Master's Theses

Document Type

Thesis - campus only access

Date of Award

Spring 1959

Degree Name

Master of Science (MS)

Department

Biology

Advisor

Committee Chair

Abstract

Exclosures have been used for some time in plant ecology, particularly in the study of regeneration and re-vegetation. This study had two main purposes. One was an attempt to use long-established exclosures to determine the effect of moderate grazing on mixed prairie vegetation. The second purpose was an attempt to determine if cattle graze more heavily around the exclosure fence than a short distance away, producing a vegetative condition that differs in basal cover and species composition from the vegetation a short distance from the exclosure fence. Two exclosures were used in this study. These were designated as exclosure II and IV. Exclosure II contained two plant communities; an upland site, dominated by blue grana (Bouteloua gracilis) and buffalo grass (Buchloe dactyloides), and a hillside site on which the principal grasses were big bluestem (Andropogon gerardi), little bluestem (Andropogon scoparius), side- oats grama (Bouteloua curtipendula) and blue grama. Exclosure IV was located on a hillside site and the principal brasses were little bluestem, big bluestem, and side-oats grama. Vegetation inside and outside of exclosures was analyzed to determine the effect of grazing. Three rectangular areas, each five meters wide, were staked out adjacent to each other on every side of each exclosure. These areas were equal in length to the side of the exclosure to which they were adjacent and were used to determine the presence or absence of vegetative changes as the distance from the exclosure fence increased. All vegetation analyses were made with the point transect method. The textural quality of the soils around each exclosure was also determined to account for vegetation changes due to soil differences. The results of the study showed that it is possible to use exclosures to study the effect of grazing on vegetation. A definite difference in basal cover and species composition existed between the inside and outside of both exclosures on each site studied. The General trend was that decreased species such as big blue stem and little bluestem were more abundant inside the exclosure than outside. A corresponding increase in increaser species, such as blue grama, buffalo grass, and side-oats grama, was noted. Analyses of the vegetation inside and outside Exclosure II and IV indicated that a division of the community known as the little bluestem habitat, may be possible. The area on which Exclosure II is located appears to be more of a calcareous upland, more closely related to the upland vegetation while the area on which exclosure IV is located is the true little bluestem habitat. The results of the study on the degree of grazing as related to proximity to the exclosure fence indicated that the presence or absence of this effect varies greatly with the species studied and the location of the area studied. Big bluestem and little bluestem seem to be the most responsive species to this edge effect. On the upland site the edge effect was not present.

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© 1959 Gary K. Hulett

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