Effect of plains pocket gopher (Geomys bursarius) small-scale disturbance on the structure and composition of a tallgrass prairie plant community
Date
1997
Authors
Wolfe-Bellin, Kelly S.
Major Professor
Advisor
Moloney, Kirk A.
Committee Member
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Abstract
As the tallgrass prairie that once covered most of central North America has become increasingly fragmented, the diversity of native plant species on prairie remnants has declined. In this thesis, the effects of mounds, created by the burrowing activity of the plains pocket gopher (Geomys bursarius), on the diversity, composition, and structure of the plant community on a tallgrass prairie remnant were investigated. The vegetation dynamics on individual gopher mounds undergoing succession were followed for two years. Vegetation cover, species richness, and species diversity all increased on mounds over time, but after two years of succession, each remained significantly lower on mounds than in undisturbed areas. Vegetation cover on mounds was predicted to recover to undisturbed levels by the third growing season, but richness and diversity could take from six to eleven years to recover on mounds.
Most of the individual species found with greater frequency on mounds than off mounds were introduced exotics in the tallgrass prairie region, while all those growing with greater frequency in undisturbed areas were native perennials. Forb species, species that produce small seeds, and short-lived species composed a greater proportion of the total species count on mounds after two years of succession than in undisturbed sites. These results suggest that the clustered production of gopher mounds in space and time could have significant large-scale spatial and temporal impacts on the structure and composition of the plant community across prairie remnants. In addition, the effect of gopher mounds on the distribution and life history of a representative annual forb species, Medicago lupulina, was investigated.
A strong spatial affinity between M. lupulina distribution and that of mounds produced during the previous growing season was detected. Germination was significantly greater in undisturbed sites, but survivorship, plant biomass, and reproduction were all significantly greater on mounds. The strong dependence of this plant species on mounds for survivorship provides insight as to the importance of small-scale disturbances in maintaining species diversity and structure in the plant communities of tallgrass prairie remnants.
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thesis