Balancing agricultural and conservation outcomes in expansive grazed landscapes is a significant land management challenge across the globe. Conservation of streams and riparian areas is of particular interest due to the many critical ecosystem services they support, such as wildlife habitat, clean water, and agricultural production. Grazing managers use a suite of tools to optimize the spatial distribution of livestock across the landscape and limit livestock damage to streams and riparian areas. Accurately assessing the impact of grazing management practices on the complex network of biotic and abiotic processes that drive riparian ecosystem health can be challenging, though. This research consists of two cross-sectional surveys of riparian areas and associated stream reaches in arid, grazed landscapes in northeastern and central California aimed at better understanding relationships between grazing management and conservation outcomes.
The first study examined relationships between implementation of common grazing management practices and riparian health across 39 riparian areas and associated stream reaches. Stream macroinvertebrate assemblage was sampled at each site as an integrative metric of riparian area and associated stream health. Site specific environmental conditions and grazing management data were also collected at each site. Linear mixed effects regression analysis indicated that total livestock distribution effort (days/year) was positively correlated to two sensitive macroinvertebrate metrics: total macroinvertebrate richness and intolerant taxa richness; and the presence of off-stream water attractants was negatively correlated with one insensitive macroinvertebrate metric: tolerant taxa abundance. Our results highlight that with appropriate managerial investment, these practices can reduce negative impacts of grazing on riparian areas and improve riparian conditions in grazed landscapes.
The second study examined quantitative and qualitative indicators of ecosystem health in response to gradients of short- and long-term grazing pressure across riparian mountain meadows on U.S. Forest Service grazing allotments. Impact evaluations often measure only one aspect of ecosystem health, such as hydrology, vegetation, or habitat quality. It has been suggested that a holistic evaluation including multiple measures of ecosystem health will provide a more complete understanding of grazing impacts on these sensitive ecosystems. We used quantitative aquatic macroinvertebrate and plant community indicators, and qualitative stream visual assessment indicators to examine three metrics of ecosystem health: (1) in-stream biotic integrity, (2) riparian plant community integrity, and (3) stream channel hydrologic integrity. Short-term grazing pressure was measured as the current year’s herbaceous forage utilization and physical alteration of streambanks. Long-term grazing pressure was measured as fecal density (pats/ha), which represents five to ten years cumulative grazing pressure. Results suggest that a combination of quantitative and qualitative data addressing multiple aspects of ecosystem health provides a more complete assessment of short- and long-term grazing impacts on riparian mountain meadow ecosystems, which can help land managers ensure both conservation and agricultural goals are being met.
|Advisor:||Roche, Leslie M., Tate, Kenneth W.|
|Commitee:||Safford, Hugh D.|
|School:||University of California, Davis|
|Department:||Horticulture and Agronomy|
|School Location:||United States -- California|
|Source:||MAI 81/8(E), Masters Abstracts International|
|Subjects:||Range management, Agriculture, Ecology|
|Keywords:||aquatic macroinvertebrates, best management practices, ecosystem health indicators, grazing management, riparian areas|
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