Livestock exclusion influences on riparian vegetation, channel morphology, and benthic macroinvertebrate assemblages
Journal of Soil and Water Conservation , 64 , 2009
Ranganath, S.C., Hession, W.C., Wynn, T.M.
Measurements in paired stream reaches with and without livestock access iii south-western Virginia suggest that livestock exclusion practices installed oil isolated streamreaches result in improved geomorphic and riparian vegetation conditions, but do not signifi-cantly improve benthic niacroinvertehrate assemblages. Numerous state and federal programsencourage agricultural producers to protect environmentally sensitive lands (such as streamsand wetlands) through the elimination of livestock access to these sensitive areas. In addi-tion to achieving soil conservation goals, it is widely believed that livestock exclusion fromstreanis will result in improvements in riparian vegetation, channel morphology, as well asinstream habitat and aquatic insect assemblages. This research assessed the changes in chan-nel morphology, riparian vegetanon, and benthic macroinvertebrate assemblages as affectedby livestock exclusion over time. Study sites consisted of paired, nearly contiguous streamreaches (five pairs), with and without active livestock access, across a range of time sincelivestock exclusion was implemented. Four of the livestock exclusion reaches ranged in timesince best management practice implementation froin I to 14 years, while one site consistedof a grazed reach paired with a reach that has been forested and without cattle access for atleast 50 years. Livestock exclusion reaches were significantly deeper, had larger iiiedian riffle substrate, and scored higher oil Reach Condition Index (a qualitative geomorphic assess-ment methodology). The livestock exclusion reaches also had significantly higher ripariangroundcover vegetation bioinass; however, the benthic macroinvertebrate assemblages werenot significantly different. The only parameter that showed correlation with time since live-stock exclusion was the Reach Condition Index, which increased (indicating improved hankstability) with time since livestock exclusion. ()ill- observations suggest that, while livestock exclusion From streanis has positive impacts oil best management practice miplemen_tation along short stream stretches does not have the desired instream benefits. In particular,bentlsic n1acroinvertebrate response depends more on upstream watershed-scale conditionsand impacts than localized, reach-scale livestock-access issues. Therefore, a more targetedapproach addressing entire stream lengths and the associated watersheds may be required torestore the integrity of aquatic ecosystems.