Article

Cattle Grazing and Yosemite Toad (Bufo canorus Camp) Breeding Habitat in Sierra Nevada Meadows

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Abstract

Exclusion of cattle by fencing has been proposed to alleviate possible negative grazing impacts on hydrologic, water quality, and cover habitat conditions within Sierra Nevada meadows used by Yosemite toads (Bufo canorus Camp) for breeding. 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 3 yr. Treatments were fencing to exclude cattle from the entire meadow; fencing to exclude cattle from toad breeding and rearing areas, with grazing allowed in the remaining unfenced portion of the meadow; and cattle grazing allowed across entire meadow. We monitored hydrologic, water quality, and cover habitat variables 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.

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... Specific mechanisms that may degrade breeding pools and associated habitat include hoof trampling, which may fragment or widen pools and lead to water temperature increases, faster drying of pools and potential bird predation [20], consumption of herbaceous biomass, which may also increase temperatures and decrease escape cover [21,22], and deposition of nitrogenous waste, which may cause elevated ammonia, nitrite, and nitrate, all of which have been shown to decrease survival of amphibian embryos and larvae [23]. However, recent studies have shown that livestock grazing has either mixed effects [24] or no negative effects on amphibians [25,26]. For example, studies conducted in northeastern Oregon showed no significant effects of moderate grazing on Columbia spotted frog (Rana luteiventris) reproduction and short-term survival [25,27]. ...
... For example, studies conducted in northeastern Oregon showed no significant effects of moderate grazing on Columbia spotted frog (Rana luteiventris) reproduction and short-term survival [25,27]. A companion study to our work examined Yosemite toad response to a gradient of livestock utilization in Sierra Nevada meadows and found no direct effect of grazing on Yosemite toad presence [26]. Due to the reported Yosemite toad population decline and its potential link to livestock grazing, the Forest Service developed alternative management strategies for confirmed areas occupied by Yosemite toads that were actively grazed. ...
... When Yosemite toads emerge from hibernation to breed and lay eggs, meadows are characterized by shallow flooded areas. Flooding recedes as the summer progresses, resulting in pools ranging in size from > 100 m 2 in the spring to more discrete pools (~1 m 2 ) later in the season [26]. All study meadows were identified as wet (0-30 cm depth to water [19]. ...
Article
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Amphibians are experiencing a precipitous global decline, and population stability on public lands with multiple uses is a key concern for managers. In the Sierra Nevada Mountains (California, USA), managers have specifically identified livestock grazing as an activity that may negatively affect Yosemite toads due to the potential overlap of grazing with toad habitat. Grazing exclusion from Yosemite toad breeding and rearing areas and/or entire meadows have been proposed as possible management actions to alleviate the possible impact of cattle on this species. The primary objective of this study was to determine if different fencing treatments affect Yosemite toad populations. We specifically examined the effect of three fencing treatments on Yosemite toad breeding pool occupancy, tadpoles, and young of the year (YOY). Our hypothesis was that over the course of treatment implementation (2006 through 2010), Yosemite toad breeding pool occupancy and early life stage densities would increase within two fencing treatments relative to actively grazed meadows due to beneficial changes to habitat quality in the absence of grazing. Our results did not support our hypothesis, and showed no benefit to Yosemite toad presence or early life stages in fenced or partially fenced meadows compared to standard USDA Forest Service grazing levels. We found substantial Yosemite toad variation by both meadow and year. This variation was influenced by meadow wetness, with water table depth significant in both the tadpole and YOY models.
... Yosemite toads are reputed to be declining in both distribution and abundance (Sherman & Morton 1993;Drost & Fellers 1994;Jennings & Hayes 1994;Brown & Olsen 2013;US Fish & Wildlife 2014; but see Ostoja et al. 2015). Despite extensive research into the causes of mortality and declines, such as UV radiation (Sadinski 2004), exotic predators (Grasso et al. 2010), meadow grazing (Roche et al. 2012a;b;Matchett et al. 2015), pesticide use (Sadinski 2004), and chytridiomycosis (Dodge et al., in prep), no clear patterns have emerged for the entire species (Brown et al. 2015). Climate change is ostensibly one of the greatest threats to Yosemite toad breeding ecology (Viers et al. 2013; US Fish & Wildlife Service 2014), but little research has been done to connect it with declines. ...
