer postdiapause morphogenesis and early infestation of maize in Missouri, USA (1997)
    Springer
    International journal of biometeorology 40 (1997), S. 128-134 
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    ISSN: 1432-1254
    Keywords: Key words European corn borer ; Maize ; Postdiapause ; Phenology ; Infestation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract  The European corn borer is one of the most damaging insect pests to maize in the United States. Different methods exist for the estimation of time of damage to corn by first generation European corn borer. The most commonly used method is the linear thermal constant concept of phenology which by convention calculates cumulative thermal units from January 1 or another arbitrary date. Linear and nonlinear models based on the thermal units concept developed were to predict and simulate postdiapause development of the European corn borer and subsequent infestation of the maize crop using early spring temperatures (May 1–15) in central Missouri. The developmental rates of European corn borer were obtained from growth chamber investigations that simulated those temperatures, the operational temperatures being selected from a compilation of archival meteorological data from 1948 to 1989. The linear and polynomial regression models were developed to predict phenological stages of the European corn borer using thermal units as developmental rates. The models were compared against each other to determine the better predictor of estimation values: each explained 94 and 98% of the variation in developmental stages, respectively. In addition, the models were tested against independent field data and both models gave good predictions of developmental stages, indicating that either model would be a good predictor.
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    Rainfall, food abundance and timing of parturition in African bats (1997)
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    Oecologia 111 (1997), S. 309-317 
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    ISSN: 1432-1939
    Keywords: Key words Chiroptera ; Food abundance ; Parturition ; Phenology ; Reproduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We used published results from studies in Africa to test the hypothesis that the timing of parturition in the Chiroptera is constrained by rainfall. Comparison of year-round rainfall and insect data at various latitudes showed that insect abundance peaks approximately a month after peak rainfall. A similar comparison of parturition time to rainfall showed that with the possible exception of the molossids, the Microchiroptera commonly give birth a month before peak rainfall. With an average 6-week lactation period in the Microchiroptera, the timing of parturition is such that young bats are weaned just before the period of maximum insect abundance. We suggest that the needs of the young in this post-weaning period may be more important than the energetic demands of lactation on the mother in determining the timing of parturition on an evolutionary scale. A similar conclusion is implied for the African Megachiroptera, but there is insufficient information on their reproduction to adequately test the main hypothesis for these bats.
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    Altitudinal life history variation in the dung flies Scathophaga stercoraria and Sepsis cynipsea (1997)
    Springer
    Oecologia 109 (1997), S. 342-352 
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    ISSN: 1432-1939
    Keywords: Key words Body size ; Development ; Phenology ; Phenotypic plasticity ; Season length
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Field phenologies of high- (ca. 1500 m) and low- (ca. 500 m) altitude populations of the two most common European species of dung flies, Scathophaga stercoraria and Sepsis cynipsea, differ quite markedly due to differences in climate. To differentiate genetic adaptation due to natural selection and phenotypic plasticity, I compared standard life history characters of pairs of high- and low-altitude populations from three disjunctive sites in Switzerland in a laboratory experiment. The F1 rearing environment did not affect any of the variables of the F2 generation with which all experiments were conducted; hence, there were no carry-over or maternal effects. In Sc. stercoraria, high-altitude individuals were smaller but laid larger eggs; the latter may be advantageous in the more extreme (i.e. more variable and less predictable) high-altitude climate. Higher rearing temperature strongly decreased development time, body size and the size difference between males and females (males are larger), produced female-biased sex ratios and led to suboptimal adult emergence rates. Several of these variables also varied among the three sites, producing some interactions complicating the patterns. In Se. cynipsea, high-altitude females were marginally smaller, less long-lived and laid fewer clutches. Higher rearing temperature strongly decreased development time and body size but tended to increase the size difference between males and females (males are smaller); it also increased clutch size but decreased physiological longevity. Again, interpretation is complicated by variation across sites and some significant interactions. Overall, genetic adaptation to high-altitude conditions appears weak, probably prevented by substantial gene flow, and may be swamped by the effects of other geographic variables among populations. In contrast, phenotypic plasticity is extensive. This may be due to selection of flexible, multi-purpose genotypes. The results suggest that differences in season length between high- and low-altitude locations alone do not explain well the patterns of variation in phenology and body size.
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    Leaf growth and demography of the rheophytic fern Thelypteris angustifolia (Willdenow) Proctor in a Puerto Rican rainforest (1997)
    Springer
    Plant ecology 130 (1997), S. 203-212 
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    ISSN: 1573-5052
    Keywords: Fern sporophyte ; Leaf expansion ; Leaf longevity ; Luquillo Experimental Forest ; Phenology ; Sterile-fertile leaf dimorphy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Morphological and temporal aspects of the growth of leaves of Thelypteris angustifolia (Willdenow) Proctor are under study along a 400-m section of the Sonadora River at the El Verde Field Station in the Luquillo Experimental Forest of Puerto Rico. Emergence, expansion and growth of leaves of 149 sporophytes have been observed approximately mid-month every January, May and September since September 1991. Results of the first four years of this long-term study of T. angustifolia are reported here. Although they are land plants, sporophytes of T. angustifolia are rheophytic, subject to intermittent flooding and submerged approximately 7% of the time. The pinnate leaves of T. angustifolia exhibit sterile-fertile leaf dimorphy. Only 7.6% of the leaves in the the sample were fertile. The petiole of a fertile leaf was 41% longer than that of a sterile leaf while leaf blades were the same length. Leaves expanded at a mean rate of 1.7 cm per day, maturing in 29.7 days. Mean leaf life span was 10.8 months with a maximum of 26 months. Sterile leaf longevity (11.0 months) was longer than that of the fertile leaf (9.6 months). Leaves were produced at a mean rate of 4.7 leaves per plant per year. Leaf damage occurred on 38% of the leaves observed. Net leaf counts for individual sporophytes ranged from one to eight with a mean of 3.0 leaves per plant. Fertile plants had higher mean leaf counts (4.1) than plants without fertile leaves (2.8). Leaf production, although possibly triggered by increasing daylength, also paralleled seasonal increases in rainfall during the wetter mid-May/September months. Increased leaf mortality occurred during the drier mid-January/May period.
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    Survival curves and longevity of the leaves of Alnus japonica var. arguta in Kushiro Marsh (1996)
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    Plant ecology 124 (1996), S. 61-66 
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    ISSN: 1573-5052
    Keywords: Alder trees ; Alnus japonica ; Kushiro Marsh ; Leaf longevity ; Leaf survival ; Marsh forest ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The seasonal changes in leaf emergence and leaf-fall in a Japanese alder stand of the fen in Kushiro Marsh were studied, and survival curves for the leaves were drawn. Leaves collected in litter traps were dried and weighed to study the seasonal changes, peaks in mid-August and late September to October suggested a bimodal annual curve. Study of the seasonal changes in the number of emerged and fallen leaves per shoot revealed a third peak about one month before the August peak, showing a trimodal annual curve. First and second leaves had a longevity of about 40 and 50–60 days, respectively. The longevity increased until the fifth leaf. With the sixth and following leaves, longevity decreased. Leaf size increased with leaf rank, with the first leaf being the smallest. The first leaf had only about 10% and the second leaf only 20% of the area of the fifth leaf. On this basis, the early to mid-July peak in number of fallen leaves was composed of first and second leaves which were smaller and short-lived. The early August and September/October peaks were high in both number and mass of fallen leaves. Compared to reports on Japanese alder of other mountainous districts in Hokkaido, the alder trees of Kushiro Marsh had about the same number of leaves per shoot, but had a season of leaf emergence which was about 6 weeks shorter. In addition, the longevity of the longest-lived fifth leaf was about 30–40 days shorter. The short life span of the leaves could be considered as an adaptive strategy of this species to environmental constraints of its habitat.
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    Time-resolved empirical modelling of seasonal development during phenologically opaque periods (1995)
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    International journal of biometeorology 38 (1995), S. 70-77 
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    ISSN: 1432-1254
    Keywords: Phenology ; Empirical analysis ; Empirical modelling ; Multifactorial
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract A new approach for the analysis of empirical phenological data is presented which supports oligofactorial seasonality modelling. The temporal resolution of this approach is only limited by the temporal aggregation or sampling frequency (1 day, typically, in the case of weather elements) of the available primary data on the relevant environmental factors. The phenological periods of interest may be “phenologically opaque” in the sense that they do not contain any phenologically observable events except their onset and end. In traditional approaches, the available primary data are aggregated over the duration of the respective phenological period (weeks or even months, typically, in plant phenology). The new approach is supported by modern mathematical methods, which allow for data analysis under unfavourable conditions of irregular oligofactorial data design, and could thus also upgrade traditional approaches of phenological data analysis.
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    First approximation to a phenology of the honeybees (Apis mellifera) and flora of Africa (1995)
    Springer
    Oecologia 101 (1995), S. 265-273 
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    ISSN: 1432-1939
    Keywords: Phenology ; Flowering ; Honeybees ; Africa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Peak flowering by the total flora of Africa coincides with or immediately follows peak rainfall. Flowering intensity of the total flora decreases with distance from the equator, but that of the honeybee plant resource base (±2% of total flora) does not. Flowering in the latter is highly synchronous (months 1–5 north of and 9–11 south of the equator). Both total and honeybee flora are completely incongruent with either the biomes or phytochoria of Africa. There is no significant correspondence between honeybee phenology and the total flora but significant correspondence occurs between honeybees and flowering in honeybee plant genera. A logistic regression model reveals that honeybee plant flowering predicts major honeybee colony events with a probability of 0.81 south of the equator and 0.71 for the whole continent. It is postulated that promiscuity in the bee plant genera and honeybees of Africa have contributed to their continental ubiquity.
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    The basis for variation in leaf longevity of plants (1995)
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    Plant ecology 121 (1995), S. 89-100 
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    ISSN: 1573-5052
    Keywords: Deciduous ; Evergreen ; Leaf habit ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Any theory of leaf phenology must predict leaf longevity, leaf habit, leaf expansion and its timing among other variables. These phenological traits may be important keys to understand the response of trees to climatic change. Here I concentrate on and review two of these critical phenological traits, leaf longevity and leaf habit. Theories of leaf longevity were re-evaluated and leaf longevity is concluded to be optimized to maximize plant carbon gain. From this perspective, three points are predicted. Leaf longevity is short when the photosynthetic rate of the leaf is high, when the photosynthetic rate decreases rapidly through time, or when the construction cost of the leaf is small. These predictions are well supported by empirical as well as experimental results on various plant species. The theory, which is extended to seasonal environments, is general and applicable to seasonal as well as aseasonal environments. The theory simulated the bimodal geographic distribution of evergreenness.
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    Maintenance of forest species diversity and latitudinal gradient (1995)
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    Plant ecology 121 (1995), S. 127-134 
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    ISSN: 1573-5052
    Keywords: Biodiversity ; Lottery model ; Phenology ; Synchronization of regeneration ; Tropical rain forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The species diversity of trees maintained in tropical rain forests is much higher than in temperate, boreal, or seasonally dry tropical forests. Many hypotheses have been proposed for higher diversity in tropical rain forests, including: (i) higher specialization of resource use, (ii) different mode of disturbance, (iii) smaller opportunity for competition on oligotrophic soil, (iv) higher productivity, (v) more active specific herbivores and pathogens, (vi) evolutionary/ecological history. In this paper we report mathematical models for tree-by-tree replacement. First the analysis of random drift model shows that the effect of gap size to species diversity is not very strong. Second we study phenological segregation model, which has the following assumptions: Basic mechanism for many species to coexist in the community is assumed given by the storage effect of lottery model, as species differ in seasonality in peak fruit production and in the subsequent period of high regeneration ability. Gaps formed during unfavorable season accumulate and become available for regeneration in the beginning of the growing season. The resulting synchronization of regeneration opportunity jeopardizes the coexistence of many similar species in seasonal environments. Analysis of a mathematical model shows: (1) the existence of unfavorable season can greatly reduce the diversity of coexisting species. (2) Diversity in the equilibrium community can be high when niche width of each species is broad and resource use is strongly overlapped. (3) Equilibrium community may include several distinct groups of species differing in phenology of regeneration. Effect of unequal niche width and frequency dependent regeneration are also examined.
