Dissertation/Thesis Abstract

Grazing Effects on Forbs for White-Tailed Deer and Plant Species Richness
by Drabek, Dillan Joseph, M.S., Texas A&M University - Kingsville, 2020, 82; 28088864
Abstract (Summary)

Cattle (Bos spp.) grazing has been recommended as a tool to improve wildlife habitat, but available results are inconclusive and sometimes contradictory. Forbs are an important part of a white-tailed deer (Odocoileus virginianus) diet. Consumption of grass by cattle can potentially confer a competitive advantage to forbs resulting in increased forb standing crop. Forb standing crop is also strongly influenced by rainfall and soil properties. My objectives were to: 1) determine the relationship between grass disappearance resulting from herbivory and forb standing crop on the East Foundation ranches located in the Jim Hogg, Kenedy, Starr, and Willacy counties; and 2) determine how large ungulate grazing affected plant species richness. To evaluate cattle grazing effects on grass and forb standing crop and composition, I selected six 2,500 ha study sites located on the East Foundation ranches in south Texas. Fifty 1.5-m2 grazing exclosures were randomly placed in each of the six study sites. During the autumn growing season, I sampled vegetation within exclosures and at an outside paired point. I then stored the collected samples in a portable drying room trailer maintaining a temperature of 45ᵒ C, to obtain the dry mass (kg). Under the conditions this study was conducted grazing had little effect on forbs for deer. Forb standing crop was optimized (666 kg/ha) with no August rainfall and abundant September rainfall in areas with high sand percentages (90%). I found that grazing herbivores avoided low productive sites (< 562 kg/ha) and models showed that grazing use was an influence in forb production, but rainfall and sand were more important. Plant species richness was affected by grazing use more than abiotic factors in the reduced data set. My results were strongly influenced by the legacy effect of decades of overgrazing and severe drought during 2011 to 2013. Within the time frame of my study, precipitation and sand percentage were more important drivers of forb dynamics than herbivores.

Indexing (document details)
Advisor: Ortega-S., J. Alfonso
Commitee: Fulbright, Timothy E., Hewitt, David G., Campbell, Tyler A.
School: Texas A&M University - Kingsville
Department: Animal and Wildlife Science
School Location: United States -- Texas
Source: MAI 82/3(E), Masters Abstracts International
Source Type: DISSERTATION
Subjects: Range management, Wildlife Management
Keywords: Cattle (Bos spp.) grazing, White-tailed deer (Odocoileus virginianus), Forbs , Plant species richness
Publication Number: 28088864
ISBN: 9798672169156
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