Author: Leslie Michele Roche

Publisher:

Published: 2011

Total Pages:

ISBN-13: 9781124908342

Upper montane meadows are keystone areas of ecological importance within a forested landscape: Although montane meadows comprise less than 10% of the Sierra Nevada, they represent tremendous ecological, social, and economic importance. Meadows are highly productive and provide numerous ecosystem services, such as wildlife habitat, flood flow retention and maintenance of summer stream baseflows, and forage production for permitted cattle grazing. Because montane meadows provide for these multiple uses, there has been considerable concern regarding potential detrimental effects of livestock grazing on meadow functioning, especially in high elevation systems on US Forest Service lands. Public lands grazing in higher elevation range is crucial to sustaining many Sierra foothill ranching operations: In the Sierra foothills, forage quality and livestock performance is generally low throughout the inadequate dry forage period (i.e., summer season), and so managers must seek alternative feed sources (e.g., high elevation grazing leases) during this time. For these reasons, there is a growing amount of interest and examination of the potential impacts of cattle grazing on meadow functions and ecosystem services. This research was part of a larger collaborative effort, the Yosemite Toad Adaptive Management Project, between the USDA Forest Service-Pacific Southwest Region, UC Berkeley, and UC Davis. The overall project included multiple experimental approaches to investigate the potential impacts of cattle grazing on a sensitive amphibian species, Yosemite toads (Bufo canorus Camp), and its meadow habitat. In the first study, we investigated the potential to alleviate possible negative grazing impacts on hydrologic, water quality, and cover habitat conditions via cattle exclusion treatments. Our objectives were to: 1) Determine associations between breeding pool habitat conditions and use of potential breeding pools by toads, and 2) Determine how habitat conditions respond to cattle exclusion treatments on the Sierra National Forest, California. We randomly selected two toad occupied and two unoccupied breeding pools in each of nine meadows for this study (n=36 breeding pools). After baseline data collection in 2006, three meadow fencing treatments were implemented over the course of three years. Treatments were fencing to exclude cattle from the entire meadow; fencing to exclude cattle from potential toad breeding and rearing areas, with grazing allowed in the remaining unfenced portion of the meadow; and cattle grazing allowed across the entire meadow. We monitored hydrologic, water quality, and cover habitat factors as well as toad occupancy during the breeding seasons of 2006 through 2008. Concentrations of water quality constituents were uniformly low all years, regardless of treatment. Occupied pools were shallower, warmer, and more nitrogen enriched than unoccupied breeding pools. We found no evidence of improved toad breeding pool habitat conditions following fencing compared to standard US Forest Service grazing management. The second study was a three year, cross-sectional observational survey of cattle grazing intensity and Yosemite toad occupancy of meadows across the extensive grazing landscape. We surveyed biotic and abiotic factors influencing cattle utilization and toad occupancy across 24 meadows to investigate potential associations between grazing and amphibian occurrence and inform conservation planning efforts. Toad occupancy, cattle utilization, plant community, and hydrologic data were collected within each meadow. Cattle use was negatively related to meadow wetness, while toad occupancy was positively related to meadow wetness. In mid and late season (mid July through mid September) grazing periods, cattle selected for higher forage quality diets associated with drier meadows. Bayesian structural equation model analyses supported the hypothesis that meadow wetness had a greater magnitude of influence on toad meadow occupancy than cattle grazing intensity. The third study focuses on the variation in soil and plant community properties, and associated ecosystem services, across grazed meadow catenas. This patch-level (i.e., within meadow) approach allowed us to: 1) Quantify patch-level relationships among wetness, plant community characteristics, and annual cattle utilization within meadows; and 2) Quantify and describe plant community and soil characteristics expressed across meadow catenas to evaluate the variation in--and 'compatibility' of--multiple ecosystem services across grazed meadows. We found significant differences in the levels of multiple ecosystem services provided across patch types. Drier (moist to mesic) patches provided greater forage quality value, and experienced greater grazing pressures. These patches also supported greater plant species richness and diversity. The wettest patch types, produced by season-long high water tables, had the greatest accumulations of soil organic matter, soil C, and soil N. There were no significant cattle grazing impacts on soil characteristics across patch types. Collectively, these findings suggest that cattle production, wildlife conservation, and maintenance of soil properties can be compatible goals within this working landscape. Loss of critical wet meadow habitat will have direct negative impacts on sensitive aquatic species and soil health; therefore, managing current land uses to maintain proper meadow functioning conditions, restoring sites degraded from past land use activities (i.e., legacy effects), and mitigating potential climate change impacts on meadow ecohydrology are vital to conservation of multiple ecosystem services.