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    A national survey of airborne pollen and grass flowering in New Zealand, with implications for respiratory disorder (1995)
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    Aerobiologia 11 (1995), S. 239-252 
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    ISSN: 1573-3025
    Keywords: Aerobiology ; Pollen allergy ; Grasses ; New Zealand ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Airborne pollen and spore levels were monitored at seven sites in New Zealand using the Intermittent Cycling Rotorod sampler during the summer of 1988/1989. Grasses formed the major component of atmospheric pollen levels during spring and summer at every locality. Peak levels of grass and total pollen occurred during December or late November, with a slight latitudinal lag apparent at the more southern sites. Highest levels were recorded at the smaller rural centres of Gore and Kaikohe and the lowest at the larger urban centres of Auckland, Christchurch and Wellington. We make a first approximation of the likely risk to hayfever and allergic asthma patients at each of the seven centres. For example, significantly higher grass pollen levels were experienced at Kaikohe on 44% and 65% of days during November and December, compared with just 15% and 8% at Auckland. By recording the flowering seasons of the principal allergenic grass species at each locality, we determined the potentially allergenic grasses contributing to peak pollen levels, the most ubiquitous being tall fescue (Festuca arundinacea Schreb.), ryegrass (Lolium perenne L.,L. multiflorum Lam.), cocksfoot (Dactylis glomerata L.), Yorkshire fog (Holcus lanatus L.) and sweet vernal (Anthoxanthum odoratum L.).
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    Monitoring global change with phenology: The case of the spring green wave (1994)
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    International journal of biometeorology 38 (1994), S. 18-22 
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    ISSN: 1432-1254
    Keywords: Phenology ; Green wave ; Global change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract The centuries-old practice of recording plant and animal events that take place at specific times each year (phenology) should play an important role in monitoring mid-latitude global changes. At least three problems related to the detection of biosphere changes could be investigated using this information. Firstly, the technique can be generalized from the local to global scale. Secondly, an integrated approach could be developed to represent biome diversity effectively. Lastly, physical mechanisms responsible for the events can be deduced in order to incorporate the phenological information into global-scale models, and detect changes in related environmental factors. With these goals in mind, regional phenological data collection networks were initiated in eastern North America during the early 1960s, using cloned lilacs and several species of honeysuckle. This paper reviews research projects which address the problems outlined above, using first leaf data (associated with spring green-up or “green wave” in mid-latitudes) gathered from these networks. The results of such studies in North America have demonstrated the potential of phenology as an efficient monitor of global change throughout mid-latitude regions. Future research efforts will concentrate on the development of a coordinated strategy to link phenological information from satellites, indicator plants (such as the lilac), and representative species from each biome.
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    Asphodelus aestivus, an example of synchronization with the climate periodicity (1994)
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    International journal of biometeorology 38 (1994), S. 28-32 
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    ISSN: 1432-1254
    Keywords: Mediterranean ecosystems ; Climatic periodicity ; Geophyte ; Phenology ; Biomass oscillations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract The phenology ofAsphodelus aestivus Brot. is described by means of a phenological model which has been formulated to fit skewed phenological data. Based on the model parameters the timing of different phenophases of biomass accumulation were determined. The biomass oscillations of leaves, inflorescence stalks and tubers were found to be synchronized with the predictable seasonal climatic changes. In addition, the plant seems to respond to minor random climatic variations. The emergence of leaves and inflorescence stalks depends on stored material in the tubers while leaf and inflorescence stalk elongation as well as flowering depends on current production. The storage part of the tubers seems to be a regulating structure, which is responsible for the synchronization ofA. aestivus productivity with the seasonality of the Mediterranean climate.A. aestivus is considered to be a Competitor Ruderal and Stress tolerant (C-R-S) strategist which may explain the wide distribution of this plant over the Mediterranean Basin.
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    Effects of plant size and water relations on gas exchange and growth of the desert shrub Larrea tridentata (1994)
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    Oecologia 97 (1994), S. 171-178 
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    ISSN: 1432-1939
    Keywords: Gas-exchange ; Larrea tridentata ; Phenology ; Stomatal conductance ; Water relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Larrea tridentata is a xerophytic evergreen shrub, dominant in the arid regions of the southwestern United States. We examined relationships between gasexchange characteristics, plant and soil water relations, and growth responses of large versus small shrubs of L. tridentata over the course of a summer growing season in the Chihuahuan Desert of southern New Mexico, USA. The soil wetting front did not reach 0.6 m, and soils at depths of 0.6 and 0.9 m remained dry throughout the summer, suggesting that L. tridentata extracts water largely from soil near the surface. Surface soil layers (〈0.3 m) were drier under large plants, but predawn xylem water potentials were similar for both plant sizes suggesting some access to deeper soil moisture reserves by large plants. Stem elongation rates were about 40% less in large, reproductively active shrubs than in small, reproductively inactive shrubs. Maximal net photosynthetic rates (Pmax) occurred in early summer (21.3 μ mol m-2 s-1), when pre-dawn xylem water potential (XWP) reached ca. -1 MPa. Although both shrub sizes exhibited similar responses to environmental factors, small shrubs recovered faster from short-term drought, when pre-dawn XWP reached about -4.5 MPa and Pmax decreased to only ca. 20% of unstressed levels. Gas exchange measurements yielded a strong relationship between stomatal conductance and photosynthesis, and the relationship between leaf-to-air vapor pressure deficit and stomatal conductance was found to be influenced by pre-dawn XWP. Our results indicate that stomatal responses to water stress and vapor pressure deficit are important in determining rates of carbon gain and water loss in L. tridentata.
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    Patch dynamics ofGlaucopsyche lygdamus (Lycaenidae): correlations between butterfly density and host species diversity (1994)
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    Oecologia 99 (1994), S. 337-342 
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    ISSN: 1432-1939
    Keywords: Diversity ; Host range ; Lycaenidae ; Phenology ; Population persistence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Glaucopsyche lygdamus egg densities were surveyed over a 2000-m section of Gold Creek and at 30 different isolated patches in the Gold Basin drainage in Colorado. Host plant numbers and diversity were quantified, as well as other variables potentially influencing butterfly population size, such as patch size and isolation. Egg densities correlated significantly only with measures of host species diversity. Patches consisting of a single host species, no matter how large, did not support high butterfly densities, but patches of multiple, equitably distributed host species did. The most likely explantation, in light of oviposition preference and larval performance data accumulated for this butterfly species, is that host species diversity is necessary for the persistence ofG. lygdamus populations, because alternative host species buffer population losses during poor or unusual years. The dependence of both ovipositing butterflies and developing larvae on the ephemeral, young, host plant flowers make the butterfly especially vulnerable to year-to-year variation in host plant availability and quality.
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    Patterns of reproduction and habitat use in an assemblage of Neotropical hylid frogs (1994)
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    Oecologia 98 (1994), S. 291-302 
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    ISSN: 1432-1939
    Keywords: Phenology ; Neotropics ; Hylids ; Reproduction ; Seasonality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We censused pond-breeding hylid frogs in northeastern Costa Rica weekly for 15 months to deseribe patterns of reproduction, habitat use, and to establish baseline data on relative abundance for members of the assemblage. Reproduction in the Costa Rican assemblage was seasonal and occurred only during wet months. Some species called, but none reproduced, during the dry season. Three species (Agalychnis callidryas, Hyla ebraccata, and Scinax elaeochroa) accounted for more than 75% of the observations made during the study. The species overlapped broadly in time and space, but differed in substrate use and phenology. Two species of leaf-breeding frogs (A. callidryas and A. saltator) used perches that were significantly higher than those used by the other species. Some phenological differences were associated with different mating strategies. Explosive breeders (Scinax elaeochroa and Smilisca baudinii) were most common early in the wet seasons. Prolonged breeders (A. callidryas and H. ebraccata) were the most persistent members of this assemblage. Predation affects early and late life history stages of these hylids. Predation on arboreal egg masses by two snake species was observed. Ctenid spiders preyed on recently metamorphosed frogs and small adults. Our weekly samples were pooled into 21-day periods so that we could compare our results with those obtained for two communities of breeding anurans from South America. The patterns observed in the Costa Rican assemblage differed from those reported for South American pond-breeding frogs, but in all three assemblages reproduction was associated with wet periods.
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    Phenological and growth patterns of the Mediterranean oak Quercus suber L. (1994)
    Springer
    Trees 9 (1994), S. 41-46 
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    ISSN: 1432-2285
    Keywords: Phenology ; Growth ; Specific leaf weight ; Trees ; Quercus suber L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The phenology of Quercus suber L., a dominant species of the montados in the Iberian Peninsula, was studied for 2 years in southwest Portugal. The seasonal progression of phenological events was analyzed in seven trees. Selected branches were examined monthly for shoot elongation, leaf number, branching, flowering, and fruiting. Radial stem growth and specific leaf weight were also studied. Active growth was observed from early spring to early summer. Reserves accumulated during winter and high photosynthetic activity in early spring apparently supported this strong development. The growth flush started with stem radial increment, which seemed to be impaired by spring rainfall. Male inflorescence production was the next phenological event. Old leaves were shed during new twig and leaf emergence. Shoot elongation and the number of new leaves produced were well correlated with the previous-year shoot's length, and were not clearly related to climatic factors. Radial growth resumed in autumn at a lower rate than in the previous spring, a possible consequence of a reserve depletion due to lower photosynthetic production in summer and investment on fruit maturation, which was complete by late autumn. Premature and excessive new leaf production were apparently subjected to self-pruning strategies related to the development of each tree's crown. Younger cork-oaks produced shorter and fewer shoots per module, and more sclerophyllous leaves than the older ones. A high intra-specific variability was observed in all the results.
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    Morphometric analysis of the genusHemerocallis L. (Liliaceae) in Korea (1994)
    Springer
    Journal of plant research 107 (1994), S. 165-175 
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    ISSN: 1618-0860
    Keywords: Distribution patterns ; Habitats ; Hemerocallis ; KoreanHemerocallis ; Morphometric analysis ; Phenology ; Population studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To better understand the patterns of variability and distributions ofHemerocallis in Korea, 53 locations were visited and measurements of 19 morphological and phenological characters were taken on plants directly from their natural habitats. For morphometric analysis, 10 plants from each of 34 populations and five herbarium specimens ofH. middendorffii were used and the data from 12 quantitative characters was analyzed using univariate analysis. Except the littoral populations of Cheju, Hong, Taehuksan, and Sohuksan Islands (H. hongdoensis M. Chung & S. Kang), three peninsular KoreanHemerocallis species can be recognized mainly in South Korea:H. hakuunensis Nakai (=H. micrantha Nakai, growing on southern, central, and northwestern Korea);H. thunbergii Baker (=H. coreana Nakai, found on southeastern and central Korea); andH. middendorffii Tr. et Mey. (central and northeastern Korea). Morphological and phenological features contributing to recognition of the three groups were; color of perianth, shape of roots, shape of inflorescence, flowering time, odor, length of inflorescence, width of the lowest bracts, length of perianth tube enclosing a ovary, width of the inner perianth lobes. Natural hybridization seems to be rare in KoreanHemerocallis. It appears that the KoreanHemerocallis species are relatively well characterized by their distribution patterns, phenology, and habitats compared with the JapaneseHemerocallis species.
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    URL: http://dx.doi.org/10.1007/BF02346013
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    Agaricus Bisporus: An assessment of its carcinogenic potency (1993)
    Springer
    Mycopathologia 124 (1993), S. 73-77 
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    ISSN: 1573-0832
    Keywords: Assessment ; Cancer ; Humans ; Hydrazines ; Mushroom
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract This assessment focuses on the concentrations of some chemicals present in theAgaricus bisporus mushroom, the cancer-inducing doses of these chemicals or mushroom used in the animal experiments, the total amounts of these chemicals or mushroom needed to induce cancer in these mice, and the estimated total amounts of these chemicals or mushroom needed to induce cancer in humans. By adding the estimated amounts of chemicals needed to induce cancer and by comparing it with the amount of raw mushroom needed to induce the same effect, it becomes obvious that we have accounted for less than 2% of the carcinogenic components of theAgaricus bisporus mushroom. Since some unavailable data handicapped this assessment, it should be regarded as tentative and subject to further adjustment.