... Yosemite toads are reputed to be declining in both distribution and abundance (Sherman & Morton 1993;Drost & Fellers 1994;Jennings & Hayes 1994;Brown & Olsen 2013;US Fish & Wildlife 2014; but see Ostoja et al. 2015). Despite extensive research into the causes of mortality and declines, such as UV radiation (Sadinski 2004), exotic predators (Grasso et al. 2010), meadow grazing (Roche et al. 2012a;b;Matchett et al. 2015), pesticide use (Sadinski 2004), and chytridiomycosis (Dodge et al., in prep), no clear patterns have emerged for the entire species (Brown et al. 2015). Climate change is ostensibly one of the greatest threats to Yosemite toad breeding ecology (Viers et al. 2013; US Fish & Wildlife Service 2014), but little research has been done to connect it with declines. ...
... Topographic complexity and climate are known to be important predictors of connectivity (Wang 2012), and the network characteristics of meadow neighborhoods contribute to breeding probability (Berlow et al. 2013), so we hypothesized that each of these was important for genetic connectivity. Anthropogenetic impacts of packstock and livestock have been studied extensively with little evidence for an impact on toad breeding ecology (Roche et al. 2012a;b;Matchett et al. 2015), although other recreational activities might also be important, such as roads and trail crossings. Finally, we considered numerous measures of hydrology and climate change. ...
... Breeding site characteristics are likely related to the short season available to the species and generally are associated with warm-water environments conducive to rapid development (Karlstrom 1962, Kagarise Sherman and Morton 1984).Mullally (1953)found that breeding ponds were usually less than 30 cm deep. During rangewide surveys for tadpoles,Brown et al. (2014)measured maximum depths of 211 breeding areas and found a median of 0.12 m with a maximum of 0.9 m.Roche et al. (2012a)also found an association between breeding occupancy and shallow, warm water. These conditions, however, pose risks to both eggs and tadpoles. ...
... Two primary questions were addressed: (1) Does livestock grazing under Forest/Sierra Nevada Forest Plan Amendment Riparian Standards and Guidelines have a measurable effect on Yosemite toad populations, and (2) What are the effects of livestock grazing intensity on key habitat components that affect survival and recruitment of Yosemite toad populations? The study included both an experimental component and a longitudinal survey across gradients of meadow hydrologies and livestock use (Tate et al. 2010, Lind et al. 2011, Roche et al. 2012a, 2012b, McIlroy et al. 2013). In the experimental component, three livestock grazing treatments were implemented and responses of Yosemite toad populations and habitat characteristics were assessed over time. ...
... Analysis of habitat conditions indicated that Yosemite toad eggs and tadpoles were associated with the warm, shallow, relatively nitrogen-enriched pools within meadows. Both breeding and non-breeding pool conditions did not differ in relation to livestock grazing/ fencing treatments, over time (Tate et al. 2010, Lind et al. 2011, Roche et al. 2012a). Partial fencing of meadows resulted in high livestock use of areas outside of fences but within the meadow and thus is not recommended as a grazing management measure to protect Yosemite toads. ...
