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  • 1
    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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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Soil solution phosphate, root uptake kinetics and nutrient acquisition: implications for a patchy soil environment (1992)
    Springer
    Oecologia 89 (1992), S. 305-309 
    Details
    ISSN: 1432-1939
    Keywords: Soil phosphate ; Root kinetics ; Root proliferation ; Agropyron desertorum ; Artemisia tridentata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The importance of increased root phosphate (P) uptake kinetics, root proliferation and local increases of soil solution P (P1) for P acquisition from fertile soil microsites was explored with a simulation model and calculated uptake was compared with experimental data. Based on the partitioning of added P in microsites to P1 and P adsorbed on soil particles and the results of a dual-isotope-labeling experiment (Caldwell et al. 1991a), acquisition of P from the fertile microsites was some 20 X that of uptake from an equal volume of soil which received only water. Simulations were in general agreement and also showed that elevation of root P uptake kinetics could contribute more to the increased acquisition than did root proliferation under these circumstances. Although increased physiological uptake capacity for P has generally been considered to be of little benefit because of diffusion limitation, in patchy soil environments selective elevation of P uptake kinetics in fertile microsites may be of considerable benefit. These tests were conducted in calcareous soil which releases much less P into the soil solution than do many other soils. In many noncalcareous soils the benefits of selective elevation of root uptake kinetics would likely be greater.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317406
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