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    URL: http://dx.doi.org/10.1007/BF01103105
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    Apparent vs. effective mating in an experimental population of Raphanus sativus (1993)
    Springer
    Oecologia 96 (1993), S. 102-107 
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    ISSN: 1432-1939
    Keywords: Male reproductive success ; Plant mating ; Phenology ; Plant reproduction ; Pollen removal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Effective mating in plant populations need not occur during periods of peak pollinator activity and flowering. We measured seasonal and diurnal patterns of pollinator activity, pollen and ovule availability, and seed production in an experimental population of Raphanus sativus to infer the times of reproductively effective mating. On a seasonal scale, we found that most “effective matings”, those resulting in mature seeds, occurred very early in the season, well before the peak of flowering and pollinator activity. At a finer scale, diurnal schedules of flower opening, stigma saturation with pollen, and pollen removal indicated that most effective matings occurred before noon, even though pollinator activity increased later in the day. These patterns may be most common in populations that are not pollen limited, but other ecological factors (e.g. seed predation, resource depletion) could weaken the correspondence between pollination and effective mating.
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    Leaf flushing phenology and herbivory in a tropical dry deciduous forest, southern India (1993)
    Springer
    Oecologia 94 (1993), S. 114-119 
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    ISSN: 1432-1939
    Keywords: Phenology ; Leaf flushing ; Insect herbivory ; Tropical deciduous forests ; Southern India
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Patterns of leaf-flushing phenology of trees in relation to insect herbivore damage were studied at two sites in a seasonal tropical dry forest in Mudumalai, southern India, from April 1988 to August 1990. At both sites the trees began to flush leaves during the dry season, reaching a peak leaf-flushing phase before the onset of rains. Herbivorous insects emerged with the rains and attained a peak biomass during the wet months. Trees that flushed leaves later in the season suffered significantly higher damage by insects compared to those that flushed early or in synchrony during the peak flushing phase. Species whose leaves were endowed with physical defenses such as waxes suffered less damage than those not possessing such defenses. There was a positive association between the abundance of a species and leaf damage levels. These observations indicate that herbivory may have played a major role in moulding leaf flushing phenology in trees of the seasonal tropics.
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    Comparative physiology and demography of three Neotropical forest shrubs: alternative shade-adaptive character syndromes (1993)
    Springer
    Oecologia 96 (1993), S. 526-536 
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    ISSN: 1432-1939
    Keywords: Leaf longevity ; Phenology ; Photosynthetic capacity ; Rubiaceae ; Survivorship
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A suite of functionally-related characters and demography of three species of Neotropical shadeadapted understory shrubs (Psychotria, Rubiaceae) were studied in the field over five years. Plants were growing in large-scale irrigated and control treatments in gaps and shade in old-growth moist forest at Barro Colorado Island, Panama. Irrigation demonstrated that dry-season drought limited stomatal conductance, light saturated photosynthesis, and leaf longevity in all three species. Drought increased mortality of P. furcata. In contrast, irrigation did not affect measures of photosynthetic capacity determined with an oxygen electrode or from photosynthesis-CO2 response curves in the field. Drought stress limited field photosynthesis and leaf and plant survivorship without affecting photosynthetic capacity during late dry season. Leaves grown in high light in naturally occurring treefall gaps had higher photosynthetic capacity, dark respiration and mass per unit area than leaves grown in the shaded understory. P. furcata had the lowest acclimation to high light for all of these characters, and plant mortality was greater in gaps than in shaded understory for this species. The higher photosynthetic capacity of gap-grown leaves was also apparent when photosynthetic capacity was calculated on a leaf mass basis. Acclimation to high light involved repackaging (higher mass per unit leaf area) as well as higher photosynthetic capacity per unit leaf mass in these species. The three species showed two distinct syndromes of functionally-related adaptations to low light. P. limonensis and P. marginata had high leaf longevity (∼3 years), high plant survivorship, low leaf nitrogen content, and high leaf mass per unit area. In contrast, P. furcata had low leaf survivorship (∼1 year), high plant mortality (77–96% in 39 months), low leaf mass per unit area, high leaf nitrogen content, and the highest leaf area to total plant mass; the lowest levels of shelf shading, dark respiration and light compensation; and the highest stem diameter growth rates. This suite of characters may permit higher whole-plant carbon gain and high leaf and population turnover in P. furcata. Growth in deep shade can be accomplished through alternative character syndromes, and leaf longevity may not be correlated with photosynthetic capacity in shade adapted plants.
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    Adult emergence phenology in checkerspot butterflies: the effects of macroclimate, topoclimate, and population history (1993)
    Springer
    Oecologia 96 (1993), S. 261-270 
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    ISSN: 1432-1939
    Keywords: Phenology ; Euphydryas insolation ; Microclimate ; Thermal ecology ; Topography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The prediction of adult emergence times in insect populations can be greatly complicated by microclimatic gradients, especially in circumstances where distributions of juveniles along those gradients vary from year to year. To investigate adult emergence patterns in topographically heterogeneous habitats, we built a model of postdiapause development of the Bay checkerspot butterfly, Euphydryas editha bayensis. The model uses slope-specific insolation as the rate-controlling variable, and accounts for both solar exposure of the habitat and cloud cover. Instar-specific larval mass gains per unit of insolation were determined from mark-recapture experiments. A small correction for daily low temperatures was used to calibrate the model to five years of field data on larval mass. The model predicted mean mass of 90% of larval samples within 4 clear days over a 70–120 day growing season. The magnitude of spatial variation in emergence times across habitat slopes is greater than annual variation in emergence times due to yearly weather conditions. Historical variation (yearly shifts in larval distributions across slopes) is an important determinant of mean population emergence dates. All of these factors need to be considered in understanding adult emergence phenology in this butterfly and in other insects inhabiting heterogeneous thermal environments. Such an understanding can be useful in managing insect populations for both pest control and conservation.
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    Sequential variation in the components of reproductive success in the distylousJasminum fruticans (Oleaceae) (1993)
    Springer
    Oecologia 94 (1993), S. 480-487 
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    ISSN: 1432-1939
    Keywords: Distyly ; Phenology ; Reproductive success ; Jasminum ; Pollination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A 2-year study of three natural populations of the distylousJasminum fruticans showed that mean fruit and seed production were significantly greater in shortstyled plants (thrums) than in long-styled plants (pins). In this study, we investigated the role of four sequential factors which may differentially influence fruit and seed set in the two floral morphs: (1) differences in flowering phenology, (2) a limitation of pollen transfer towards pins, (3) a differential capacity of the two morphs to act through famale and male function and (4) differential fruit abortion in the two morphs. Fruit set was significantly influenced by differences in flowering phenology although there were no differences in flowering time between the two morphs. supplementary pollinations in a natural population significantly increased fruit set and reduced the difference in fruit set between the two morphs in relation to controls, indicating a limitation on pollen transfer which was most severe towards pin stigmas. In reciprocal crosses, seed set was significantly dependent on the paternal and maternal identity of the pin parent. There was no significant variation among thrums for their performance as male or female parent. Furthermore, individual pin plants with relatively high percentage seed set as female parents gave poor seed set as male parents and vice-versa. Whereas fruit removal had no effect on seed number in thrum plants, a greater proportion of viable seeds were produced on pin plants which were left to naturally mature their fruits than on pins which had fruits artificially removed, suggesting the occurrence of selective fruit abortion in pins but not in thrums. The initially greater maternal fitness of thrums due to their greater success as pollen recipients may thus be opposed by increased viable seed set in the pins due to factors acting after the pollination stage. The relative reproductive success of floral morphs in the distylousJ. fruticans is thus differentially influenced by ecological factors occurring at different stages of the reproductive process.
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    A whole-system reconsideration of paradigms about photoperiod and temperature control of crop yield (1993)
    Springer
    Theoretical and applied genetics 86 (1993), S. 17-26 
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    ISSN: 1432-2242
    Keywords: Yield physiology ; Phenology ; Crop adaptation ; Harvest index ; Crop maturity ; Aerial biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Effects by photoperiod gene(s) and daylength on crop yield and its three major physiological components (aerial biomass, harvest index, and days to harvest maturity) are reviewed for bean (Phaseolus vulgaris L.) and peanut (Arachis hypogaea L.). In these plus many other cited crops, photoperiod sensitive gene(s) delay days to flowering and/or days to maturity in non-promotive daylength while simultaneously lowering the harvest index. Thus, for many crops, earlier maturity is associated with higher harvest index, and/or it has been shown that photoperiod gene(s) control partitioning of photosynthate toward reproductive growth versus toward competitive partitioning to continued vegetative growth. Our conclusion is that photoperiod gene control over this partitioning precedes and is causal of the photoperiodgene control over days to flowering and maturity. This implies shifts from commonly accepted paradigms about effects by photoperiod and about breeding for higher yield. These paradigm shifts suggest more efficient ways to breed for cultivar adaption to the specific growing season duration and environment of each geographical site and for higher crop yield.
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    Reproductive biology of twoPrunus species (Rosaceae) in the Northwest Iberian Peninsula (1993)
    Springer
    Plant systematics and evolution 185 (1993), S. 153-165 
    Details
    ISSN: 1615-6110
    Keywords: Rosaceae ; Prunus mahaleb ; P. spinosa ; Phenology ; pollination ; reproductive systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied the reproductive biology ofPrunus spinosa andPrunus mahaleb (Prunoideae, Rosaceae) in the northwest Iberian Peninsula. The two species flowered at the same time (peaking on March 9 and 11, respectively in 1990) but differ significantly in their fruit maturation times. Nectar volume peaked in the early morning in both species, and was ten times greater inP. spinosa than inP. mahaleb. Neither species shows apomixis, nor does fruit-set occur if pollinators are excluded. In both species self-pollination resulted in fewer fruits than open pollination. The principal pollinators belong to theApidae family (79% and 63% of visits toP. spinosa andP. mahaleb, respectively). Results are compared with those for other rosaceous plants with fleshy fruits.
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    Pollination biology and sexual differentiation ofOsyris alba (Santalaceae) in the Mediterranean region (1993)
    Springer
    Plant systematics and evolution 188 (1993), S. 1-16 
    Details
    ISSN: 1615-6110
    Keywords: Santalaceae ; Osyris alba ; Phenology ; dioecy ; floral morphology ; floral mimicry ; pollination biology ; Mediterranean shrublands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Osyris alba L. is a widespread dioecious hemiparasitic shrub of S Europe, N Africa, and SW Asia. Male inflorescences are multiflowered whereas each female inflorescence is reduced to a single flower with persistent enlarged bracts. Pollination is a prerequisite for fruit and seed development and wind is unlikely to be an effective means of pollen spread. In southern Italy pollen is transported by small unspecialized flies and beetles. Both male and female flowers produce an indistinguishable sweet odour. Male flowers are produced in large numbers and over a larger period than the females and provide pollen, nectar, and staminal hairs as rewards for pollinators. The presence and function of staminal hairs with tip cells inOsyris alba has been reported for the first time. Female flowers are rewardless, producing neither mature pollen, nectar nor staminal hairs, but possess three modified yellow indehiscent anthers containing no viable pollen which may provide a strong visual feeding stimulus for pollinators. It is suggested that pollinators are attracted by deceit to female flowers by mimicry of the males and the floral mimicry is, therefore, intraspecific and intersexual. The floral characteristics and flowering phenology of male and female plants are consistent with this kind of mimicry. The female flower possesses a tricarpellary ovary with three ovules of which only one develops. The single seed, containing a small embryo and a large, rich endosperm, is borne in a red fleshy bird-dispersed fruit. The reduction in seed number per flower to one highly nutrient-invested seed, together with a reduction of the multiflowered inflorescence to a solitary flower and the sequential production of ripe fruits over an extended fruiting season, suggest that the female function is markedly resource-limited. It is suggested that, although all the reproductive characteristics present inOsyris alba, as well as hemiparasitism, had probably evolved before the end of the tropical Tertiary, they are of adaptive advantage in the nutrient and water-limited environment of the Mediterranean maquis.