Technical Report
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The Yosemite toad (Anaxyrus [Bufo] canorus) is endemic to the higher-elevation (> 1,980 m [> 6,500 ft]) aquatic habitats of the Sierra Nevada Mountains of California. Once historically abundant, it is estimated that this toad has been extirpated from significant portions of its historical localities, and many of its remaining populations appear depleted. Depletions and extirpations were first recognized during the 1970s, and on 29 April, 2014, the U.S. Fish and Wildlife Service added the Yosemite toad to the Lists of Endangered and Threatened Wildlife and Plants as a threatened species. In the late 1990s, the realization that these declines could rapidly place the species at risk of extinction led to a U.S. Department of Agriculture (USDA) Forest-Service-initiated multi-agency effort to develop a conservation strategy focused on attenuating the risk factors responsible. This conservation assessment is the first step toward the development of this conservation strategy and consists of three parts: (1) a synopsis of Yosemite toad ecology designed to better understand conditions necessary to provide for viable populations; (2) a review of Yosemite toad distribution and abundance over its historical geographic range to describe the risk; and (3) an evaluation of 16 risk factor categories to identify which may contribute the greatest risk to the Yosemite toad and its habitat. Yosemite toads occupy both aquatic and terrestrial habitats. They breed and rear primarily in shallow still water habitat; use meadows, springs, and terrestrial upland habitats for foraging, refuge, and movements; and overwinter in underground terrestrial sites. Tadpoles develop rapidly in very shallow, typically ephemeral aquatic habitats. Mortality through metamorphosis can be very high, with abiotic factors (desiccation and/or freezing) sometimes causing total or near loss of a year’s cohort. Mortality of small post-metamorphic toads also appears high, likely because of high overwinter mortality. The long-lived adults may be key to long-term persistence of populations given the low recruitment in some years. Post-metamorphic life stages (juveniles and adults) occupy habitats some distance from breeding sites seasonally. Little is known about seasonal movements, especially for juveniles, but movements that range several hundred meters from breeding sites are recorded for adults. The population structure and dynamics of Yosemite toads are unclear. Yosemite toads are currently recognized as one taxonomic unit, but genetic data imply that more than one discrete lineage may be concealed within what is now called Yosemite toads. Moreover, the relationship between Yosemite toads as a taxonomic unit and its closest relatives is ambiguous and needs clarification. Yosemite toads occurred on both sides of the Sierra Nevada mountain divide between the southern portion of the Lake Tahoe Basin and the headwaters of the Kings River between 1,980 m (6,500 ft) and 3,414 m (11,200 ft). Based on pre-1980 information, most (> 99 percent) of the historical range is on federal land including six national forests and two national parks; the remainder of the range is on private and state-owned lands. Historical abundance data are mostly anecdotal, but Yosemite toads were described as being common, and at least one population had several hundred individuals; these data also imply that Yosemite toads were most abundant in the elevation region above 2,438 m (8,000 ft) and below areas of permanent snow and ice. Yosemite toad information obtained since 1990 includes quantitative occurrence and abundance data. Recent occurrence data, based on a USDA Forest Service monitoring program for high elevation amphibians and other survey data, reveal patchy extirpations range wide, with Yosemite toad populations still distributed across their original range. The few data that exist on recent abundances suggest populations may be very small (< 20 adult males) compared to historical levels with relatively few large populations remaining across the geographic range. Whether these populations are persisting in small numbers or on a slow trajectory to extirpation is not known. For the 16 potential risk factors identified during the Conservation Assessment process, definitive data are generally lacking. Risk factors that affect meadow hydrology or impact the long-lived adults including in their upland nonbreeding habitats may be most significant. Further, small populations may be more vulnerable to risk factors that would be of less concern for larger populations. Given these considerations, observational data of Yosemite toad habitat and circumstantial evidence suggest that climate change, livestock grazing, recreational activity, and the amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd) may be important factors. Livestock grazing and recreational activities were identified as important to address because of their widespread occurrence, high overlap with Yosemite toad habitats, potential effects on breeding habitat (e.g., meadow hydrology) and/or adults, and the ability of participating agencies to make meaningful management changes. A Forest-Service-sponsored research project formally addressed livestock grazing. Those results indicated that when livestock grazing use occurred at levels at or below grazing standards (i.e., 30 through 40 percent use of grass and grass-like plants, depending on meadow seral stage and condition) there were no detectable differences in toad occupancy or density (of various life stages) among areas that were grazed and areas that were not grazed (e.g., fenced meadows). This study occurred over a relatively short time period (5 years) and toad densities were highly variable among meadows. The primary drivers related to toad presence and densities were water year type and meadow wetness. No formal studies have been conducted on recreational activities and the Yosemite toad. Initial studies suggest that Bd may be an important factor in Yosemite toad declines, but the results are not conclusive and this is a major information gap. Several other risk factors (fire management; locally-applied pesticides; roads; vegetation and fuels management) are more prevalent at low to mid-elevations of the species range, may affect adults in their nonbreeding habitat, and may be particularly important where they overlap with small populations. These also have the potential to be effectively addressed by management efforts of agencies participating in this conservation assessment. Habitat loss and fragmentation may result from a variety of these risk factors. Four risk factors (acid deposition, airborne contaminants, climate change, ultraviolet radiation) have effects that originate globally or extra-regionally (from the perspective of the Sierra Nevada), and as such, are largely beyond the jurisdiction of agencies participating in this assessment. Of these, climate change may pose a high risk to Yosemite toads by altering precipitation patterns that may result in significant changes to breeding habitats among other possibilities. Participating agencies may be able to respond indirectly to these global risk factors by instituting land management actions that ameliorate local risk factors and result in higher resiliency of Yosemite toad populations. Experimental and survey data have found no direct effects from introduced fish, acid deposition, and ultraviolet radiation. Ongoing research address several aspects of the ecology of the Yosemite toad. Studies are examining Yosemite toad habitat relationships, hydrology of breeding meadows, demography, movement ecology, and genetics. Conservation options for consideration in a conservation strategy for the Yosemite toad include management at multiple scales; identifying and managing within priority basins (watersheds); maintaining and restoring meadow and other habitats; and developing options for effective management of livestock grazing and recreational activities. Further research on Yosemite toad genetics, and the relationships between Yosemite toad populations and habitat and recreational activities, Bd, and climate change are proposed.
