Title page for ETD etd-08192008-232136


Type of Document Master's Thesis
Author Hughes, April Heather
Author's Email Address aprile@vt.edu
URN etd-08192008-232136
Title The effects of cattle exclusion on stream structure and function
Degree Master of Science
Department Biology
Advisory Committee
Advisor Name Title
Benfield, Ernest Fredrick Committee Chair
Aust, Wallace Michael Committee Member
Webster, Jackson R. Committee Member
Keywords
  • stream
  • cattle
  • riparian vegetation
  • shredding macroinvertebrates
  • leaf breakdown
  • fungal biomass
  • microbial respiration
  • sediment
  • nutrients
Date of Defense 2008-07-08
Availability unrestricted
Abstract
Stream ecosystems can be influenced by cattle grazing in the riparian zone due to sediment input, nutrient loading, and soil compaction, which lead to alterations of macroinvertebrate and microbial activity. Recently government programs, such as the Conservation Reserve Enhancement Program (CREP), have provided funding for farmers to exclude cattle from streams and riparian zones. Funding for CREP is limited and does not allow for post exclusion assessment. The objectives for this study were; 1) to explore whether CREP and other cattle exclusion initiatives help restore functional integrity to streams; 2) and if they do, to evaluate the time required for integrity to be restored. I predicted leaf processing (a fundamental ecosystem level function) in streams would be influenced by excluding cattle from the riparian zone due to changes in nutrient availability, sediment abundance, shredding macroinvertebrates, and microbial activity. I tested this prediction by measuring leaf processing at sites that had cattle excluded for <1 to 15 years. Breakdown rates did not correspond linearly to time since cattle exclusion. This was probably due to the opposing effects of elevated sediment versus nutrients on leaf breakdown at recently grazed sites. Leaf breakdown and shredder density were strongly correlated with riparian vegetation density. This study suggests that in addition to cattle exclusion, reforestation of woody riparian vegetation may be essential to restore functional integrity to agricultural streams.
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