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    Influence of the viscoelastic properties of the respiratory system on the energetically optimum breathing frequency (1993)
    Springer
    Annals of biomedical engineering 21 (1993), S. 489-499 
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    ISSN: 1573-9686
    Keywords: Work of breathing ; Inspiratory pressure-time integral ; Respiratory modeling ; Dogs ; Humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract We hypothesized that the viscoelastic properties of the respiratory system should have significant implications for the energetically optimal frequency of breathing, in view of the fact that these properties cause marked dependencies of overall system resistance and elastance on frequency. To test our hypothesis we simulated two models of canine and human respiratory system mechanics during sinusoidal breathing and calculated the inspiratory work ( $$\dot W$$ ) and pressure-time integral (PTI) per minute under both resting and exercise conditions. The two models were a two-compartment viscoelastic model and a single-compartment model. Requiring minute alveolar ventilation to be fixed, we found that both models predicted almost identical optimum breathing frequencies. The calculated PTI was very insensitive to increases in breathing frequency above the optimal frequencies, while $$\dot W$$ was found to increase slowly with frequency above its optimum. In contrast, both $$\dot W$$ and PTI increased sharply as frequency decreased below their respective optima. A sensitivity analysis showed that the model predictions were very insensitive to the elastance and resistance values chosen to characterize tissue viscoelasticity. We conclude that the $$\dot W$$ criterion for choosing the frequency of breathing is compatible with observations in nature, whereas the optimal frequency predictions of the PTI are rather too high. Both criteria allow for a fairly wide margin of choice in frequency above the optimum values without incurring excessive additional energy expenditure. Furthermore, contrary to our expectations, the viscoelastic properties of the respiratory system tissues do not pose a noticeable problem to the respiratory controller in terms of energy expenditure.
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    Phylogenetic evidence for multiple Alu source genes (1992)
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    Journal of molecular evolution 35 (1992), S. 7-16 
    Details
    ISSN: 1432-1432
    Keywords: Alu source genes ; Humans ; Gorillas ; Retrotransposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A member of the young PV Alu sub-family is detected in chimpanzee DNA showing that the PV subfamily is not specific to human DNA. This particular Alu is absent from the orthologous loci in both human and gorilla DNAs, indicating that PV subfamily members transposed within the chimpanzee lineage following the divergence of chimpanzee from both gorilla and human. These findings and previous reports describing the transpositional activity of other Alu sequences within the human, gorilla, and chimpanzee lineages provide phylogenetic evidence for the existence of multiple Alu source genes. Sequences surrounding this particular Alu resemble known transcriptional control elements associated with RNA polymerase III, suggesting a mechanism by which cis-acting elements might be acquired upon retrotransposition.
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    The evolution of two west African populations (1992)
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    Journal of molecular evolution 34 (1992), S. 336-344 
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    ISSN: 1432-1432
    Keywords: Humans ; Mitochondrial DNA ; Nuclear polymorphisms ; Heteroplasmy ; Genetic differentiation ; Sickle cell ; Rain forest refuges
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The identification of genetically coherent populations is essential for understanding human evolution. Among the culturally uniform ethnic groups of west Africa, there are two geographically distinct populations with high frequencies of sickle-cell hemoglobin (HbS). Although the HbS mutation in each group is found on distinguishable chromosomes 11, these populations have been assumed to be parts of a single population. Analysis of mitochondrial DNA (mtDNA) in these populations demonstrated that the two populations identified by alternative chromosomes 11 bearing HbS have distinct distributions of mitochondrial genotypes, i.e., they are maternally separate. These studies also showed that, contrary to expectation, the mtDNA of some individuals is heteroplasmic. For nuclear loci, a comparison of the frequency of alternative alleles established that these populations are genetically distinct. Both the mitochondrial and nuclear data indicate that these populations have been separate for approximately 50,000 years. Although HbS in the two populations is usually attributed to recent, independent mutations, the duration of the separation and the observed geographic distribution of the population allow for the possibility of an ancient origin of HbS. Assuming an ancient mutation and considering the known biogeography, we suggest that HbS protected selected populations from malaria in rain forest refuges during the most recent ice age.
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    Differentiation of spring emerging and autumn emerging ecotypes in Galium spurium L. var. echinospermon (1992)
    Springer
    Oecologia 89 (1992), S. 42-46 
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    ISSN: 1432-1939
    Keywords: Seed germination differentiation ; Dormancy ; Spring germinator ; Autumn germinator ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ecotypes of Galium spurium L. var. echinospermon with distinct germination phenologies were found to occur in two adjacent plots of a grassland nature reserve with different management histories: a spring-germinating population is present in a winter-burnt plot, and an autumn-germinating type in an unburnt plot. These ecotypes share common flowering and fruiting phenologies, and disperse their seeds in early summer. Markedly contrasting thermal dormancy/germination characteristics were demonstrated for their seeds in systematic laboratory tests performed after several types of seed storage including storage in the field. The primary dormancy of seeds of the spring germinator was removed by moist-chilling or field winter-chilling, while that of the autumn germinator was removed by moist storage at 25°C or field summer temperatures. Biseasonal seedling emergence of the species appears to be due to a local differentiation of distinct ecotypes.
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    Sources of variation in rapidly inducible responses to leaf damage in the mountain birch-insect herbivore system (1992)
    Springer
    Oecologia 91 (1992), S. 318-331 
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    ISSN: 1432-1939
    Keywords: Betula pubescens ; Epirrita autumnata ; Rapidly inducible responses ; Phenology ; Conditioning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Studies on rapidly inducible resistance in trees against insect herbivores show substantial variation in the strength of responses. Here we report the results of a study which examined causes of this variation. We bioassayed the quality of leaves of two developmental phases (young vs. mature) of the mountain birch Betula pubescens ssp. tortuosa by measuring the growth of two instars of Epirrita autumnata larvae. We used only short shoot leaves from trees of a natural stand, uniform in size and age. Damage was caused by larvae and artificial tearing of leaf lamina, varying the scale and time. We separated seasonal changes in plants from instar-dependent effects of the animals by testing experimental larvae in two subsequent growth trials. We found that only larval-made damage induced responses in leaves that made the leaves significantly poorer quality for the test larvae. Artificial damage induced only weak responses, and artificial canopy-wide damage even caused slight improvement of leaf quality. Cumulative leaf damage did not strengthen birch responses. Leaves that were in the expansion phase responded to damage while fully-expanded, mature leaves showed no response. The pattern of responses indicated that there might be physiological constraints: small-scale damage induced resistance against the larvae but largescale damage did not. Prevalent weather conditions might have modified these responses. Larvae of two instars and sexes, of low- and high-density populations responded to leaf damage similarly. However, prior experience of larvae with the host plant may have affected subsequent larval performance. Variation in rapidly inducible responses in birches was caused by plant characters rather than by test animals.
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    Drought acclimation among tropical forest shrubs (Psychotria, Rubiaceae) (1992)
    Springer
    Oecologia 89 (1992), S. 457-463 
    Details
    ISSN: 1432-1939
    Keywords: Dry season ; Irrigation ; Osmotic adjustment ; Phenology ; Pressure-volume curves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mechanisms of dry-season drought resistance were evaluated for five evergreen shrubs (Psychotria, Rubiaceae) which occur syntopically in tropical moist forest in central Panama. Rooting depths, leaf conductance, tissue osmotic potentials and elasticity, and the timing of leaf production were evaluated. From wet to dry season, tissue osmotic potentials declined and moduli of elasticity increased in four and five species, respectively. Irrigation only affected osmotic adjustment by P. furcata. The other seasonal changes in leaf tissue properties represented ontogenetic change. Nevertheless, they made an important contribution to dry-season turgor maintenance. Small between-year differences in dry season rainfall had large effects on plant water status. In 1986, 51 mm of rain fell between 1 January and 31 March, and pre-dawn turgor potentials averaged 〈0.1 MPa for all five Psychotria species in March (Wright 1991). In 1989, 111 mm of rain fell in the same period, pre-dawn turgor potentials averaged from 0.75 to 1.0 MPa for three of the species in April, and only P. chagrensis lost turgor. The relation between leaf production and drought differed among species. P. limonensis was buffered against drought by the lowest dry-season conductances and the deepest roots (averaging 244% deeper than its congeners) and was the only species to produce large numbers of leaves in the dry season. P. chagrensis was most susceptible to drought, and leaf production ceased as turgor loss developed. For the other species, water stress during severe dry seasons may select against dry-season leaf production.
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    Litter yield in shrubs of larrea in the andean piedmont of Mendoza, Argentina (1992)
    Springer
    Plant ecology 101 (1992), S. 21-33 
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    ISSN: 1573-5052
    Keywords: Litter ; Phenology ; Rainfall ; Statistic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung In den Larrea divaricata ssp. divaricata und L. cuneifolia Gebüschen des mendoziner Andenvorlandes (1500 m und 1130 m Meereshöhe) wurde die Streuproduktion untersucht. Die Streu wurde getrennt nach Strauchschit, Krauchschit und nacktem Boden in Fallen gesammelt, die stichprobenartig in den Beständen verteilt waren. Ein Jahr lang wurde in jedem Bestand der monatliche Streuanfall ermittelt, wobei die Bläter und Früchte von Larrea von den Stipa-Früchten zwecks Berechnung der relativen Mengen-, grasartige und nicht grasartige, getrennt wurden. Streu und Boden der Bestän wurden bromatologisch analysiert und die Stockstoff, Kalk und Phosphorgehalte bestimmt Derjärliche Nährstoffeintrag wurde schichtweise und als Gesamtmenge berechnet. Das Larrea cuneifolia Gebüsch erzeuchte järlich 4,71 T/ha und das L. divaricata 2,20 T/ha Streu. Diese enthielt 78,66 kg/ha N, 4,24 kg/ha P und 94,20 T/ha Ca im L. cuneifolia-und 31,14 kg/ha N, 1,82 kg/ha P, 34,17 kg/ha Ca im L. divaricata-Gebüsch.
    Notes: Abstract The production of litter was measured for the piedmont communities of Larrea divaricata ssp. dicaricata (1500 m asl) and L. cuneifolia (1130 m asl) near Mendoza, Argentina. Litter was collected in traps randomly distributed in each stand: herbaceous, shrubby and uncovered soil. The monthly average weight of litter was recorded in each stand during one year and discontineously during other two years more. The material was classified as: leaves and fruits of Larrea sp., fruits of Stipa sp. (by its relative abundance), gramineous and non gramineous material. The litter and the soil in each sample were bromatologically analyzed and the N, Ca and P levels also determined. The annual contribution of nutrients was calculated totally and layer by layer. The L. cuneifolia and the L. divaricata thickets produce 4,71 t.ha-1 year-2 and 2,02 t.ha-1.year-2 of litter respectively, that mean 78,66 kg/ha of N, 4,24 kg/ha of P and 94,2 kg/ha of Ca in the first thicket and 31,14 kg/ha of N, 1,82 kg/ha of P and 34,17 kg/ha of Ca in the second one; in one year of study.
