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  • 21
    Electronic Resource
    Electronic Resource
    Inter- and intra-generic differences in growth, reproduction, and fitness of nine herbaceous annual species grown in elevated CO2 environments (1995)
    Springer
    Oecologia 104 (1995), S. 454-466 
    Details
    ISSN: 1432-1939
    Keywords: Cassia ; Ipomoea ; Polygonum ; CO2 ; Reproduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In assessing the capacity of plants to adapt to rapidly changing global climate, we must elucidate the impacts of elevated carbon dioxide on reproduction, fitness and evolution. We investigated how elevated CO2 influenced reproduction and growth of plants exhibiting a range of floral morphologies, the implications of shifts in allocation for fitness in these species, and whether related taxa would show similar patterns of response. Three herbaceous, annual species each of the genera Polygonum, Ipomoea, and Cassia were grown under 350 or 700 ppm CO2. Vegetative growth and reproductive output were measured non-destructively throughout the full life span, and vegetative biomass was quantified for a subsample of plants in a harvest at first flowering. Viability and germination studies of seed progeny were conducted to characterize fitness precisely. Early vegetative growth was often enhanced in high-CO2 grown plants of Polygonum and Cassia (but not Ipomoea). However, early vegetative growth was not a strong predictor of subsequent reproduction. Phenology and production of floral buds, flowers, unripe and abscised fruits differed between CO2 treatments, and genera differed in their reproductive and fitness responses to elevated CO2. Polygonum and Cassia species showed accelerated, enhanced reproduction, while Ipomoea species generally declined in reproductive output in elevated CO2. Seed “quality” and fitness (in terms of viability and percentage germination) were not always directly correlated with quantity produced, indicating that output alone may not reliably indicate fitness or evolutionary potential. Species within genera typically responded more consistently to CO2 than unrelated species. Cluster analyses were performed separately on suites of vegetative and reproductive characters. Some species assorted within genera when these reproductive responses were considered, but vegetative responses did not reflect taxonomic affinity in these plants. Congeners may respond similarly in terms of reproductive output under global change, but fitness and prognoses of population persistence and evolutionary performance can be inferred only rarely from examination of vegetative characters alone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00341343
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  • 22
    Electronic Resource
    Electronic Resource
    Allocation, within and between organs, and the dynamics of root length changes in two birch species (1995)
    Springer
    Oecologia 101 (1995), S. 439-447 
    Details
    ISSN: 1432-1939
    Keywords: Allocation ; Betula ; Biomass ; Nutrients ; Root length dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Spatial and temporal dynamics of biomass allocation within and between organs were investigated in seedlings of two birch species of contrasting successional status. Seedlings of Betula alleghaniensis Britt (yellow birch) and B. populifolia Marsh (gray birch) were grown for 6 weeks at two nutrient levels in rectangular plexiglass containers to allow non-destructive estimates of root growth, production and loss. Leaf area and production were simultaneously monitored. Yellow birch responded more to nutrient level than gray birch in terms of total biomass, shoot biomass, leaf area and root length. Yellow birch also flexibly altered within-organ allocation (specific leaf area, specific root length and specific soil amount). In contrast, gray birch altered between-organ allocation patterns (root length:leaf area and soil amount:leaf area ratios) more than yellow birch in response to nutrient level. Yellow birch showed greater overall root density changes within a very compact root system, while gray birch showed localized root density changes as concentric bands of new root production spread through the soil. Species differ critically in their responses of standing root length and root production and loss rates to nutrient supply. Early successional species such as gray birch are hypothesized to exhibit higher plasticity in varied environments than later successional species such as yellow birch. Our results suggest that different patterns of allocation, within and between plant organs, do not necessarily follow the same trajectories. To characterize thoroughly the nature of functional flexibility through ontogeny, within- and between-organ patterns of allocation must be accounted for.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00329422
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  • 23
