Effects of grazing, competition, disturbance and fire on species composition and diversity in grassland communities
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Authors: A. J. Belsky
Date: 1992
Journal: Journal of Vegetation Science
Volume: 3
Number: 2
Pages: 187-200
Summary of Methods: Individual species response to grazing, physical disturbance, competition and fire was analyzed at a population-level and community-level in the Serengeti National Park in Tanzania (34Ëš 05' E; 02Ëš 04' S). Three ecologically different grassland communities (short-, mid- and tall-grass) were examined over a five year study. Vegetative cover (live and dead biomass), species diversity and species abundance were recorded across the three sites by utilizing a point-frequency frame. Three orthogonal contrasts in addition to effects of grazing and community cover and diversity were made for each of the three grassland communities.
Article Summary / Main Points: Annuals and short-statured perennials increased in vegetative cover while tall perennials decreased in the presence of any disturbance. Species diversity decreased in plots that were protected from grazing while grazed plots increased in diversity over the five year period. Species diversity increased in plots where dominate species were removed, disturbance and early-season fire was applied. Species height and life-history can be used as a reference for predicting responses to major environmental factors. Disturbed plots that were protected from grazing recovered more quickly than disturbed plots subject to grazing. The effects of grazing and fire were found to be more influential than physical stress and competition in structuring community dynamics of grasslands.
Vegetation Types: All Grasslands
MLRA Ecoregions: Not Applicable
Agrovoc Control Words: Grazing Rangelands Community organization
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: community organization, community structure, disturbance, functional response group, grazing, herbivores, mammalian grazer, manipulation, species diversity
Annotation: This study helps illustrate the complex community dynamics in grassland ecosystems that determine population and community-level responses and organization to natural environmental factors. At the conclusion of this study, it was found that the length of examination was not sufficient to fully understand grassland responses as there was a significant absence of strong patterns of community change.
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