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  • 1
    Electronic Resource
    Electronic Resource
    Effect of competition on stable carbon isotope ratios of two tussock grass species (1991)
    Springer
    Oecologia 88 (1991), S. 148-151 
    Details
    ISSN: 1432-1939
    Keywords: Agropyron desertorum ; Agropyron spicatum ; Pseudoroegneria spicata ; Artemisia tridentata ; Stable carbon isotope composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Previous studies have shown that plant carbon isotope composition varies when plants experience differences in water and nutrient availability. However, none have addressed the effect of root interactions, including competition for these soil resources, on carbon isotope ratios. We studied the effect of interspecific root interactions on the productivity and carbon isotope ratios of two Great Basin tussock grass species (Agropyron desertorum and Pseudoroegneria spicata). We compared grasses grown in mixture with sagebrush (Artemisia tridentara) to grasses in similar mixtures but where root interactions with sagebrush were limited by fiberglass partitions. During both years of the study, tussocks growing in competition with sagebrush produced tissue with more negative δ13C values than grasses experiencing limited root interaction with sagebrush. The magnitude of this difference (0.5 to 0.9%) is similar to that found in other studies when soil fertility and moisture availability were altered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328416
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  • 2
    Electronic Resource
    Electronic Resource
    Plant competition for light analyzed with a multispecies canopy model (1990)
    Springer
    Oecologia 82 (1990), S. 374-380 
    Details
    ISSN: 1432-1939
    Keywords: Triticum aestirum ; Avena fatua ; Canopy photosynthesis ; Canopy model ; Light competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The importance of photosynthetic characteristics such as quantum efficiency or carboxylation efficiency for carbon gain of plants competing for light in dense stands is dependent on several environmental factors and structural features of the canopy. A quantitative analysis of photosynthesis of competing plants in mixed stands of wheat and wild oat (Avena fatua L.), a common weed of wheat, involved measuring photosynthetic parameters of individual leaves at different heights in the canopy throughout the growing season. This information combined with detailed assessments of canopy structure was used with a multispecies canopy model to evaluate the importance of different photosynthetic characteristics for carbon gain in this canopy environment. Independent photosynthesis data sets were used to validate predictions of the model. Carboxylation efficiency (CE) and CO2-and light-saturated photosynthetic capacity (AML) were highly correlated and decreased with depth in the canopy for both species. Quantum efficiency (α) did not tend to decrease with depth in the canopy. Sensitivity analyses with the model for whole-plant carbon gain of each species over entire day periods were conducted. These showed that changes in CE and AML had an influence similar to that of changes in α on carbon gain for both species. This was not necessarily expected from single-leaf photosynthetic behavior in response to changes in CE, AML and α. The influence of α is more pronounced in the lower, more shaded portions of the canopy than are changes in CE and AML. Appreciable differences between the species were apparent for carbon gain under different weather conditions. The differences between the species in carbon gain when in competition for light were associated more with structural features rather than with photosynthetic characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317486
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  • 3
    Electronic Resource
    Electronic Resource
    Light field heterogeneity among tussock grasses: Theoretical considerations of light harvesting and seedling establishment in tussocks and uniform tiller distributions (1994)
    Springer
    Oecologia 98 (1994), S. 241-246 
    Details
    ISSN: 1432-1939
    Keywords: Agropyron desertorum ; Canopy photosynthesis model ; Plant architeccture ; Pseudoroegneria spicata ; Resource heterogeneity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Although the tussock growth form of caespitose graminoids is widespread, the effect of this growth form on light interception and carbon gain of tillers has received little attention. Daily incident photosynthetic photon flux density (PFDinc) and carbon gain in monospecific stands of tussock grasses were compared with those of a hypothetical distribution with the equivalent tiller density per total ground area, but evenly distributed rather than clumped in tussocks. This was computed for two tussock grasses Pseudoroegneria spicata (Pursh) A. Löve (bluebunch