Denton, Renee .
Grazing effects on plant biodiversity and hydrology in foothill wetlands.
Western foothills of the Sierra Nevada represent some of the most biologically diverse ecosystems in California. Wetlands associated with these ecosystems are of particular interest as they represent a spatially and temporally unique yet floristically rich subset of this diversity. Swales are a class of foothill wetlands apart from springs, seeps, and intermittent streams. During the rainy season, the flush of water infiltrating the shallow, sandy upland soils flows into lowland swales before seeping into cracks in the granitic substrate as ground water recharge. Swale soils are generally loamy with a greater water holding capacity than the surrounding uplands. Swales form a network across the landscape linked directly to the uplands yet represent a small proportion of the total land area. In order to conserve foothill wetland biodiversity in the future, it will be crucial to identify the components of importance for conservation and sustainable use, and to determine how anthropogenic practices influence these components across the landscape. How will grazing as a tool, or even the absence of grazing, be used to modify the landscape? To this end, research is ongoing at the San Joaquin Experimental Range to better understand how climate variability and grazing affect plant biodiversity and related hydrologic function. Five swale complexes were selected wherein to replicate two seasonal mowing treatments and allow control plots representing release from grazing. Plant species (alpha) and patch (beta) diversity was collected for all 15 swales at the peak of flowering using the multi-scale Modified Whitaker plot method (Stolgren et al.1999). Ground water height was sampled in each swale with 2 stratified rows of 9 stand pipe piezometers. Moisture in the soil profile from ground surface to bedrock was measured using the Deviner 2000 system. Variation in total plant biomass was evaluated each season along with all other parameters for five years. Best methods for managing and restoring the structure, composition, function, and connectivity of wetland ecosystems will be developed.
Past interdisciplinary research at SJER has focused on identifying cost-effective methods of commercial livestock production, while maintaining the integrity of the surrounding foothills. More recently, research objectives expanded to examine water quality, watershed management, and integrated hardwood management. During the next twenty years, urban development is expected to usurp a good deal of the foothill vegetation type where the current land management activity is commonly livestock grazing. The foothill ecosystem may be partitioned into much smaller management units. The future of grazing in the foothills will likely involve small acreages owned by diverse groups of people grazing a greater variety of animals. In order to conserve important wetland biodiversity in the future, it will be crucial to identify the components of importance for conservation and sustainable use, and to determine how anthropogenic practices influence these components across the landscape. How will grazing as a tool, or even the absence of grazing, be used to modify the landscape?
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San Joaquin Experimental Range
1 - USDA Forest Service, Pacific Souhwest Research Station, 2081 E. Sierra Ave., Fresno, CA, 93710, USA
San Joaquin Experimental Range.
Presentation Type: Poster:Posters for Sections
Location: Hall A/Convention Center
Date: Monday, August 2nd, 2010
Time: 5:30 PM