http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Clonal biology of the caespitose grass Schizachyrium scoparium
mechanisms of intraclonal regulation and ecological success
Restriction of physiological integration to individual ramet hierarchies and inequitable resource acquisition among ramet hierarchies demonstrated that independence is the prevalent Schizachyrium scoparium and Bouteloua gracilis clones along an environmental gradient in the North American Great Plains. Independence among ramet hierarchies appears to be a natural consequence of the developmental architecture of grass clones, indicating that the majority of grasses exist as fragments, rather than entirely integrated clones. Nitrogen- 15, however, was effectively allocated among sequentially developed ramet generations within autonomous hierarchies of S. scoparium throughout a 2-year period. Therefore, even though independence occurs at the level of the entire clone, ramets within individual hierarchies function interdependently. Currently, the most plausible interpretation for the ecological success of the caespitose growth form is effective resource monopolization within the immediate vicinity of individual clones. Resource monopolization can reduce intra- and interspecific competition associated with neighboring clones, resulting in greater fitness for individual caespitose clones and promoting local persistence. Nutrient accumulation in soils beneath individual caespitose clones monopolizes resources and potentially functions as the mechanism conferring ecological success to caespitose grasses. For example. ecological success to caespitose grasses. For example. caespitose grasses (S. scoparium, tall- and midgrass rhizomatous grass (P. virgatum, tallgrass community), accumulated soil organic carbon and nitrogen in soils (0-5 cma depth) directly beneath the basal area of individual clones along the environmental gradient. Long-term herbivory mediated soil resource accumulation by reducing fine-grained soil heterogeneity in the tall- and midgrass communities, but enhanced it in the shortgrass community. Nutrient accumulation beneath clones, however, does not function as a regulator of ramet demography for caespitose grasses, as cumulative recruitment per ramet and estimated biomass per clone displayed a similar magnitude of change as that associated with differences in nitrogen availability. Clones within low soil volumes exhibited leaf and ramet responses, while clones within high soicomparable plasticity in volumes exhibited greatest plasticity in ramet recruitment which resulted in greater absolute changes in ramet number per clone. Consequently, caespitose clones influence biomass partitioning patterns among hierarchical (i.e., leaf-ramet- clone) levels according to soil resource availability.
"Major Subject: Rangeland Ecology and Management".
Issued also on microfiche from University Microfilms Inc.
Includes bibliographical references: pages 85-97.