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  • 1
    Electronic Resource
    Electronic Resource
    Ecological trends in lichen photosynthesis (1982)
    Springer
    Oecologia 53 (1982), S. 330-336 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Drawing on data for 42 fruticose and foliose lichen species, four aspects of photosynthetic response have been ex&mined in relation to latitude and climatic variables: 1) the maximal rate of net photosynthesis (Pmax), 2) the tissue temperature at which Pmax occurs (Topt), 3) the photon flux density at which Pmax occurs (PhARsat), and 4) the tissue water status at which Pmax occurs. Tissue water status was measured as either relative water content (RWCopt) or percentage dry weight (DWopt). The Topt decreased significantly with increasing latitude; Topt also increased significantly with increasing July solar radiation, July air temperature, daily hours of bright sunshine, daily solar radiation, annual precipitation, and annual evaporation. Both RWCopt and DWopt increased significantly with annual precipitation. The Topt and RWCopt for a lichen could both be more accurately predicted from multiple regressions on macroclimatic variables describing the lichen's habitat. Both the PhARsat and the Pmax, despite their lack of simple univariate relationships to either latitude or climatic variables, could also be predicted by multiple regression. The limitations on the generality and precision of these ecological trends in lichen photosynthesis are discussed in relation to microclimatic considerations, morphological adaptations, and poikilohydric metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389009
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  • 2
    Electronic Resource
    Electronic Resource
    Responses to moisture stress in male and female plants of Rumex acetosella L. (Polygonaceae) (1982)
    Springer
    Oecologia 53 (1982), S. 305-309 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Male and female plants of Rumex acetosella were grown on a moisture gradient to measure possible differences in the drought tolerance of the sexes. The growth of both sexes declined under water stress but males were significantly more drought tolerant. This could not be explained by greater water use efficiency in the male plants; measured rates of both photosynthesis and leaf conductance did not differ significantly between the sexes. Multiple discriminant analysis showed that the sexes differed at all moisture regimes in their overall patterns of biomass allocation. Males had proportionately greater investment in root and leaf tissue which could explain their growth advantage over females under water stress. Despite essentially equal water use efficiencies, on a per plant basis males, with more leaf and root biomass, could fix more carbon and more rapidly exploit the local water resource than females. Thus the pattern of biomass allocation rather than intrinsic physiological differences appears to explain the greater drought tolerance of male plants of Rumex acetosella.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389005
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  • 3
    Electronic Resource
    Electronic Resource
    The effects of climatic pattern on lichen productivity: Cetraria cucullata (Bell.) Ach. in the arctic tundra of northern Alaska (1981)
    Springer
    Oecologia 50 (1981), S. 210-216 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The climatic control of productivity for two populations of the lichen Cetraria cucullata (Bell.) Ach. growing in the arctic tundra of northern Alaska (70°28′N, 157°23′W) was examined. Respiratory losses of carbon vary with tissue temperature, tissue water content, and time since wetting. Potential net photosynthetic gains of carbon are affected by photon flux density, tissue temperature, and water content. The net CO2 exchange responses of populations growing on ridge tundra and on upland tundra differ and these differences reflect possible adaptation to the normal environmental regimes in the two habitats. Simulation of the lichen's net carbon balance using continuous hourly records of photon flux density, temperature, and water content for the unusually dry period June 28 through July 17, 1977 show that lichen biomass is actually lost during climatic regimes leading to frequent but short periods of lichen metabolic activity. This result is confirmed by the negative relative growth rates measured for C. cucullata over the same monitoring period. This observed loss of biomass may be attributable to depletion of carbon reserves to reactivate dormant metabolism without sufficiently long periods favorable for net photosynthetic activity to replenish the lost reserves. These results illustrate that environmental limits exist on the success of the dormancy strategy characteristic of lichen and moss carbon metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00348040
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  • 4
    Electronic Resource
    Electronic Resource
    Carbon dioxide exchange in Cladina lichens from subarctic and temperate habitats (1978)
    Springer
