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As the largest biogeochemically active terrestrial reserve of carbon (C), soils have the potential to either mitigate or amplify rates of climate change. Ecosystems with large C stocks and high rates of soil C sequestration, in particular, may have outsized impacts on regional and global C cycles. Montane meadows have large soil C stocks relative to surrounding ecosystems. However, anthropogenic disturbances in many meadows may have altered the balance of C inputs and outputs, potentially converting these soils from net C sinks to net sources of C to the atmosphere. Here, we quantified ecosystem-level C inputs and outputs to estimate the annual net soil C flux from 13 montane meadows spanning a range of conditions throughout the California Sierra Nevada. Our results suggest that meadow soils can be either large net C sinks (577.6 ± 250.5 g C m−2 y−1) or sources of C to the atmosphere (− 391.6 ± 154.2 g C m−2 y−1). Variation in the direction and magnitude of net soil C flux appears to be driven by belowground C inputs. Vegetation species and functional group composition were not associated with the direction of net C flux, but climate and watershed characteristics were. Our results demonstrate that, per unit area, montane meadows hold a greater potential for C sequestration than the surrounding forest. However, legacies of disturbance have converted some meadows to strong net C sources. Accurate quantification of ecosystem-level C fluxes is critical for the development of regional C budgets and achieving global emissions goals. [ABSTRACT FROM AUTHOR]

Though typically limited in aerial extent, soils of high-elevation riparian wetlands have among the highest density of soil carbon (C) and nitrogen (N) of terrestrial ecosystems and therefore contribute disproportionally to ecosystem services such as water retention, forage production, wildlife habitat, and reactive N removal. Because much soil C and N is stored in labile forms in anaerobic conditions, management activities or environmental changes that lead to drying cause mineralization of labile soil organic matter, and loss of C and N. Meadows are focal points of human activities in mountain regions, often with incised stream channels from historically heavy grazing exacerbated by extreme runoff events. To quantify soil C and N stores in montane riparian meadows across hydrologic conditions, 17 meadows between 1950- and 2675-m elevation were selected in the central Sierra Nevada Range, California, that were classified using the proper functioning condition (PFC) system. Results indicate that C and N density in whole-solum soil cores were equivalent at forest edge positions of properly functioning, functioning at-risk, and nonfunctioning condition. Soils under more moist meadow positions in properly functioning meadows have at least twice the C, N, dissolved organic C, and dissolved organic N (DON) than those under nonfunctioning meadows. Densities of total N and DON, but not C, of functioning at-risk meadows are significantly lower ( P < 0.05) than those of properly functioning meadows at mid-slope and stream-bank positions, suggesting accelerated loss of N early in degradation processes. Though variable, the soil attributes measured correspond well to the PFC riparian wetland classification system. [ABSTRACT FROM AUTHOR]

Comparative evaluations of population dynamics in species with temporal and spatial variation in life-history traits are rare because they require long-term demographic time series from multiple populations. We present such an analysis using demographic data collected during the interval 1978-1996 for six populations of western terrestrial garter snakes (Thamnophis elegans) from two evolutionarily divergent ecotypes. Three replicate populations from a slow-living ecotype, found in mountain meadows of northeastern California, were characterized by individuals that develop slowly, mature late, reproduce infrequently with small reproductive effort, and live longer than individuals of three populations of a fast-living ecotype found at lakeshore locales. We constructed matrix population models for each of the populations based on 8-13 years of data per population and analyzed both deterministic dynamics based on mean annual vital rates and stochastic dynamics incorporating annual variation in vital rates. (1) Contributions of highly variable vital rates to fitness (?s) were buffered against the negative effects of stochastic variation, and this relationship was consistent with differences between the meadow (M-slow) and lakeshore (L-fast) ecotypes. (2) Annual variation in the proportion of gravid females had the greatest negative effect among all vital rates on ?s. The magnitude of variation in the proportion of gravid females and its effect on ?s was greater in M-slow than L-fast populations. (3) Variation in the proportion of gravid females, in turn, depended on annual variation in prey availability, and its effect on ?s was 4-23 times greater in M-slow than L-fast populations. In addition to differences in stochastic dynamics between ecotypes, we also found higher mean mortality rates across all age classes in the L-fast populations. Our results suggest that both deterministic and stochastic selective forces have affected the evolution of divergent life-history traits in the two ecotypes, which, in turn, affect population dynamics. M-slow populations have evolved life-history traits that buffer fitness against direct effects of variation in reproduction and that spread lifetime reproduction across a greater number of reproductive bouts. These results highlight the importance of long-term demographic and environmental monitoring and of incorporating temporal dynamics into empirical studies of life-history evolution. [ABSTRACT FROM AUTHOR]