    Electronic Resource
    Electronic Resource
    Regenerating temperate forest mesocosms in elevated CO2: belowground growth and nitrogen cycling (1997)
    Springer
    Oecologia 113 (1997), S. 115-125 
    Details
    ISSN: 1432-1939
    Keywords: Key wordsBetula ; CO2 ; Mycorrhizal fungi ; Nitrogen ; Pool dilution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The response of temperate forest ecosystems to elevated atmospheric CO2 concentrations is important because these ecosystems represent a significant component of the global carbon cycle. Two important but not well understood processes which elevated CO2 may substantially alter in these systems are regeneration and nitrogen cycling. If elevated CO2 leads to changes in species composition in regenerating forest communities then the structure and function of these ecosystems may be affected. In most temperate forests, nitrogen appears to be a limiting nutrient. If elevated CO2 leads to reductions in nitrogen cycling through increased sequestration of nitrogen in plant biomass or reductions in mineralization rates, long-term forest productivity may be constrained. To study these processes, we established mesocosms of regenerating forest communities in controlled environments maintained at either ambient (375 ppm) or elevated (700 ppm) CO2 concentrations. Mesocosms were constructed from intact monoliths of organic forest soil. We maintained these mesocosms for 2 years without any external inputs of nitrogen and allowed the plants naturally present as seeds and rhizomes to regenerate. We used 15N pool dilution techniques to quantify nitrogen fluxes within the mesocosms at the end of the 2 years. Elevated atmospheric CO2 concentration significantly affected a number of plant and soil processes in the experimental regenerating forest mesocosms. These changes included increases in total plant biomass production, plant C/N ratios, ectomycorrhizal colonization of tree fine roots, changes in tree fine root architecture, and decreases in plant NH4 + uptake rates, gross NH4 + mineralization rates, and gross NH4 + consumption rates. In addition, there was a shift in the relative biomass contribution of the two dominant regenerating tree species; the proportion of total biomass contributed by white birch (Betula papyrifera) decreased and the proportion of total biomass contributed by yellow birch (B. alleghaniensis) increased. However, elevated CO2 had no significant effect on the total amount of nitrogen in plant and soil microbial biomass. In this study we observed a suite of effects due to elevated CO2, some of which could lead to increases in potential long term growth responses to elevated CO2, other to decreases. The reduced plant NH4 + uptake rates we observed are consistent with reduced NH4 + availability due to reduced gross mineralization rates. Reduced NH4 + mineralization rates are consistent with the increases in C/N ratios we observed for leaf and fine root material. Together, these data suggest the positive increases in plant root architectural parameters and mycorrhizal colonization may not be as important as the potential negative effects of reduced nitrogen availability through decreased decomposition rates in a future atmosphere with elevated CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050359
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  • 24
    Electronic Resource
    Electronic Resource
    Physiological ecology of Juniperus virginiana in oldfields (1976)
    Springer
    Oecologia 23 (1976), S. 75-82 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Juniperus virginiana plants grow faster than other associated tree species in abandoned fields. During the summer the needles of the species do not light saturate even at 1,750 μE m-2 s-1, reach optimum photosynthesis at ∼20°C, and maintain maximum photosynthesis at-8 to-12 bar twig water potential. In the field, the plants experience pronounced daily changes in water potential. The magnitude of the changes becomes more pronounced later in the summer. Leaves of the mature plants have highest rate of photosynthesis, young trees intermediate, and seedlings lowest. In winter there is a slight shift in optimum temperature for photosynthesis and the plants photosynthesize at 0°C. The rates of photosynthesis are lower in winter than in summer. On sunny days with calm winds, mature individuals and seedlings maintain significantly higher temperatures than air temperature while intermediate plants do not. The latter exhibit a lower photosynthetic rate than both mature plants and seedlings. The trends of photosynthesis, in the 3 size classes, both in winter and summer, correspond to the chlorophyll content of their leaves. It is concluded that J. virginiana grows well in open field habitats because it is a sun-adapted, drought resistant species with a long growing season which includes winter. The species is excluded from mature forests because it is shade-intolerant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351216