... Also in the central Sierra Nevada, Myers and Whited [13] found FIB increased in surface waters below key grazing areas on USFS allotments following the arrival of cattle. However, Roche et al. [14] found no evidence of degradation of Yosemite toad breeding pool water quality in key grazing areas on three allotments in the Sierra National Forest of central California. Examining land-use and water quality associations in watersheds throughout the Cosumnes River Basin, Ahearn et al. [15] also reported water quality conditions in upper forested watersheds, which include USFS grazing allotments, to be well below levels of ecological concern. ...
... Our nutrient results are consistent with other examinations of surface water quality in similarly grazed landscapes. In the Sierra Nevada, Roche et al. [14] found nutrient concentrations of surface waters within key cattle grazing areas (mountain meadows) to be at least an order of magnitude below levels of ecological or biological concern for sensitive amphibians. On the Wallowa-Whitman National Forest in northeastern Oregon, Adams et al. ...
Article
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There is substantial concern that microbial and nutrient pollution by cattle on public lands degrades water quality, threatening human and ecological health. Given the importance of clean water on multiple-use landscapes, additional research is required to document and examine potential water quality issues across common resource use activities. During the 2011 grazing-recreation season, we conducted a cross sectional survey of water quality conditions associated with cattle grazing and/or recreation on 12 public lands grazing allotments in California. Our specific study objectives were to 1) quantify fecal indicator bacteria (FIB; fecal coliform and E. coli), total nitrogen, nitrate, ammonium, total phosphorus, and soluble-reactive phosphorus concentrations in surface waters; 2) compare results to a) water quality regulatory benchmarks, b) recommended maximum nutrient concentrations, and c) estimates of nutrient background concentrations; and 3) examine relationships between water quality, environmental conditions, cattle grazing, and recreation. Nutrient concentrations observed throughout the grazing-recreation season were at least one order of magnitude below levels of ecological concern, and were similar to U.S. Environmental Protection Agency (USEPA) estimates for background water quality conditions in the region. The relative percentage of FIB regulatory benchmark exceedances widely varied under individual regional and national water quality standards. Relative to USEPA's national E. coli FIB benchmarks-the most contemporary and relevant standards for this study-over 90% of the 743 samples collected were below recommended criteria values. FIB concentrations were significantly greater when stream flow was low or stagnant, water was turbid, and when cattle were actively observed at sampling. Recreation sites had the lowest mean FIB, total nitrogen, and soluble-reactive phosphorus concentrations, and there were no significant differences in FIB and nutrient concentrations between key grazing areas and non-concentrated use areas. Our results suggest cattle grazing, recreation, and provisioning of clean water can be compatible goals across these national forest lands.
... However, the water quality effect reported by Joseph et al. (2016) was small compared to the effects of introduced fish on amphibian occupancy. Moreover, another study that examined water quality in Yosemite Toad (Anaxyrus [= Bufo] canorus) habitats did not find any effect (Roche et al. 2012). Adding to this ambiguity, a study in northern California found strong evidence of a positive association between Cascade Frog (Rana cascadae) breeding use and presence of cattle grazing and found weak evidence of a negative association between Cascade Frog recruitment and cattle grazing (Cole et al. 2016). ...