High nest predation rates are one of the main sources of nesting failure in passerines. Mountain meadows in the Sierra Nevada have been intensively modified, reducing meadow wetness and potentially favoring easy access for mammalian predators to reach nesting areas in the meadow interior. We conducted mammal trapping in wet and dry areas of montane meadows during May through August of 2007 and 2008 to identify the assemblage of potential mammalian nest predators and determine the relationship between activity and meadow wetness. Chipmunk (Tamias spp.) activity was primarily restricted to dry areas. Activity of Yellow-pine Chipmunks (Tamias amoenus) was >90% higher in dry versus wet areas. Deer Mice (Peromyscus maniculatus) were equally active in both site types in 2007, but declined and were only captured in wet areas in 2008. Overall activity was higher in 2007 and 2008 for both wet and dry areas (68% and 52%, respectively). Our results suggest that increasing the proportion of inundated areas in meadows may reduce small mammal activity (for instance Yellow-pine Chipmunks) and potentially reduce nest predation. [ABSTRACT FROM AUTHOR]

Great Gray Owls (Strix nebulosa) in the Sierra Nevada Mountains feed primarily on rodents, especially voles and pocket gophers. Voles have been shown to be negatively affected by cattle grazing, but effects of grazing on gophers in the Sierra Nevada Mountains are unknown. We investigated the effects of grazing on pocket gophers (Thomomys monticola and T. bottae) in 21 grazed and 21 ungrazed montane meadow sites in the central Sierra Nevada Mountains of California. Pocket gopher densities were significantly higher in grazed meadows than ungrazed meadows. Vegetation cover and height, thatch depth, and the frequency of sedge occurrence were higher in ungrazed meadows and there were negative correlations between pocket gopher densities and these vegetation variables. We suggest that potential negative effects of grazing on Great Gray Owls could be minimized by managing meadow vegetation commensurate with the habitat needs of their prey. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the emergence of bats in Lake Tahoe Basin's highly impacted environment. The researchers categorized the study sties into two basic groups which include the area within the meadows and along the creeks. Several acoustic surveys were also conducted with the use of ultrasonic detectors and cassette data recorders to evaluate the richness and frequency of the bat species and occupancy. It shows that there were at least five species that occupied on creek and meadow sites, with or without the restoration of the lake.

1. Throughout arid regions of the world, groundwater is extracted for human population centres. In the Great Basin and Range region of the USA, we lack basic information regarding some plant communities detailing the extent to which vegetation is threatened by groundwater extraction. This is particularly true for alkali meadow vegetation, which is restricted to zones of shallow groundwater yet is not a riparian plant community with obligate wetland properties. 2. To increase our understanding of the relative importance of groundwater and precipitation in maintaining alkali meadow vegetation cover, we used a 16-year record of plant cover derived from satellite data of Owens Valley, California, USA, in conjunction with concurrent depth-to-water and precipitation measurements, to analyse vegetation response to anthropogenic and climatic changes in water availability. 3. Groundwater decline varied from 0·5 to 5·0 m throughout the study area, with the largest changes occurring at sites closest to pumping wells. The entire region experienced a 6-year drought (1987–92), during which annual precipitation remained below the 50-year median. 4. Meadow plant cover over the 16-year study period was correlated with groundwater depth, but plant cover was generally unresponsive to annual precipitation variability. Sensitivity to groundwater decline was greatest for plots with a higher cover of herbaceous perennials. 5. The results showed that this plant community is groundwater dependent, and that this characteristic buffers the system from the effects of drought. However, at sites with extensive groundwater decline, the remaining plant cover became weakly correlated with precipitation only after groundwater declined below a threshold depth located at 2·5 m, representing the average plant rooting depth. 6. Synthesis and applications. Sustainable water development that seeks to pump groundwater without adversely affecting vegetation cover and plant assemblages must recognize the maximum rooting depth of groundwater-dependent plant species. When groundwater is within the root zone, management decisions can be made to either increase or decrease vegetation cover through modification of groundwater depth. When groundwater is below the root zone, vegetation cover is low and susceptible to changes in precipitation. Quantitative satellite measurements of vegetation cover might aid the monitoring and sustainable management of water resources. [ABSTRACT FROM AUTHOR]