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  • 25
    Electronic Resource
    Electronic Resource
    Plasticity of seed output in response to soil nutrients and density in Abutilon theophrasti: implications for maintenance of genetic variation (1997)
    Springer
    Oecologia 112 (1997), S. 35-41 
    Details
    ISSN: 1432-1939
    Keywords: Key words Abutilon theophrasti ; Genetic variation ; Plant size ; Phenotypic plasticity ; Reproductive allocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Seed output is determined by two processes: resource acquisition and the allocation of resources to seeds. In order to clarify how the reaction norm of seed output is controlled by the phenotypic expression of its two components, we examined the genetic components of plasticity of seed dry mass, plant size, and reproductive allocation under different conditions of soil nutrient availability and conspecific competition among eight families of Abutilon theophrasti. Without competition, the reaction norm of seed mass of the families crossed between the lowest and other nutrient levels, although neither of its components, plant size and reproductive allocation, showed such a response. The crossing reaction norm (i.e., reversal of relative fitnesses of different genotypes along the environmental gradient) of seed mass resulted from (1) a trade-off between plant size and reproductive allocation, and (2) changes in the relative magnitude of genetic variances in plant size and reproductive allocation with soil nutrient availability. While allocation was more important in determining seed mass under limiting nutrient conditions, plant size became more important under high-nutrient conditions. There were no significant genetic variances in seed mass, plant size, and reproductive allocation in the competition treatment, except at the highest nutrient level. The results show that plant competition mitigated the effects of genetic differences in plant performance among the families. We discuss the results in relation to maintenance of genetic variation within a population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050280
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  • 26
    Electronic Resource
    Electronic Resource
    In situ measurements of carbon dioxide gradients in a soil-plant-atmosphere system (1973)
    Springer
    Oecologia 12 (1973), S. 161-167 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In order to more fully understand carbon dioxide dynamics in a soil-plant-atmosphere system, an in situ sampling technique has been developed to measure carbon dioxide concentration within the soil profile as well as in the atmosphere. Gas samples are automatically pumped in sequence from six porous collectors within the soil profile and five aboveground inlets through an infrared gas analyzer. Field measurements in a first year field, indicated that carbon dioxide concentrations reached a maximum value (∼1800 ppm) in the deepest soil sampling site (-180 cm). Temporal and spatial variations of carbon dioxide concentration were related to the development of root and vegetation structure as well as the position of the groundwater table.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00345515
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  • 27
    Electronic Resource
    Electronic Resource
    Seed germination in relation to salt concentration in three populations of Prosopis farcta (1973)
    Springer
    Oecologia 13 (1973), S. 73-80 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Prosopis farcta (Banks et Sol.) Eig., is a widespread perennial shrub in a variety of habitats over a large geographic area in the Middle East. In iraq it occurs in non-saline deserts of the west and saline agricultural lands of the Mesopotamian Plain. The species is economically important as fuel for a sizable segment of the population in rural areas. Seeds were collected in three environmentally distinct habitats, with regard to annual precipitation and soil salt content. The seeds were germinated in various concentrations of sodium chloride and their germination, seedling radicle growth, and dark respiration studied. The results indicate that the three populations differend in their response to NaCl with the northern population being generally more sensitive than the other two populations. The three populations represent “salt ecotypes” of this very widely distributed shrub. The salt ecotypes seem to be of somewhat recent origin and apparently have been further spread by improper agricultural land-use which created vast saline areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379620
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  • 28
    Electronic Resource
    Electronic Resource
    Photosynthetic capacity in relation to leaf position in desert versus old-field annuals (1981)
    Springer