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    URL: http://dx.doi.org/10.1007/BF00031912
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    Ecology of vegetative regeneration after coppicing in macchia stands in central Italy (1992)
    Springer
    Plant ecology 99-100 (1992), S. 331-343 
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    ISSN: 1573-5052
    Keywords: Growth pattern ; Quercus ilex L. ; Mediterranean-type ecosystems ; Phenology ; Prolepsis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Vegetative regeneration after coppicing of Quercus ilex, Phillyrea latifolia, and Fraxinus ornus in two macchia stands in the Maremma Nature Park (Grosseto, Italy) has been studied. Observations during the first three years after the cut showed that horizontal space occupation by shoots is rapid (95% of the available space being reoccupied within 3 yrs.) and stool mortality very low. We observed differences among species in resprouting, growth pattern and shoot differentiation. Q. ilex and P. latifolia had a longer budburst period than F. ornus. There were no considerable differences in height growth among the three species in the first year. During the second and third years the height increments decreased. F. ornus average height increments were higher than those of Q. ilex and P. latifolia. These two species produced proleptic flushes from the first year on, while F. ornus only showed spring flush. The examination of proleptic shoots and of summer and autumn rainfall seem to show that the latter control Q. ilex growth and shoot differentiation more than that of other species. Differentiation among shoots of the same stool occurs from the first year onwards and the initial vigour differences amongst shoots remain during the following years. Resprouting, space occupation and shoot differentiation have been discussed in relation to rainfall and temperature. The high stool survival and the strong link between stool vigour parameters before and after coppicing confirm a certain stability in successional dynamics following a single coppicing event.
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    URL: http://dx.doi.org/10.1007/BF00118240
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    An analysis of codon usage in mammals: Selection or mutation bias? (1991)
    Springer
    Journal of molecular evolution 33 (1991), S. 442-449 
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    ISSN: 1432-1432
    Keywords: Humans ; Mouse ; Rat ; Codon usage ; Mutation bias ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A new statistical test has been developed to detect selection on silent sites. This test compares the codon usage within a gene and thus does not require knowledge of which genes are under the greatest selection, that there exist common trends in codon usage across genes, or that genes have the same mutation pattern. It also controls for mutational biases that might be introduced by the adjacent bases. The test was applied to 62 mammalian sequences, the significant codon usage biases were detected in all three species examined (humans, rats, and mice). However, these biases appear not to be the consequence of selection, but of the first base pair in the codon influencing the mutation pattern at the third position.
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    URL: http://dx.doi.org/10.1007/BF02103136
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    Dormancy in peach (Prunus persica L.) flower buds (1991)
    Springer
    Trees 5 (1991), S. 244-246 
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    ISSN: 1432-2285
    Keywords: Peach ; Floral buds ; Vegetative buds ; Morphology ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Peach buds (floral and vegetative) were periodically collected from midsummer until the spring flowering and sprouted under continuous light, 100% relative humidity and 20–25°C. Treatments with 200 ppm gibberellin A3 (GA3) or chilling (2–4°C for 30 days before planting) were applied. Vegetative buds showed well-defined phenological stages: pre-dormancy, “true dormancy”, and end of dormancy. Both GA3 and chilling treatments shortened the sprouting times of vegetative dormant buds close to those in predormancy. Isolated floral buds were irresponsive under all conditions and did not sprout even with the GA3 or chilling treatments. In a comparative study with buds immediately after collection anatomical analysis demonstrated that vegetative buds were almost completely developed by midsummer/early automn and remained in a resting state until the end of winter. Floral buds developed continuously over the same period. Both types of verticils began to differentiate in midsummer. Sepals and petals developed mainly in late summer, androecious floral parts developed throughout the resting period, while gynoecious floral parts showed differentiation in late winter. The flower was completely formed a few days prior to blossoming. Thus, in isolated peach buds fertile verticils are not sufficiently developed during the resting time to allow sprouting.
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    URL: http://dx.doi.org/10.1007/BF00227532
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    Modelling relation of first shoot emergence in various tree species to meteorological parameters in Slovenia (1991)
    Springer
    International journal of biometeorology 34 (1991), S. 221-225 
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    ISSN: 1432-1254
    Keywords: Phenology ; Birch ; Beech ; Oak ; Spruce
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract The relation of first shoot emergence in various tree species (birch, beech, oak and spruce) to meteorological parameters was studied on the basis of phenological and meteorological observations at five locations in Slovenia during 1967–1986. A physical model was developed using tree branch temperature obtained by the energy balance equation. The gained linear dependence of first shoot emergence on effective tree branch temperature was compared with the results obtained by multiple regression analysis among first shoot emergence, effective temperature, global radiation, wind velocity and precipitation. A new method was developed to define the proper biological temperature threshold which was used for effective temperature calculations. Results of the physical model and of the multiple regression analysis are statistically significant and give similar correlations between first shoot emergence and meteorological parameters.
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    URL: http://dx.doi.org/10.1007/BF01041832
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    Spring staging in Brent Geese Branta bernicla: feeding constraints and the impact of diet on the accumulation of body reserves (1991)
    Springer
    Oecologia 87 (1991), S. 19-28 
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    ISSN: 1432-1939
    Keywords: Branta bernicla ; Diet ; Food depletion ; Competition ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The diet composition of Brent Geese Branta bernicla on a salt-marsh was quantified. Puccinellia maritima was the principal food species, while Plantago maritima and Triglochin maritima were less commonly taken. Festuca rubra only acted as a substitute for Puccinellia when production of the latter species dropped. The metabolizable energy of the food plants ranged from 5 to 11 kJ·g−1. By assessing the ingestion rates of geese feeding on different food species, the net intake rate could be derived. Plantago and Triglochin appeared to be the most profitable plants to eat. The proportion of these species in the diet was restricted by (1) the capacity of the alimentary tract, since high intake rates combined with high water contents of the food plants easily led to overfill; and (2) the limited distribution of these plants, in combination with their rapid depletion by grazing geese. These latter factors led to an unequal allocation among individual geese. Most Plantago and Triglochin was obtained by dominant pairs within the flocks. The high quality of Puccinellia allowed geese to gain mass in spring, but the metabolizable energy of this plant species declined during the staging period, and Plantago and Triglochin increased in importance in supplying the geese with components with which to build their body reserves. The timing of the onset of spring growth of the various food species differed between years, and plant phenology was shown to have a profound effect on the final body reserves of the geese.
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    URL: http://dx.doi.org/10.1007/BF00323775
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    Phenological variation in fruit characteristics in vertebrate-dispersed plants (1991)
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    Oecologia 86 (1991), S. 463-470 
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    ISSN: 1432-1939
    Keywords: Fleshy fruits ; Flowering ; Phenology ; Vertebrate dispersal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We investigated inter-specific variation in fruit characteristics — fruit size, seed number per fruit, seed weight, nutritional content, fruit persistence, and fruit synchronization — in relation to flowering and fruiting phenology in 34 species of fleshy fruited plants. Except for aspects of fruit synchrony and persistence, the results in general were inconsistent with previous suggestions about adaptive variation in phenologically related fruit traits. The main results were as follows: (1) Late flowering, late fruiting, lengthy development time from flower to fruit, and highly persistent fruits constitute a complex of correlated characteristics among the species. (2) Synchronization of fruiting within individuals increased from early ripening fruits to late ripening fruits. Fruiting synchrony was more pronounced in species with a small crop size than in species with a large fruit crop, whereas synchrony was not significantly related to flowering synchronization, nor to life form. (3) Nitrogen and carbohydrate content of fruit pulp did not vary in relation to phenology, whereas lipid content decreased from early to late ripening fruits. (4) No seasonal trends were found for variation in seed size or seed number per fruit. (5) Interactions with flowering phenology and developmental constraints are important in phenological fruiting patterns. Temporal variation in start of fruiting was partly (36%) explained by variation in flowering time. Seed weight variation explained 17% of variation in development time from flower to fruit. (6) Despite constraints from flowering and seed development, some adaptive adjustment in fruiting phenology is likely to be allowed for among the investigated species. Such an adaptive variation in fruiting phenology was suggested by intra-generic comparisons of Prunus and Vaccinium species.
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    URL: http://dx.doi.org/10.1007/BF00318311
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    Phenology and photosynthetic activity in sterile and fertile sporophytes of Dryopteris filix-mas (L.) Schott (1991)
    Springer
    Oecologia 86 (1991), S. 159-162 
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    ISSN: 1432-1939
    Keywords: Dryopteris filix-mas ; Fertile and sterile life phases ; Overwintering ; Phenology ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This study describes the phenology of sporophytes of the fern Dryopteris filix-mas in relation to whole plant development. Sterile and fertile potted sporophytes were set out at an exposed site and the seasonal development of the fronds was measured from the commencement of unfolding, through the phase of increasing length, up to discoloration. The physiological activity of the fronds was determined by measuring photosynthetic gas exchange. The fronds of sterile sporophytes unfolded in April, about a week earlier than those of fertile plants, but the colour had already begun to turn in September and their life span was 1–2 months shorter. However, between mid-June and the end of August the sterile sporophytes put out several sets of new fronds: these overwintered without changing color and were still photosynthetically active in the following spring. All types of fronds were fully expanded 1–2 months from the beginning of unfolding and, with a natural supply of CO2, had similar maximum net photosynthetic rates of 8–9 μmol/m2 · s. The decline in photosynthetic performance began before symptoms of senescence were visible and was due to decreased efficiency of the mesophyll. It is concluded that the phenology of D. filix-mas changes with transition from the sterile to the fertile phase. Whereas fertile sporophytes are genuinely summergreen, the sterile sporophytes with their summer fronds remain green throughout the winter and should therefore be termed semi-evergreen. The formation of overwintering summer shoots clearly extends the period of photosynthetic productivity of sterile sporophytes.
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    URL: http://dx.doi.org/10.1007/BF00317526
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    Phenology of tree layer species from the timber line around Kumaun in Central Himalaya, India (1991)
    Springer
    Plant ecology 93 (1991), S. 108-118 
    Details
    ISSN: 1573-5052
    Keywords: Phenology ; Leaf sprouting ; Flowering ; Fruiting ; Leaf drop
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phenology of tree layer species from the timber line of Kumaun in Central Himalaya was carried out during the years 1988-1989. The study indicates the prevalence (66%) of deciduous tree species at timber line vegetation. Growth initiation started in early summer with the rise of temperature. Different phenophases succeeded one another, culminating in leaf drop with the advent of winter. The various phenophases of the tree species at timber line have been discussed and compared with the lower Himalayan forests of Kumaun in India. The present study also supports the idea that the intense fluctuations in environmental conditions determine the onset of different growth activities within the short growing season.
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    URL: http://dx.doi.org/10.1007/BF00033205
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    Components of woody-tissue respiration in young Abies amabilis (Dougl.) Forbes trees (1990)
    Springer
    Trees 4 (1990), S. 88-98 
    Details
    ISSN: 1432-2285
    Keywords: Cambium ; Growth respiration ; Maintenance respiration ; Phenology ; Sapwood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Woody-tissue respiration was measured on five different dates at three to five locations on each of 12 30-year-old Abies amabilis trees. On any given date, temperature-corrected respiration per unit surface area varied 10 to 40-fold between sampling locations. In stems, the two major components of respiration were growth respiration and sapwood maintenance respiration, which were of roughly equal importance during the growing season. There was no evidence of significant cambial maintenance respiration, suggesting that a stand with high bole surface area would not automatically have high respiration. Respiration in branches was much greater than in boles of comparable volume and growth rates, and was significantly correlated with branch height. Branch respiration may include an another significant component in addition to the two seen in bole respiration, possibly associated with carbohydrate mobilization and transport or with CO2 efflux from the transpiration stream.
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    URL: http://dx.doi.org/10.1007/BF00226071
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    Ranking introduced into phenological recording (1990)
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    International journal of biometeorology 34 (1990), S. 60-66 
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    ISSN: 1432-1254
    Keywords: Deciduous trees ; Phenology ; Ranking ; Sweden
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract Generally, phenological recording is based on the recognition of separate phases of development in the organism of interest. In the present study samples were ranked with respect to the stage of bud or leaf development reached at the time of sampling. In April 1982 budding and leaf development of all species of trees and shrubs were recorded over 2 km2 of the northeastern slope of Nävlingeåsen, a horst in southernmost Sweden. During 3 days, of which the first two were consecutive, the author walked a stretch of 12 km, divided into 107 sections. In each of these the first living twig at about 1.5 m above ground was sampled for each species. At the end of the day all twigs from the same species were ranked by two persons independently. The ranks were normalized, and a mean calculated for each section. To reduce the impact of natural variation within a species, and also the influence of microclimate where species cluster, the ranks of the sections were smoothed by weighted moving averages. Using three localities which were investigated twice as fixed points, the ranking lists of separate days were integrated into a single system. A time lag of 4 or 5 days in the onset of spring was established between different localities.