For many avian species, predation is the leading cause of nest failure. However, relationships between predator abundance and nest predation often differ across spatial scales. We examined the relationship between environmental characteristics in meadows and mammalian predator activity, the relationship between predator activity at 2 spatial scales, and the probability of nest predation of willow flycatchers (Empidonax traillii), dusky flycatchers (Empidonax oberholseri), and yellow warblers (Dendroica petechia) in the central Sierra Nevada Mountains, California, USA. Environmental characteristics associated with the detection of nest predators varied depending on species. Douglas's squirrel (Tamiasciurus douglasii) and chipmunks (Tamias spp.) were associated with characteristics common along edges of meadows; short-tailed weasels (Mustela erminea) were associated with willows, whereas mice (Peromyscus maniculatus, Reithrodontomys megalotis, and Microtus spp.) and long-tailed weasels (Mustela frenata) were distributed throughout the meadows. The probability of predation of willow and dusky flycatcher nests increased with increasing short-tailed weasel activity, and the probability of predation of yellow warbler nests increased with increasing activity of chipmunks and short-tailed weasels. Variation in the occurrence of predator species in different areas of the meadows likely influences the probability of nest predation by each species and the nesting success of birds. Identifying factors that influence the distribution and abundance of common nest predators will likely be integral to the development of conservation efforts to increase the reproductive success of some bird species. [ABSTRACT FROM AUTHOR]

1. Disturbance is widely believed to facilitate invasions by exotic plants but is also important for the persistence of many native species. Here I report the results of a series of field experiments designed to investigate the effects of soil disturbance on natives and aliens in Californian grassland vegetation. I also compare the effects of different types of soil disturbance to establish whether some favour aliens to a greater degree than others. 2. In two experiments, conducted at different locations. three types of soil disturbance (excavation burial and simulated gopher mounds) were created, and their revegetation was compared with changes in undisturbed control plots over the next three years. A third experiment was used to provide data on the effects of soil disturbance on soil temperature moisture and KCI-extractable nitrogen 3. Disturbance affected both soil temperature and chemistry. Buried plots contained the most KCI-extractable nitrogen, and were also the warmest. Effects on soil moisture were relatively small. 4. Initially, most disturbances greatly reduced the numerical abundance both of groups dominated by natives (perennial graminoids and bulbs) and of groups dominated by aliens (annual grarminoids Disturbance also reduced maximal (summer) species richness but in some cases increased the fraction of richness contributed by natives. 5. In subsequent years richness rebounded as natives and exotics re-invaded. Native bulbs and perennial grarminoids were slow to recover instead, most disturbances increasingly became numerically dominated by exotic annual grasses, accentuating the effects of a multi-year drought. 6. The differing effects of experimental disturbances on aliens and natives can best he explained by considering relationships between sources of propagules life histories and geographical origins. 7. Some types of disturbance were less damaging to native-dominated groups than others, but most ultimately favoured exotic. Consequently, it may be difficult to develop management strategies that preserve the diversity of disturbance-dependent natives while still excluding weedy aliens. [ABSTRACT FROM AUTHOR]