... Manipulative studies are needed to establish cause and effect but are logistically difficult to perform at an appropriate scale. Manipulative studies in the western US have not found clear effects but were short relative to anuran life cycles having just 2 or 3 years of post-treatment data (Adams et al. 2009;Roche et al. 2012;Pilliod and Scherer 2015). ...
Article
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Livestock grazing is an important land use in the western USA and can have positive or negative effects on amphibians. Columbia Spotted Frog (Rana luteiventris) often use ponds that provide water for cattle. We conducted a long-term manipulative study on US Forest Service land in northeastern Oregon to determine the effects of full and partial exclosures that limited cattle access to ponds used by frogs. We found weak evidence of a short-term increase in abundance that did not differ between full and partial exclosures and that diminished with continuing exclusion of cattle. The benefit of exclosures was small relative to the overall decline in breeding numbers that we documented. This suggests that some protection can provide a short-term boost to populations.
... These objectives may help maintain habitat requirements of the mountain yellow-legged frog; however, research is needed to determine the degree of residual vegetation or utilization that may benefit or affect the mountain yellow-legged frog (USDA Forest Service 2001a). Research on the effects of livestock grazing under the current SNFPA grazing S&Gs on populations and habitats of the sympatric Yosemite toad was conducted by the Forest Service (Tate et al. 2010, Lind et al. 2011, Roche et al. 2012a, Roche et al. 2012b, McIlroy et al. 2013. From 2005-2010, no differences were detected in Yosemite toad occupancy or density among fenced, partially fenced, and unfenced meadows using the current SNFPA grazing S&Gs. ...
... At a minimum, agencies should continue to manage this activity to reduce its potential impact to these species and their habitat. Research conducted by the Forest Service to address the effects of current grazing practices on the sympatric Yosemite toad (Roche et al. 2012a, Roche et al. 2012b, McIlroy et al. 2013 contributes to our understanding of grazing and amphibians generally; however, because of ecological differences between the two species, research focused on mountain yellowlegged frogs may ultimately be required to fully understand the potential impacts to these species. ...
Technical Report
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This report presents a synthesis of scientific literature and expertise regarding the mountain yellow-legged frog complex in the Sierra Nevada, which is now comprised of two species, Rana muscosa and R. sierrae. These species, which inhabit largely higher-elevation (> 1,219 m [> 4,000 ft.]) aquatic habitats of the Sierra Nevada Mountains of California and Nevada, were historically abundant. It is estimated that these frogs have been extirpated over the majority (> 92 percent) of their geographic ranges, with many of the remaining populations depleted. Depletions and extirpations, first recognized during the 1970s, have accelerated markedly since the 1990s. The realization that these patterns would rapidly place these species at risk of extinction led to a multi-agency effort to develop a Conservation Strategy focused on the recovery of mountain yellow-legged frogs in the Sierra Nevada. This Conservation Assessment is the first step toward development of the Conservation Strategy and consists of three integral parts: 1) a description of mountain yellow-legged frog ecology in the Sierra Nevada to determine conditions necessary to provide for viable populations; 2) a review of the distribution and abundance of mountain yellow-legged frogs over their Sierran geographic range to describe the risk; and 3) an evaluation of 17 risk factor categories to identify which of these may constitute the greatest risk to mountain yellow-legged frogs and their habitat in the Sierra Nevada.
... Studies suggest that livestock grazing may be compatible with Yosemite toad conservation when managed using USFS riparian grazing standards under low to moderate levels of utilization. Roche et al. (2012a) found no significant differences in the habitat conditions of occupied Yosemite toad breeding pools in meadows fenced to exclude grazing, meadows with fencing to exclude livestock from toad breeding areas only, and unfenced meadows grazed by cattle in compliance with USFS riparian grazing standards. In a companion study, McIlroy et al. (2013) found no significant effect of fencing the whole meadow or fencing toad breeding areas on the densities of Yosemite toad tadpoles and young of the year relative to unfenced meadows with cattle grazing. ...