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    URL: http://dx.doi.org/10.1007/BF01045821
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    Phenology of high-altitude plants of Kumaun in Central Himalaya, India (1990)
    Springer
    International journal of biometeorology 34 (1990), S. 122-127 
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    ISSN: 1432-1254
    Keywords: Phenology ; High-altitude plants ; Kumaun ; Central Himalaya
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract The various developmental stages of 184 species of high-altitude plants were studied during 1987 and 1988 in the Pindari glacial moraine area of Kumaun Himalaya in the Central Himalaya. The initiation of growth was synchronised with the beginning of the spring/or summer temperature rise and snowmelt. In this high-altitude zone, the peaks of various phenophases succeeded one after another over about 4 months from early June to October. It is suggested that the plants complete various growth cycles within a very short period of favourable conditions to ensure the survival of their progeny.
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    URL: http://dx.doi.org/10.1007/BF01093457
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    The solar wind and human birth rate: A possible relationship due to magnetic disturbances (1990)
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    International journal of biometeorology 34 (1990), S. 42-48 
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    ISSN: 1432-1254
    Keywords: Briths ; Humans ; Solar wind ; Geomagnetism ; Melatonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract Data obtained from the literature on the annual pattern of human conceptions and plasma melatonin at high latitudes indicated that simple annual rhythms do not exist. Instead, prominent semiannual rhythms are found, with equinoctial troughs and solsticial peaks. A prominent semiannual environmental event is the magnetic disturbance induced by the solar wind. The semiannual magnetic disturbances are worldwide, but most pronounced in the auroral zones where the corpuscular radiation enters the atmosphere. Magnetic indices that predominantly reflect these events were obtained from the literature and correlated with the melatonin and conception data. Significant and inverse correlations were found for Inuit conceptions and the melatonin data. The correlations obtained for 48 contiguous states of the United States indicated that only the extreme northern states exhibited this relationship. These data were compared with a previous correlational study in the United States which established that sunshine was correlated with conceptions in the middle latitude and southern states. An hypothesis of dual control by electromagnetic and magnetic energies is proposed: melatonin is a progonadal hormone in humans controlled by both factors, depending on their relative strength. Other studies are reviewed regarding the possible factors involved in determining the annual pattern of human conceptions. Demographic studies of geographic variation in temporal patterns of conceptions, with particular regard to variations of the magnetic fields on the earth's surface, may provide some insight into the efficacy of these different factors.
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    Floristic composition and phenology of temperate grasslands of Western Himalaya as affected by scraping, fire and heavy grazing (1990)
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    Plant ecology 88 (1990), S. 177-187 
    Details
    ISSN: 1573-5052
    Keywords: Species composition ; Phenology ; Fire ; Scraping ; Heavy grazing ; Biological spectrum ; Density ; Basal Cover ; Contagious
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper reports the analysis of floristic composition and phenology of protected, annually scraped and fired, and heavily grazed grasslands community of Western Himalaya. 2. A total of 19, 20 and 23 species were recorded at protected (S1), annually scraped and fired (S2) and heavily grazed (S3) sites respectively. 3. Domination of therophytic flora as indicated by biological spectrum study, was noted in all the three sites. 4. Density of plants reached a maximum in the rainy season and amounted to be 4300.5, 3439.8 and 3298.0 tillers/m2 on S1, S2 and S3 respectively. 5. Maximum total basal cover was also recorded in the rainy season and amounted to be 769.9, 3390.6 and 2295.7 cm2/m2 on S1, S2 and S3 respectively. 6. Correlation between density and basal cover was positive on all three sites.
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    The phenology and economic potential of Terminalia catappa L. in South-Central Ghana (1990)
    Springer
    Plant ecology 90 (1990), S. 125-131 
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    ISSN: 1573-5052
    Keywords: Economic potential ; Ghana ; Phenology ; Terminalia catappa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Terminalia catappa L. (popularly known as ‘Indian almond’ in Ghana) is a distinctive tree much used in West Africa for shade and as an ornamental plant. By careful observation of the species generally in south-central Ghana, and by a detailed day-by-day analysis for one year of the leaf, fruit and litter production of one typical mature tree, and by chemical analysis of its leaves and fruit, so the phenology and possible economic potential of the species were assessed. In the region of study the main elements in the phenology are two main flushing periods immediately following two main periods of leaf shedding, which occur at the equinoxes, and two major fruit-fall periods which precede the leaf shedding by one month. Fruiting takes place in four main spells, however, and flowering in three. Any or all of the processes may overlap in time. The tree is little used economically, but it is suggested that it might have value not only for shade and ornament but also as a food source and a provider of firewood, building timber, mulch and fertiliser, cooking oil, gum and tannin. Experimental commercial planting of the tree is proposed.
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    Seasonal control over allocation to reproduction in a tussock-forming and a rhizomatous species of Eriophorum in central Alaska (1989)
    Springer
    Oecologia 78 (1989), S. 27-34 
    Details
    ISSN: 1432-1939
    Keywords: Eriophorum vaginatum ; E. scheuchzeri ; Growth ; Flowering ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The evergreen tussock-forming Eriophorum vaginatum revealed consistently earlier (c. 1 moth) phenology and greater biomass per tiller than the summergreen rhizomatous E. scheuchzeri in all four components measured (vegetative and reproductive shoots and stems) under the same climatic regime in central Alaska over one growing season. Greatest allocation to vegetative shoot growth occurred in mid-summer in both species. The tussock growth form of E. vaginatum raised shoot meristems 25–30 cm above the soil surface, where temperatures were warmer, permitting shoot growth to begin earlier in spring and continue longer in autumn than in E. scheuchzeri. Consequently, E. vaginatum was able to allocate reserves to reproductive tillers primarily in autumn and early spring, times when minimal reserves were required for vegetative growth. By contrast, the rhizomatous E. scheuchzeri had a more constrained growing season, and allocation to reproduction coincided with allocation to vegetative growth. For this reason, reserves were drawn down more fully in mid-summer in E. scheuchzeri than in E. vaginatum. The more conservative use of nutrient stores in E. vaginatum may relate to its great longevity, reduced allocation to reproduction (including low seedling recruitment), and relatively stable habitats. The mid-seasonal pulse of allocation to reproduction in E. scheuchzeri appears viable only in relatively fertile disturbed sites, where the soil nutrient supply is sufficient to support simultaneous allocation to vegetative growth and reproduction.
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    Influence of plant phenology on the insect herbivore/bittercress interaction (1989)
    Springer
    Oecologia 79 (1989), S. 111-116 
    Details
    ISSN: 1432-1939
    Keywords: Cardamine cordifolia ; Cruciferae ; Herbivory ; Insect-plant interactions ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We tested the hypothesis that generally higher levels of herbivory on bittercress in sun vs in shade, especially by leaf miners, were related to the earlier phenological development of plants in the sun. Naturally-occurring plants in the sun were taller and had longer leaves than did those in the shade during the first three weeks of the growing season, which corresponded with the timing of adult fly oviposition. We divided individual bittercress plants from the sun into three parts: one part was transplanted into willow shade immediately after snow melt; the other two parts were replanted in the sun and one of these was sprayed with insecticide. The transplant experiment had two primary results. First, bittercress transplanted into the shade suffered significantly higher levels of insect damage than either treatment in the sun. Leaf-mining in the shade also increased and equalled that observed in the sun. These results strongly support the phenology hypothesis; higher damage in the sun is due, at least in part, to the earlier development of plants in sun vs in shade early in the season. Second, the ramets with the greatest damage, e.g. the shade treatment, initiated significantly fewer rosettes than did ramets in the other two treatments. The decrease in vegetative reproduction may have been due to the direct effects of increased insect herbivory on these shade plants. This result is particularly interesting because so little information is available on below-ground, vegetative reproductive response to chronic, above-ground foliage loss to native herbs caused by insect herbivores.
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    URL: http://dx.doi.org/10.1007/BF00378247
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    Timing of reproduction in a prairie legume: seasonal impacts of insects consuming flowers and seeds (1989)
    Springer
    Oecologia 78 (1989), S. 220-230 
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    ISSN: 1432-1939
    Keywords: Flowering time ; Grassland ; Herbivory ; Phenology ; Seed predation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seasonal patterns of insect damage to reproductive tissue of the legume Baptisia australis were studied for three years in native tallgrass priairie. Contrasting seasonal patterns of damage were associated with the major species of insect consumers. The moth Grapholitha tristegana (Olethreutidae) and the weevil Tychius sordidus (Curculionidae), which together infested 80–100% of developing fruits (pods), consistently damaged more seeds on average in early than in late maturing pods. But while late opening flowers were less subject to attack from moths and weevils, they were more subject to attack from chewing insects, particularly blister beetles (Epicauta fabricii, Meloidae), which destroyed 〉80% of all flowers and developing young pods (including moth and weevil larval inhabitants). The blister beetles arrived late in the flowering season and fed particularly on young reproductive tissue, allowing larger, older pods that had developed from early opening flowers to escape destruction. The relative abundances and impacts of blister beetles, moths, and weevils varied from year to year. Adding to the uncertainty of reproductive success of the host plant were the large and variable amounts of damage to immature buds inflicted by insects (including the blister beetles and weevil adults) and late killing frosts. Thus, timing of flowering is critical to success in seed production for B. australis. The heavy impacts of insects and weather can result in a very narrow window in time (which shifts from year to year) during which B. australis can flower with any success. The opposing pressures exerted by insects and weather on floral reproductive success may act in concert with other features of the plant's biology to foster the maintenance of considerable diversity in flowering times among individuals in local populations of B. australis.
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    URL: http://dx.doi.org/10.1007/BF00377159
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    On testing temporal niche differentiation in carabid beetles (1989)
    Springer
    Oecologia 81 (1989), S. 89-96 
    Details
    ISSN: 1432-1939
    Keywords: Niche differentiation ; competition ; Statistical inference ; Phenology ; Carabid beetles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary It is first shown that den Boer's (1985) claims that competition should be rejected as a factor explaining community structure are not warranted by his tests on temporal niche differentiation in carabid beetles. The power of these tests is so low that they are unlikely to detect even the most extreme pattern of niche differentiation. A major factor that affects their power is the procedure of building up an artificial species pool from the local communities to which the test is to be applied. Alternative tests are then presented, and applied to data on annual activity cycles of carabids in three forest biotopes in Belgium. Three factors are shown to strongly affect their outcome: the unit into which the time scale is divided, the criteria used to incorporate constraints, and the set of species selected. Nevertheless, they provide some evidence that there is a growing niche differentiation from the successional to the climax forest, as predicted by competition theory. Other hypotheses, however, could explain the observed pattern.
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    URL: http://dx.doi.org/10.1007/BF00377014
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    Seasonal changes in components of male and female reproductive success in Raphanus sativus L. (Brassicaceae) (1989)
    Springer
    Oecologia 81 (1989), S. 345-353 
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    ISSN: 1432-1939
    Keywords: Phenology ; Raphanus ; Reproductive success ; Expected male fitness ; Flower production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary To document seasonal changes in the reproductive behavior of the perfect-flowered, self-incompatible mustard, Raphanus sativus L., we monitored individual survival, flower and fruit production among 58 individuals in a California population over six census dates (cohorts). Population size declined dramatically and mean individual levels of fruit set changed significantly between cohorts. The frequency distribution of flower and fruit production became increasingly skewed over the first four cohorts. The phenotypic maleness of individuals, a standardized measure of phenotypic gender, oscillated during the reproductive season, peaking in the third and fourth cohorts. We calculated a simple estimate of expected male reproductive success of each plant (the number of fruits sired on conspecifics); this estimate was a function of an individual's flower production and the fruit production of its potential mates in our sampled population. Mean expected male success did not differ significantly among cohorts; expected male success per flower did, however, change significantly among cohorts. Among individuals within each cohort, maternal fruit production and expected male success were both positively correlated with flower production throughout the season. Spearman rank correlation coefficients indicate that the strength of these associations, however, changed during the season. Linear regressions of transformed variables indicated that the shape of several fitness functions also changed over time. In addition, the amount of variation in maternal or expected paternal success explained by flower production declined over the first four cohorts. If typical of wild populations, these temporal changes in these functions suggest that measurements of the intensity of phenotypic selection on flower production will depend on when and how fitness is measured in natural populations.