wheatgrass) and Agropyron desertorum (Fisch, ex Link) Schult. (creasted wheatgrass) at different plant densities. Daily PFDinc and net photosynthesis (A) were greater if tillers were distributed uniformly rather than clumped in tussocks, except when the density of tussocks was so great as to approach a uniform canopy. When tussock density per ground area was low, much of the difference between tussock and uniform tiller densities in PFDinc and A was due to shading within the tussocks; up to 50–60% of the potential carbon gain was lost in A. desertorum due to shading within tussocks. In a matrix of tussocks, the light field for establishing seedlings was very heterogeneous; potential A ranged from 7 to 96% relative to an isolated seedling. The mean of daily PFDinc and A for seedlings in a tussock stand were nearly identical to the values in corresponding stands of uniform tiller distributions. It is hypothesized that the loss of A resulting from clumping tillers into tussocks is offset by benefits of protecting sequestered belowground resources from invasion by seedlings of competitors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00324210
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  • 4
    Electronic Resource
    Electronic Resource
    Plant competition for light analyzed with a multispecies canopy model (1990)
    Springer
    Oecologia 82 (1990), S. 304-310 
    Details
    ISSN: 1432-1939
    Keywords: Multispecies canopy model ; Canopy photosynthesis model ; Triticum aestivum ; Avena fatua ; Ultraviolet-B radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Competition for light among species in a mixed canopy can be assessed quantitatively by a simulation model which evaluates the importance of different morphological and photosynthetic characteristics of each species. A model was developed that simulates how the foliage of all species attenuate radiation in the canopy and how much radiation is received by foliage of each species. The model can account for different kinds of foliage (leaf blades, stems, etc.) for each species. The photosynthesis and transpiration for sunlit and shaded foliage of each species is also computed for different layers in the canopy. The model is an extension of previously described single-species canopy photosynthesis simulation models. Model predictions of the fraction of foliage sunlit and interception of light by sunlit and shaded foliage for monoculture and mixed canopies of wheat (Triticum aestivum) and wild oat (Avena fatua) in the field compared very well with measured values. The model was used to calculate light interception and canopy photosynthesis for both species of wheat/wild oat mixtures grown under normal solar and enhanced ultraviolet-B (290–320 nm) radiation (UV-B) in a glasshouse experiment with no root competition. In these experiments, measurements showed that the mixtures receiving enhanced UV-B radiation had a greater proportion of the total foliage area composed of wheat compared to mixtures in the control treatments. The difference in species foliage area and its position in the canopy resulted in a calculated increase in the portion of total canopy radiation interception and photosynthesis by wheat. This, in turn, is consistent with greater canopy biomass of wheat reported in canopies irradiated with supplemental UV-B.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317475
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  • 5
    Electronic Resource
    Electronic Resource
    Kinetic responses of Pseudoroegneria roots to localized soil enrichment (1991)
    Springer
    Plant and soil 138 (1991), S. 231-238 
    Details
    ISSN: 1573-5036
    Keywords: Agropyron spicatum ; ammonium ; kinetics ; methylammonium ; nutrient uptake ; phosphate ; potassium ; Pseudoroegneria spicata ; roots ; rubidium ; soil microsites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil patches on opposite sides of Pseudoroegneria spicata plants in the field were treated with either distilled water or a nutrient solution containing N, P, or K. Roots from these enriched and control patches were tested three days later for their capacities of ammonium, phosphate, and potassium uptake. When phosphate was augmented in the enriched patches, rates of phosphate uptake increased significantly, but not rates of ammonium or potassium uptake. When the enriched patches were augmented with nitrogen, uptake capacities of both ammonium and potassium increased significantly (mean increases of up to 88% and 71% for ammonium and potassium, respectively). Potassium augmentation did not lead to increased soil-available K and, correspondingly, did not induce changes in the capacity for uptake of K, N, or P. The potential importance of nutrient uptake kinetics in the exploitation of nutrient-rich soil patches is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00012250
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