Examining the Species-Diversity-Productivity Relationship: Plant Species Richness and Light Heterogeneity Along Productivity Gradients in Southwestern Michigan
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Authors
Coppinger, James Peter
Issue Date
1999
Type
Thesis
Language
en_US
Keywords
Alternative Title
Abstract
Among terrestrial plant communities, the relationship between species diversity
and productivity is often unimodal; species diversity is often greatest at intermediate
levels of productivity. This phenomenon has often been attributed to changes in resource
heterogeneity resulting from changes in productivity. Resource-based competition theory
predicts that resource heterogeneity promotes species diversity in plant communities by
preventing competitive exclusion through niche partitioning. Applying this theory to
light remains controversial, as the relationship between light heterogeneity, productivity,
and species diversity remains enigmatic. In this study, the relationship between light
heterogeneity, species richness, and productivity was studied across plant communities in
the Allegan State Game Area in southwestern Michigan. Plant species richness was
sampled in grassland, oak/savanna, and forest community types, which encompassed a
broad gradient of productivity. Litter mass and herbaceous biomass provided an index of
annual net primary productivity. Light heterogeneity was measured and analyzed using
geostatistics to determine variance and patch size-two variables used to assess the
magnitude and scale of spatial heterogeneity. The relationship between species richness,
light heterogeneity, and productivity was unimodal. Intermediate productivity
communities (oak/savanna) exhibited both highest species richness and greatest
heterogeneity of light, indicated by large patch size and variance. Light heterogeneity
and species richness was lowest at both low and high levels of productivity, suggesting
that change in light heterogeneity with productivity may account for the unimodal nature
of the species richness-productivity relationship. These results support a positive
relationship between light heterogeneity and species richness, consistent with the
contemporary theories on resource heterogeneity and species diversity.
Description
vii, 40 p.
Citation
Publisher
Kalamazoo College
License
U.S. copyright laws protect this material. Commercial use or distribution of this material is not permitted without prior written permission of the copyright holder.