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    URL: http://dx.doi.org/10.1007/BF00377082
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    The compositional distribution of coding sequences and DNA molecules in humans and murids (1988)
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    Journal of molecular evolution 27 (1988), S. 311-320 
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    ISSN: 1432-1432
    Keywords: Genome composition ; Coding sequences ; Isochores ; Humans ; Murids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The compositional distributions of coding sequences and DNA molecules (in the 50-100-kb range) are remarkably narrower in murids (rat and mouse) compared to humans (as well as to all other mammals explored so far). In murids, both distributions begin at higher and end at lower GC values. A comparison of homologous coding sequences from murids and humans revealed that their different compositional distributions are due to differences in GC levels in all three codon positions, particularly of genes located at both ends of the distribution. In turn, these differences are responsible for differences in both codon usage and amino acids. When GC levels at first+second codon positions and third codon positions, respectively, of murid genes are plotted against corresponding GC levels of homologous human genes, linear relationships (with very high correlation coefficients and slopes of about 0.78 and 0.60, respectively) are found. This indicates a conservation of the order of GC levels in homologous genes from humans and murids. (The same comparison for mouse and rat genes indicates a conservation of GC levels of homologous genes.) A similar linear relationship was observed when plotting GC levels of corresponding DNA fractions (as obtained by density gradient centrifugation in the presence of a sequence-specific ligand) from mouse and human. These findings indicate that orderly compositional changes affecting not only coding sequences but also noncoding sequences took place since the divergence of murids. Such directional fixations of mutations point to the existence of selective pressures affecting the genome as a whole.
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    URL: http://dx.doi.org/10.1007/BF02101193
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    Seasonal patterns of canopy development and carbon gain in nineteen warm desert shrub species (1988)
    Springer
    Oecologia 75 (1988), S. 327-335 
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    ISSN: 1432-1939
    Keywords: Phenology ; Leaf demography ; Carbon balance ; Water stress ; Twig photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Canopy development and photosynthetic rate were measured at monthly intervals over a period of one year in 19 shrub and subshrub species of the Mojave and upper Sonoran Deserts. Thirteen of these species realized a substantial fraction of their total net carbon assimilation via twig photosynthesis. The twig contribution to whole plant yearly carbon gain reached a maximum of 83% in species such as Thamnosma montana, Salizaria mexicana, and Baccharis brachyphylla. This large contribution by twigs was due to both low levels of leaf production and the greater longevity of twig tissues. In some other species, however, leaf and twig organs had similar lifespans. During the year of this study (which had an unusually warm, mild winter), no species showed a pattern of winter deciduousness. The reduction in total photosynthetic area between maximal spring canopy development and mid August summer dormancy ranged from 32 to 94%. Some herbaceous perennial species died back to the ground, but none of the woody shrubs were totally without green canopy area at any time of the year. No species studied were capable of high rates of photosynthesis at low plant water potentials in July and August, but, in those species which maintained a substantial canopy area through the drought period, previously stressed tissues showed substantial recovery after fall rains. Photosynthetic rate was significantly correlated with both plant water potential and tissue nitrogen content over the entire year, but only weakly so. This is due in part to the winter months when plant water potentials and tissue nitrogen contents were high, but photosynthetic rates were often low.
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    URL: http://dx.doi.org/10.1007/BF00376933
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    Outcrossing rates and their relationship to phenology in Triticum dicoccoides (1988)
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    Theoretical and applied genetics 75 (1988), S. 937-944 
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    ISSN: 1432-2242
    Keywords: Outcrossing ; Phenology ; Heterozygosity paradox ; Triticum dicoccoides ; Selfers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Outcrossing rates (t) were estimated in natural and garden populations of wild emmer wheat, Triticum dicoccoides. The estimated t from the natural populations was 0 with the 0.95 upper confidence limit ranging from 0.102 to 0.925 depending on the genetic variation within the population. Outcrossing rates for two genotype classes of this species grown in a common garden were 0.0077 and 0.0018. The difference in Outcrossing rates between the two genotypes is ascribed to phenological differences and hence different available pollen pools. Phenological displacement is discussed as a possible bias in the estimation of outcrossing rates in both predominantly selfing and outcrossing plants.
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    URL: http://dx.doi.org/10.1007/BF00258057
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    Accuracy of visual cover assessments in predieting standing crop and environmental correlation in deciduous forests (1988)
    Springer
    Plant ecology 75 (1988), S. 57-64 
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    ISSN: 1573-5052
    Keywords: Biomass ; Field layer ; Phenology ; Regression analysis ; Riverine forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Five plots with a uniform vegetation were selected subjectively in two riverine forests in Flanders and ground vegetation was sampled on seven occasions. The percentage cover of all species was visually estimated at each occasion using a decimal cover scale. Afterwards standing crop of the moss and herb layer was clipped, sorted, oven-dried and weighed. Linear regressions of standing crop on cover and Spearman rank correlations between the data from the two measures and some environmental variables were used to compare both methods of recording species performance. For the total data matrix the variation explained by the regression equations ranged from 52% for the herb layer to 71% for the moss layer; coefficients of determination for the individual species varied from 30% forUrtica dioica to 90% forRanunculus ficaria. The coincidence in correlation with the environment of biomass and cover data is highly significant (r=0.87). The difference in correlation is usually 〈5%. Seasonal changes in shoot and leaf development and interspecific differences in growth form strongly affected the accuracy of predicting biomass from cover. In general, predictions are best for low growing species (e.g.Eurhynchium praelongum andLamium galeobdolon). Differences in correlation varied around 0.1 and decreased with increasing number of observations. For general purposes, it is suggested that the precision of a harvest method (e.g. standing crop determination) does not compensate for the time profit and the repeatability of the visual cover assessment technique, despite the inconsistencies reported for the latter method.
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    URL: http://dx.doi.org/10.1007/BF00044626
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    Ultrastructure of cells in the cambial region during winter hardening and spring dehardening in Salix dasyclados Wim. grown at two nutrient levels (1987)
    Springer
    Trees 1 (1987), S. 151-163 
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    ISSN: 1432-2285
    Keywords: Cambial activity ; Frost hardiness ; Phenology ; Salix ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The ultrastructure of cells in the cambial region of Salix dasyclados Wim. (clone 78056) was studied during the development of winter hardiness and the onset of cambial activity in spring. Plants were grown at relative growth rates (RG) of 8% and 12% respectively, resulting in different nitrogen content in the stems. Frost hardiness of the plants was estimated by standardized freezing tests. Plants with a higher nitrogen status ceased growth later and started re-growth earlier in spring than plants with lower nitrogen content. Differences in ability to withstand low temperatures during autumn and spring were found between plants grown in the two nutrient treatments. During the development of frost hardiness in the autumn, the number of meristematic cells in the cambial region decreased. The cessation of meristematic activity was accompanied by cell wall thickening and ultrastructural changes in the cells. Frost hardiness increased from the ability to survive -6° C in October to survival of -80° C at the beginning of December. From November to February the cambial region comprised a layer of 2–3 thick-walled cells with conspicuous ultrastructural features. Starch accumulated in plastids in September, decreased during November to March and then increased again in accordance with changes of frost hardiness. Onset of cambial activity began between the end of March and the beginning of April, as shown by increased vacuolization of meristematic cells and mitotic activity. By April, the starch content had increased and lipolysis was observed. Frost hardiness had decreased, and plants with low and high nitrogen content were able to survive -15° C and -10° C, respectively. After budburst, all axillary shoot parts were damaged at temperatures below-3° C.
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    URL: http://dx.doi.org/10.1007/BF00193558
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    Resource distribution and its effect on the mating system of a longhorned beetle, Perarthrus linsleyi (Coleoptera: Cerambycidae) (1987)
    Springer
    Oecologia 73 (1987), S. 317-320 
    Details
    ISSN: 1432-1939
    Keywords: Perarthrus ; Cerambycidae ; Mating system ; Creosote bush ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Adults of Perarthrus linsleyi feed on flowers of creosote bush, Larrea tridentata. Mating also occurs on the flowers and foliage of this plant. This food resource is widely and evenly distributed in space, and is usually abundant. The spatial distribution of the beetles bore no relationship to the spatial distribution of flowers among creosote bushes, nor were female beetles distributed predictably with respect to flower distribution. Males moved widely over the area under study, and moved much more frequently than females. Males actively searched for females, and mounted and began copulation attempts without preliminary courtship. Males did not engage in aggressive defense of females, creosote flowers, or creosote bushes. This species exhibits a scramble competition mating system. The spatial distribution of the food resource is a primary factor in the evolution of the mating system of Perarthrus linsleyi.
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    URL: http://dx.doi.org/10.1007/BF00377525
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    Density-dependent flowering phenology, outcrossing, and reproduction in Impatiens capensis (1987)
    Springer
    Oecologia 72 (1987), S. 341-347 
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    ISSN: 1432-1939
    Keywords: Plant density ; Cleistogamy ; Chasmogamy ; Phenology ; Seed production ; Impatiens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We investigated the effects of plant density on cleistogamous (CL) and chasmogamous (CH) flowering phenology and seed production in a natural Impatiens capensis population, by censusing individually marked plants at experimentally reduced and natural densities. CL flowering was earlier at natural density. This plastic density response may have resulted from a stress-related threshold for CL flowering; slower growing plants at natural density flowered earlier. Although apparently triggered by slow early growth, early CL flowering also involved an additional cost for later growth rate. In contrast, CH flowering was unrelated to relative growth rate, but apparently required a size threshold. Experimental density reduction resulted in earlier CH flowering and a dramatic increase in the percentage of plants producing CH flowers. Individual CL and CH flowering duration and flower production were greater at reduced density. These density-dependent effects caused differences between treatments in the shape and location of population flowering phenology curves. Moreover, the percentage of CH seeds produced per individual was much higher at reduced density. At natural density total seed production per plant was lower and more hierarchical than at lower density, suggesting that dominance and suppression shape jewelweed fitness distributions.
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    URL: http://dx.doi.org/10.1007/BF00377561
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    Rainfall and the interaction of microclimate with larval resources in the population dynamics of checkerspot butterflies (Euphydryas editha) inhabiting serpentine grassland (1987)
    Springer
    Oecologia 71 (1987), S. 161-166 
    Details
    ISSN: 1432-1939
    Keywords: Euphydryas ; Butterfly ; Extinction ; Serpentine ; Microclimate ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The interaction of host plant phenology and microclimatic heterogeneity was examined to determine its role in the population dynamics of checkerspot butterflies, Euphydryas editha, inhabiting serpentine grassland in California's outer Coast Range. Within the 2–3 hectares inhabited by a population of E. editha (Jasper Ridge Area H), microclimatic differences resulting from topographic heterogeneity largely determine the temporal and spatial pattern of senescence of the larval host plants, Plantago erecta and Orthocarpus densiflorus. Survival of larvae from hatching to diapause is extremely low as a result of unpredictable variation in the timing of larval development relative to the timing of host plant senescence, both of which are mediated by microclimatic patterns. During this study, population H declined to near extinction as a result of two consecutive years of record rainfall that apparently disrupted the tenuous temporal relationship between larval development and plant senescence. Retarded development of post-diapause larvae led to a late and extended flight season and delayed egg production; this in turn resulted in massive mortality of pre-diapause larvae due to starvation because host plant senescence occurred before larvae became large enough to enter diapause. Adult population size the following spring was the smallest in 25 years of study. This work emphasizes the importance of microclimatic heterogeneity for understanding population-level processes in small ectothermic animals and underlines the potential importance of such heterogeneity in the establishment of reserves designed to protect such animals
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    URL: http://dx.doi.org/10.1007/BF00377280
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    The ecobiological structure of a mediterranean petrophyte steppe on the southern coast of Crimea (1987)
    Springer
    Plant ecology 71 (1987), S. 21-32 
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    ISSN: 1573-5052
    Keywords: Biological flora ; Biomorphology ; Life form ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ecobiological structure of vegetation syntaxa is determined by summarizing the phenology, chorology, growth forms, and life history attributes of the component species. This approach to vegetation analysis is illustrated by a study of the mediterranean petrophyte steppe (Thymo callieri-Stipetum lithophilae) of the southern coast of Crimea. On the basis of long-term studies, average yearly patterns were determined for such dynamic ecobiological attributes as maximum number of species initiating flowering, maximum flowering, and maximum fruiting. The intensity of biological processes was highest from mid-spring to early summer, but declined sharply in July and August as a consequence of hot, dry climate conditions. Considerable reduction of these processes was noted during winter. Static ecobiological properties of the syntaxon are also summarized. The perspectives of a wider application of the ecobiological approach to the study of world vegetation are discussed.
