Domestic livestock grazing on mountain meadows of the Sierra Nevada is highly controversial and has been associated with negative effects on meadow species and function. In light of these effects, the US Forest Service has implemented policy and grazing management changes over the last 20 years, including the Sierra Nevada Forest Plan Amendment, which offered increased restrictions on grazing and protection for endangered meadow species. Here we ask how policy-driven changes in grazing management and precipitation have influenced trends in plant community characteristics and function in high elevation meadows. We surveyed long-term monitoring sites on 30 meadows across 12 US Forest Service grazing allotments at approximately five-year intervals from 1999 to 2010. During the study period there were significant increases in species richness and diversity, but no significant changes in species evenness and soil stability provided by the plant community. Whether the site was grazed was not significantly correlated to changes in any of the plant community metrics, but precipitation and the frequency of perennial grasslike species were negatively related to species richness and diversity. The effects of precipitation on species evenness and soil stability were dependent upon site type, with the wettest meadow sites showing greater decreases in species evenness and increases in soil stability with increasing precipitation. These findings suggest that the current levels of grazing pressure, as enforced under the Sierra Nevada Forest Plan Amendment are not hindering the dynamics of mountain meadow plant communities. In the projected climate scenarios of a longer and drier growing season in the Sierra Nevada, the implications of the relationships between precipitation and meadow plant community attributes and function will likely become more important to the management of these systems. As species diversity and evenness appear to be oppositely related to changes in precipitation from soil stability, managers may increasingly have to balance goals for these contrasting indicators of meadow health.

Meadows in the Sierra Nevada and Cascade mountain ranges are predominantly publically owned and have been grazed by domestic sheep and cattle for over a century. Because riparian areas and wetlands are susceptible to degradation under heavy livestock grazing, the U.S. Forest Service (USFS) implemented new riparian oriented grazing standards in the late 1990s. This study examined the relationship between long-term (10 years) meadow plant community trends and 1) site wetness, 2) precipitation, and 3) grazing to determine whether the new USFS standards are compatible with maintaining or improving mountain meadow plant communities. Site-level livestock utilization was measured at 55 meadow sites with long-term plant community monitoring data. Each site was ranked on a wetness scale from 1 (driest) to 5 (wettest). Relative precipitation (percent of 30-year normal annual precipitation during plant community monitoring period) was calculated for each site and the study period was relatively dry (less than 100% of 30-year normal precipitation) for all sites. Overall trends in species richness and diversity were positive across the 55 study sites. Trends in forbs, non-native species, and upland species were stable while trends in wetland obligate species were negative. Plant community trends were associated with site wetness, precipitation, and grazing. Relationships with grazing were often dependent on site characteristics (via interactions with precipitation and site wetness). There was no evidence that USFS riparian grazing standards were associated with undesirable plant community trends during the monitoring period. Results from this study suggest that USFS riparian grazing standards are compatible with meadow plant communities. However, because plant community responses can be dependent on site characteristics, site-specific adaptive management is recommended.

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.

Grazing by wild and domestic mammals can have small to large effects on plant communities, depending on characteristics of the particular community and of the type and intensity of grazing. The broad objective of this report was to extensively review literature on the effects of grazing on 25 plant communities of the southwestern U.S. in terms of plant species composition, aboveground primary productivity, and root and soil attributes. Livestock grazing management and grazing systems are assessed, as are effects of small and large native mammals and feral species, when data are available. Emphasis is placed on the evolutionary history of grazing and productivity of the particular communities as determinants of response. After reviewing available studies for each community type, we compare changes in species composition with grazing among community types. Comparisons are also made between southwestern communities with a relatively short history of grazing and communities of the adjacent Great Plains with a long evolutionary history of grazing. Evidence for grazing as a factor in shifts from grasslands to shrublands is considered. An appendix outlines a new community classification system, which is followed in describing grazing impacts in prior sections.

Headwater wetland meadows of the Western U.S. have great ecological value despite their limited aerial extent. The ability of meadows to perform important ecosystem functions can be impacted by human uses and management activities. Soil properties are important indicators of site quality and function. The major purpose of this project was to evaluate various soil characteristics, especially soil organic carbon (SOC), and interrelations with vegetation and hydrologic properties in montane and subalpine riparian-wetland meadows of the Sierra Nevada in the contexts of livestock grazing and hydrologic condition. Physical and chemical properties of whole soil solum samples and soils sampled by pedogenetic horizon were assessed in nineteen hydrologically functional meadows representing a range of livestock utilization in the Sierra National Forest. In addition, vegetation community composition and physical and chemical characteristics of whole solum soil samples were evaluated in riparian meadows representing a range of hydrologic condition as defined by the Properly Functioning Condition (PFC) method in the Stanislaus National Forest. Average total SOC contents were variable among meadows, but were considerably high on average at 37.2"2.87 kg C m -2 in the Sierra NF and 14.2"0.78 kg C m -2 in the Stanislaus NF. Soil moisture appeared to be an important driver of total SOC contents, while livestock utilization did not appear to influence overall C storage in hydrologically functional meadows. However, soils of more heavily grazed areas were more compacted and had slightly higher NO 3 - -N contents than more lightly grazed areas. Results of this study suggest any management activities that affect the hydrologic regime will likely impart undesirable changes in soil characteristics and plant communities.