    Oecologia 50 (1981), S. 109-112 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Desert annuals of Death Valley, California have higher average light-saturated photosynthetic capacities and leaf nitrogen contents than do early-successional annuals of Illinois. The leaves of annuals in the light-unlimited Death Valley environment change little in specific weight, nitrogen, or photosynthetic capacity with age. In contrast, these properties decrease markedly with age in the leaves of the Illinois annuals even in leaves not exposed to the usual shading that accompanies canopy development. These results are interpreted in a carbon-gained-per-nitrogen-invested context.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378802
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  • 29
    Electronic Resource
    Electronic Resource
    CO2-induced growth enhancements of co-occurring tree species decline at different rates (1993)
    Springer
    Oecologia 96 (1993), S. 478-482 
    Details
    ISSN: 1432-1939
    Keywords: Elevated CO2 atmospheres ; Forest productivity ; Quercus ; Betula ; Acer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To elucidate how enriched CO2 atmospheres, soil fertility, and light availability interact to influence the long-term growth of tree seedlings, six co-occurring members of temperate forest communities including ash (Fraxinus americana L.), gray birch (Betula populifolia), red maple (Acer rubrum), yellow birch (Betula alleghaniensis), striped maple (Acer pensylvanicum), and red oak (Quercus rubra L.) were raised in a glasshouse for three years in a complete factorial design. After three years of growth, plants growing in elevated CO2 atmospheres were generally larger than those in ambient CO2 atmospheres, however, magnitudes of CO2-induced growth enhancements were contingent on the availability of nitrogen and light, as well as species identity. For all species, magnitudes of CO2-induced growth enhancements after one year of growth were greater than after three years of growth, though species' growth enhancements over the three years declined at different rates. These results suggest that CO2-induced enhancements in forest productivity may not be sustained for long periods of time. Additionally, species' differential growth responses to elevated CO2 may indirectly influence forest productivity via long-term species compositional changes in forests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00320504
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  • 30
    Electronic Resource
    Electronic Resource
    Elevated CO2 and plant nitrogen-use: is reduced tissue nitrogen concentration size-dependent? (1993)
    Springer
    Oecologia 93 (1993), S. 195-200 
    Details
    ISSN: 1432-1939
    Keywords: Allometry ; C/N Balance ; Global change ; Nitrogen-use efficiency ; Physiological adjustments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plants often respond to elevated atmospheric CO2 levels with reduced tissue nitrogen concentrations relative to ambient CO2-grown plants when comparisons are made at a common time. Another common response to enriched CO2 atmospheres is an acceleration in plant growth rates. Because plant nitrogen concentrations are often highest in seedlings and subsequently decrease during growth, comparisons between ambient and elevated CO2-grown plants made at a common time may not demonstrate CO2-induced reductions in plant nitrogen concentration per se. Rather, this comparison may be highlighting differences in nitrogen concentration between bigger, more developed plants and smaller, less developed plants. In this study, we directly examined whether elevated CO2 environments reduce plant nitrogen concentrations independent of changes in plant growth rates. We grew two annual plant species. Abutilon theophrasti (C3 photosynthetic pathway) and Amaranthus retroflexus (C4 photosynthetic pathway), from seed in glass-sided growth chambers with atmospheric CO2 levels of 350 μmol·mol−1 or 700 μmol·mol−1 and with high or low fertilizer applications. Individual plants were harvested every 2 days starting 3 days after germination to determine plant biomass and nitrogen concentration. We found: 1. High CO2-grown plants had reduced nitrogen concentrations and increased biomass relative to ambient CO2-grown plants when compared at a common time; 2. Tissue nitrogen concentrations did not vary as a function of CO2 level when plants were compared at a common size; and 3. The rate of biomass accumulation per rate of increase in plant nitrogen was unaffected by CO2 availability, but was altered by nutrient availability. These results indicate that a CO2-induced reduction in plant nitrogen concentration may not be due to physiological changes in plant nitrogen use efficiency, but is probably a size-dependent phenomenon resulting from accelerated plant growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317671
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