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    URL: http://dx.doi.org/10.1007/BF00048508
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    Spatial distribution and the performance of individual plants in a natural population of Silene dioica (1986)
    Springer
    Oecologia 70 (1986), S. 121-127 
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    ISSN: 1432-1939
    Keywords: Competition ; Phenology ; Seedling ; Spatial distribution ; Silene dioica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1) A natural population of the perennial herb Silene dioica was mapped at intervals over the course of a year. The ‘space available’ to each plant was estimated by a Thiessen polygon, defined by the position of the plant's neighbours. 2) Germination and recruitment of seedlings appeared to be unrelated to the position of individuals with respect to their neighbours. 3) Various measures of plant growth were strongly correlated with polygon area in some seasons, suggesting that competition was occurring between individuals for spatially distributed resources. Plasticity allowed plants to exploit the available area, regardless of polygon shape or the number of neighbours defining a polygon. 4) In the early spring phase of seedling establishment, growth appeared to be enhanced and seedlings lived longer when they were close to neighbours. In late spring this effect was replaced by the more rapid growth of individuals in the larger polygons, i.e. with more distant neighbours. This sequence of events is consistent with the onset of competition for resources in late spring. 5) These effects were observed despite heterogeneity in the environment and variation in individual response.
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    URL: http://dx.doi.org/10.1007/BF00377120
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    Genetic control of heading date and spikelet number in common wheat (T. aestivum L.) line ‘Noa’ (1986)
    Springer
    Theoretical and applied genetics 72 (1986), S. 105-107 
    Details
    ISSN: 1432-2242
    Keywords: Wheat ; T. aestivum ; Heading date ; Spikelet number ; Phenology ; Day-length insensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The phenology and build-up of spikelet number under 10 h day-length were studied in five wheat lines: the multispikelet line ‘Noa’, the regular line ‘Mara’, the F1 hybrid between them and monosomics 2D of ‘Mara’ and of this hybrid (lacking the 2D chromosome of ‘Mara’). ‘Noa’ had a longer spike development phase, a higher initial number of spikelet primordia and a slower rate of spikelet production than ‘Mara’. The F1 hybrid was similar to ‘Noa’ in its high initial number of spikelets and to ‘Mara’ in its high rate of spikelet production. This hybrid had a shorter spikelet phase than both parents. Deletion of one dose of the ‘Mara’ 2D chromosome from either ‘Mara’ or the F1 hybrid caused a reduction in the rate of spikelet production and an increase in the duration of the spikelet phase. These effects were due to the reduced dosage of the 2D chromosome. However, in the F1 hybrid this deletion also caused an increase in the spike development phase — an indication that ‘Noa’ carries on its 2D chromosome a recessive gene for late heading date which acts on the spike development phase. This gene of ‘Noa’ is independent of the day-length sensitive gene ppd, and is different from ‘Noa’s dominant gene for large initial number of spikelets.
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    URL: http://dx.doi.org/10.1007/BF00261463
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    Successional changes in the morphology and ecological responses of a grazed pasture ecosystem in Central Spain (1986)
    Springer
    Plant ecology 67 (1986), S. 33-44 
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    ISSN: 1573-5052
    Keywords: Ecosystem exploitation ; Grazing ; Herbivore ; Mediterranean pasture ; Phenology ; Phytomass ; Plant morphology ; Succession
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Morphological characteristics related to spatial occupation, reproduction and adaptations to grazing were used to characterize the most frequent species in a therophytic pastureland of Central Spain. Periodic ploughing is a traditional practice in these pastures and allows observation of successional change. In the present study, four neighbouring slopes of differing time since last ploughing were chosen. Species biomass was measured at different times during the annual growing season for two different slope positions. Grazing pressure is an important environmental factor affecting ecosystem organization, the most palatable plants tending to show increasing biomass with succession. In the most mature stages, there is a predominance of species characterized by horizontal occupation of space and sprouting after mowing or grazing. During succession segregation of the different morphological characteristics occurs in slope sectors related to geomorphological dynamics. Similarly, phenological development tends to be later in pastures in the lowest slope zones, due probably to their greater summer soil moisture content.
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    URL: http://dx.doi.org/10.1007/BF00040316
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    Flowering and fruiting phenology in the coastal shrublands of Doñana, south Spain (1986)
    Springer
    Plant ecology 68 (1986), S. 91-98 
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    ISSN: 1573-5052
    Keywords: Coastal dune ; Doñana ; Mediterranean region ; Phenology ; Shrubland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Flowering and fruiting phenological patterns at the individual-, population-, and community level were studied in a southern Spanish scrub community composed of 30 shrub species. Few individuals of any species produced a high number of flowers. Intrapopulation deviation in the peak time of flowering showed a strong and positive skewness. Relative flowering duration, however, displayed a virtually normal distribution. Generally, species flowering in spring have a short flowering time, while species flowering earlier or later in the year show significantly longer flowering periods. Species were in bloom throughout the year, but there was a major peak during spring and two lesser ones in autumn and early summer. Shallow rooting taxa in typically mediterranean genera displayed a strategy of spring flowering and summer fruiting. Summer and autumn flowering occurred among heath-like shrubs of relatively wet places, and forest-associated, vertebrate-dispersed species which commonly have underground storage organs. Species with ripe fruits presented two peaks, the major one during the summer including the majority of taxa with seeds dispersed by non-vertebrate agents. There was a minor fruiting peak in autumn dominated by taxa that rely on vertebrates for dispersal. The complex seasonal patterns observed are interpreted in relation to environmental conditions and physiological constraints on species living in a highly seasonal climate.
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    URL: http://dx.doi.org/10.1007/BF00045059
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    Correlation between aerobiological and phytogeographical investigations in the Florence area (1986)
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    Aerobiologia 2 (1986), S. 2-13 
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    ISSN: 1573-3025
    Keywords: Phenology ; Phytogeography ; Pollens ; Fenologia ; Fitogeografia ; Pollini
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Riassunto Lo scopo della ricerca è stato quello di valutare i risultati della conta pollinica effettuata presso l'U.O. di Allergologia e Immunologia Clinica del Nuovo Osp. S. Giovanni di Dio a Firenze, alla luce dei dati orogeografici, fitogeografici e meteorologici. I più alti valori di conta pollinica sono stati osservati per le Graminaceae, che compaiono precocemente in quantità modeste ma che raggiungono valori molto elevati a partire da Aprile; anche le Oleaceae hanno dato concentrazioni polliniche piuttosto elevate ma per un periodo più breve. La conta pollinica per Compositae ed Urticaceae è risultata più modesta; da segnalare la costante presenza di elevata conta pollinica per Cupressaceae in Febbraio-Marzo. Allo scopo di individuare le fonti prossime e remote della pioggia pollinica, sono state condotte, per aree concentriche, indagini sulla flora allergogena del territorio circostante. Le specie prese in considerazione possono essere ripartite in 7 tipi vegetazionali: boschi xerofili, boschi mesofili, boschi coniferati, parchi e giardini, zone agricole, zone prative naturali, aree marginali e piante infestanti. Una valutazione quantitativa delle singole specie viene desunta dallo studio fitosociologico dei tipi di vegetazione. La rilevazione cartografica di questi tipi permette di individuare le diverse fonti di provenienza del polline. La caratterizzazione stagionale della pioggia pollinica viene meglio definita mediante periodici controlli fenologici sulla flora allergogena esistente, lungo itinerari opportunatamente scelti nelle zone prossime alla località di rilevazione.
    Notes: Summary The aim of our research work was to evaluate the results from our pollen count (p.c.) carried out at the Allergological Centre of Nuovo Osp. San Giovanni di Dio in Florence, in the light of orogeographical, phytogeographical and meteorological data. The highest p.c. was yielded by Graminaceae which appear in small quantities early in the year but increase considereably starting from April. Oleaceae too showed high pollen concentration but over a shorter lenght of time. The p.c. for Compositae and Urticaceae was lower. It should be noted that Cupressaceae yielded constantly high p.c. in February–March. Investigations on the allergenic flora of the surroundings were carried out concentrically in order to find out the closest and the farthest sources of pollen production. The species investigated come under 7 types of vegetation: xerophilous woods, mesophilous woods, conifers woods, parks and gardens, rural areas, meadows, border areas-weeds. A phytosociological study of the types of vegetation has made it possible to evaluate the single species quantitatively. The different sources of pollen production can be spotted by mapping these types of vegetation. The seasonal characterization of pollen production is better defined by means of periodical phenological checking of the existing allergenic flora along carefully planned routes through the areas next to the sampling station.
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  • 99
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    Electronic Resource
    Implementation of periodic acid-thiosemicarbazide-silver proteinate staining for ultrastructural assessment of muscle glycogen utilization during exercise (1985)
    Springer
    Cell & tissue research 242 (1985), S. 229-232 
    Details
    ISSN: 1432-0878
    Keywords: Skeletal muscles ; Ultrastructure ; Exercise ; Glycogen ; Humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Distribution of glycogen particles in semithin and ultrathin sections of biopsy samples from human muscles subjected to either short- or long-term running were investigated using PAS and Periodic Acid-ThioSemiCarbazide-Silver Proteinate (PA-TSC-SP) staining methods. Glycogen particles were predominantly found immediately under the sarcolemma or aligned along the myofibrillar Iband. After long-term exhaustive exercise type-1 fibers with a few or no glycogen particles in the core of the fibers were frequently observed. The subsarcolemmal glycogen stores of these “depleted” type-1 fibers were about three times as large as after exhaustive short-time exercise. Another indication of utilization of subsarcolemmal glycogen stores during anaerobic exercise was that many particles displayed a pale, rudimentary shape. This observation suggests fragmental metabolization of glycogen. Thus, depending on type of exercise and type of fiber differential and sequential glycogen utilization patterns can be observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225582
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  • 100
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    Electronic Resource
    The influence of fire on the phenological behaviour of Mediterranean plant species in Bas-Languedoc (southern France) (1985)
    Springer
    Plant ecology 60 (1985), S. 119-130 
    Details
    ISSN: 1573-5052
    Keywords: Fire effect ; France ; Mediterranean vegetation ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fire is an ancient ecological factor influencing the Mediterranean vegetation of southern France. The study was carried out on three areas to determine the phenological behaviour of plants with regard to fire. First we studied the flowering responses of perennials in relation to the time since fire: in a Quercus coccifera garrigue most species flower during the year following burning. In comparing species by species between burned and unburned areas most species did not show major differences in the phenological stages. However, fire did increase the number of inflorescences of grasses. A phenological synthesis showed that differences at the community level existed for the flowering stages between the burned areas and the unburned control sites during the first and second years following fire. The growth of some woody species was also studied; the elongation and growth of the plants were biggest during the first or second year after fire. The lack of differences in phenological response between burned and unburned plants may be an adaptive trait to fire.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00039927
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