    Oecologia 32 (1978), S. 225-237 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The survival potential of lichens in a given habitat is determined by the response of CO2 exchange to photosynthetically active radiation (PhAR), thallus temperature, and thallus relative water content (RWC). Therefore morphologically similar lichens from contrasting climatic environments 1) should differ in their CO2 exchange responses, and 2) these differences should reflect adaptations to their climatic regimes. The CO2 exchange responses of a subarctic (55°N, 67°W) Cladina stellaris (Opiz) Brodo population and a temperate (29°N, 82°W) Cladina evansii (Abb.) Hale and W. Culb, population were used to test these two related hypotheses. Infrared gas analysis with lichens collected in September–October 1975 established that the two populations differed in their responses to incident PhAR, thallus temperature, and thallus RWC. Net photosynthesis in C. stellaris had an optimum at a lower temperature and a greater relative photosynthetic capacity at low temperatures than did C. evansii. Cladina evansii maintained net photosynthesis above 35°C thallus temperature; C. stellaris did not. In both species the optimum temperature for net photosynthesis increased with increasing irradiance. The C. stellaris light saturation point was consistently lower than that of C. evansii. Both species had maximal rates of net photosynthesis at 70–80% relative water content. In C. evansii the CO2 exchange rates, expressed as percentages of the maximum rate, declined more rapidly under suboptimal conditions. The absolute CO2 exchange rates of C. evansii were greater than those of C. stellaris. At 20°C and 90–95% RWC, resaturation respiration occurred in both species and continued until 6–7 h after wetting. Contrasts in the temporal patterns of thallus condition at each collection site suggest that not all differences in the two response surfaces reflect climatic adaptation. The two populations appear well adapted to incident PhAR and thallus temperature regimes but the 70–80% RWC optimum for net photosynthesis common to both species is puzzling since their water regimes differ markedly. The overall adaptedness of the CO2 exchange responses in the two species cannot be judged without a comprehensive quantitative analysis of carbon balance under differing climatic regimes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366074
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  • 5
    Electronic Resource
    Electronic Resource
    The sampling characteristics of electivity indices (1982)
    Springer
    Oecologia 52 (1982), S. 22-30 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Electivity indices measure the utilization of food types (r) in relation to their abundance or availability in the environment (p). Foods that constitute a larger proportion of the diet than of the available foods are considered preferred; conversely those proportionately underrepresented in the diet are avoided. A food is eaten at random if its proportion in the diet equals its proportion in the environment. A family of electivity indices stemming from Ivlev's (1961) classic monograph exist and differ only in the particular algorithm used to calculate electivity from r and p. For each available index I graphed the values of electivity as contours for all combinations of r and p. These graphs are compared to illustrate the strengths and weaknesses of each index on the basis of the following criteria: 1) the value of the index when r=p for a food, 2) the symmetry of the electivity value as feeding deviates from random, 3) the possible range of index values, 4) the linearity of changes in electivity over the full range of r and p, 5) the sensitivity of the index to sampling errors, 6) the statistical testability of the electivity, and 7) the stability of the electivity value for a food type that changes relative abundance or occurs in combination with different food types. No one index ideally satisfies all the criteria. The host preferences of gypsy moth, Lymantria dispar, feeding on tree foliage in an undisturbed deciduous forest in southwestern Quebec, Canada were used to compare the available indices: Ivlev's electivity, E; Ivlev's forage ratio, E'; Jacob's modified electivity, D; Jacob's modified forage ratio, log Q; Chesson's alpha; Strauss' linear index, L; and Vanderploeg and Scavia's relativized electivity, E *. The electivity values calculated by each index differ one from another; host trees shown as preferred by one index will frequently appear avoided according to an alternative index. The rank order electivities for the 19 available host trees, however, are remarkably similar for all but Strauss' linear index, L. Populus grandidentata, Quercus rubra, Ostrya virginiana, and Amelanchier were the most preferred host trees in the sampled forest; Prunus serotina, Acer pensylvanicum, A. rubrum, Betula lutea, and Fraxinus americana were most avoided. The use of Vanderploeg and Scavia's E * index is recommended.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349007
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  • 6
    Electronic Resource
    Electronic Resource
    Partitioning the transplant site effect in reciprocal transplant experiments with Impatiens capensis and Impatiens pallida (1986)
    Springer
    Oecologia 70 (1986), S. 149-154 
    Details
    ISSN: 1432-1939
    Keywords: Transplant experiment ; Survivorship ; Fruit production ; Neighbour effects ; Impatiens capensis ; Impatiens pullida ; Balsminaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Modified reciprocal transplant experiments were conducted with the annual plant species Impatients capensis and I. pallida to partition the influence of environment on fitness into two components; that of (1) conspecific neighbours occupying each transplant site, and (2) the abiotic and biotic features of each site exclusive of the conspecific neighbours. In the within-species reciprocal transplant series, differences in survivorship and fruit production by cleistogamous flowers were attributable primarily to the effect of conspecific neighbours. In addition, plants surrounded by neighbours from the site of origin produced significantly more fruit from chasmogamous flowers compared with plants surrounded by neighbours from the alien site. In the between-species reciprocal transplant series, one transplant site was consistently associated with greater survivorship and fruit production regardless of the identity of neighbouring plants. The results suggest that different aspects of the environment in these reciprocal transplant experiments (conspecific neighbours, other species, physical factors) determine fitness in different situations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377125
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  • 7
    Electronic Resource
    Electronic Resource
    Foliage quality changes during canopy development of some northern hardwood trees (1992)
    Springer
    Oecologia 89 (1992), S. 316-323 
    Details
    ISSN: 1432-1939
    Keywords: Host quality ; Leaf phenology ; Synchrony ; Insect-plant interactions ; Lymantria dispar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ephemerality of high quality foliage in spring may act as a defense for trees against early season folivores, but only if the duration of high quality is so short that it is difficult for insects to synchronize their eclosion with the period of high quality foliage that follows budbreak. The rate of change in foliage quality on a day to day basis through the spring was determined for 9 species of hardwood trees in 2–3 years. Measurement of physical and chemical parameters and a bioassay with gypsy moth larvae both showed decreasing quality during the three to five weeks of canopy development in all species. Rates of decline differed among species but the patterns were similar from year to year on a degree-day scale. Growth rates of larvae raised through the first stadium on foliage of differing ages reflected these changes in foliage acceptability. Increasing toughness and declining nitrogen and water contents of leaves were correlated with changes in acceptability to larvae but explained only a small part of the variation in acceptability. The host-seeking period of gypsy moth larvae over-lapped with the availability of highly acceptable foliage of the most preferred host species. Less preferred species had more rapid declines in foliage acceptability, and hence narrower overlaps with the host-seeking period, which may provide defense against use by this generalist forest pest.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317408
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  • 8
    Electronic Resource
    Electronic Resource
    The effects of simulated acid precipitation on photosynthesis in the caribou lichenCladina stellaris (Opiz) Brodo (1982)
    Springer
    Water, air & soil pollution 18 (1982), S. 421-430 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The photosynthetic capacity of the caribou lichen,Cladina stellaris, was impaired when the lichen was wetted by artificial acid precipitation. When wetted by a solution having a pH=4.0 and a sulfate concentration = 10.00 mg l−1, the maximal photosynthetic capacity was lowered 27% from normal levels. Moreover, the lichen which is dormant when dry, took 14% longer after wetting to attain even this reduced rate of photosynthesis. The possibility that lichen growth rates may be reduced by acid precipitation with serious implications for many northern ecosystems is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02419429
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  • 9
    Electronic Resource
    Electronic Resource
    Resistance of the caribou lichen Cladina stellaris (Opiz.) brodo to growth reduction by simulated acidic rain (1987)
    Springer
    Water, air & soil pollution 34 (1987), S. 71-77 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Natural mats of C. stellaris growing in the subarctic lichen woodlands of northern Québec were treated in a randomized complete block design with solutions of simulated rain at pH 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 and 5.6. These solutions were acidified by addition of mixtures of sulfuric and nitric acids to give both 2 : 1 and 6 : 1 μequivalent ratios of SO inf4 sup= : NO inf3 sup− . After two years of acidification there was no significant effect of either pH or SO inf4 sup= : NO inf3 sup− ratio on the growth of C. stellaris, but thallus discoloration was evident below pH 3.5. After three years of acidification marginally significant (p = 0.05) but erratic depression of growth occurred under the 6 : 1 but not the 2 : 1 acidification regime, especially at pH 4.5 or less. Acid precipitation therefore only very gradually impairs the growth of C. stellaris, and the deleterious effects of acidification may be partially offset by nitrogen enrichment when precipitation is relatively rich in nitrate compared to sulfate ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00176868
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  • 10
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    Functional ecology of advance regeneration in relation to light in boreal forests (1999)
    Canadian Science Publishing
    Details
    Publication Date: 1999-06-01
    Description: This paper reviews aspects of the functional ecology of naturally established tree seedlings in the boreal forests of North America with an emphasis on the relationship between light availability and the growth and survival of shade tolerant conifers up to pole size. Shade tolerant conifer species such as firs and spruces tend to have a lower specific leaf mass, photosynthetic rate at saturation, live crown ratio, STAR (shoot silhouette area to total needle surface area ratio), and root to shoot ratio than the shade intolerant pines. The inability of intolerant species such as the pines and aspen to survive in shade appears to be mainly the result of characteristics at the shoot, crown, and whole-tree levels and not at the leaf level. Although firs and spruces frequently coexist in shaded understories, they do not have identical growth patterns and crown architectures. We propose a simple framework based on the maximum height that different tree species can sustain in shade, which may help managers determine the timing of partial or complete harvests. Consideration of these functional aspects of regeneration is important to the understanding of boreal forest dynamics and can be useful to forest managers seeking to develop or assess novel silvicultural systems.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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