Article
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Wet montane meadows are an important component of the Sierra Nevada, CA ecosystem that provide diverse ecological services when in functional condition. Efforts are underway to restore meadows that have been degraded from past and historic land uses. Livestock grazing is a common land use in meadows with the potential to impact Sierra meadow ecology and may be a critical determinant of restoration success. We used a systematic literature review (SLR) method to identify, review, and synthesize scientific literature about the ecological effects of livestock grazing on Sierra meadow ecology resource areas, including hydrologic function, water quality, plants, soil, fens, and fish and wildlife species. We found 47 studies that matched our search criteria for inclusion in this SLR. Livestock grazing was associated with predominantly negative effects for each resource area reviewed, suggesting that achieving functional ecological condition in Sierra meadows that are currently used for livestock grazing may be challenging. Nevertheless, there was some evidence for compatibility with certain resource areas and certain management regimes. We discuss livestock management options, ecological objectives, and research questions that emerge from the literature to help inform meadow restoration and management.
... Livestock commonly bred in the region are sheep, pigs, horses, cows, and llamas. Previous research on the influence of cattle grazing on amphibian communities has mainly focussed on wetland ponds used by aquatically reproducing amphibians and yielded variable results (Adams et al. 2009, Schmutzer et al. 2008, Roche et al. 2012, Verga et al. 2012. Some papers suggest an increased diversity and abundance of amphibians in cattle-grazed habitat (Verga et al. 2012), while other studies find the opposite (Schmutzer et al. 2008). ...
Article
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Amphibian populations have been declining worldwide for decades with a multitude of causes having been identified. Conservationists try to reverse the situation, but for many species, important information on distribution, habitat and ecology are missing, which makes the assessment of conservation priorities problematic. Although South America holds the largest number of extant amphibian species in the world, many of them are poorly studied. This is also the case for most species of Psychrophrynella, a genus of cold-adapted frogs occurring in the high Andes, the majority of which having only recently been described. We organized an extensive field survey to study the ecology of Psychrophrynella illimani, a critically endangered species endemic to a single valley in Bolivia that has not been reported on again since its discovery in 2002. We found P. illimani to be locally common and here report new localities, extending its known distribution. Furthermore, we provide new information on its morphology, ecology, and reproductive behaviour and describe for the first time its call. We also identify and discuss several threats that might affect this species’ survival.
... increased nutrient concentrations, decreased macroinvertebrate diversity) following conifer removal treatments. We used linear mixed effects (LME) and generalized linear mixed effects (GLMM) analyses to determine the occurrence and magnitude of change in each aquatic ecosystem parameter between treated/ downstream and reference/upstream sample locations before versus after treatment [56][57][58]. A separate analysis was conducted for each parameter. ...
Article
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The removal of conifers through commercial timber harvesting has been successful in restoring aspen, however many aspen stands are located near streams, and there are concerns about potential aquatic ecosystem impairment. We examined the effects of management-scale conifer removal from aspen stands located adjacent to streams on water quality, solar radiation, canopy cover, temperature, aquatic macroinvertebrates, and soil moisture. This 8-year study (2003-2010) involved two projects located in Lassen National Forest. The Pine-Bogard Project consisted of three treatments adjacent to Pine and Bogard Creeks: (i) Phase 1 in January 2004, (ii) Phase 2 in August 2005, and (iii) Phase 3 in January 2008. The Bailey Project consisted of one treatment adjacent to Bailey Creek in September 2006. Treatments involved whole tree removal using track-laying harvesters and rubber tire skidders. More than 80% of all samples analyzed for NO3-N, NH4-N, and PO4-P at Pine, Bogard, and Bailey Creeks were below the detection limit, with the exception of naturally elevated PO4-P in Bogard Creek. All nutrient concentrations (NO3-N, NH4-N, PO4-P, K, and SO4-S) showed little variation within streams and across years. Turbidity and TSS exhibited annual variation, but there was no significant increase in the difference between upstream and downstream turbidity and TSS levels. There was a significant decrease in stream canopy cover and increase in the potential fraction of solar radiation reaching the streams in response to the Pine-Bogard Phase 3 and Bailey treatments; however, there was no corresponding increase in stream temperatures. Macroinvertebrate metrics indicated healthy aquatic ecosystem conditions throughout the course of the study. Lastly, the removal of vegetation significantly increased soil moisture in treated stands relative to untreated stands. These results indicate that, with careful planning and implementation of site-specific best management practices, conifer removal to restore aspen stands can be conducted without degrading aquatic ecosystems.
... These include biogeochemical cycling, hydrologic functions (e.g., flood attenuation), maintenance of biodiversity, sediment retention, carbon sequestration, wildlife forage production, and habitat structure (Smith et al. 1995, Hruby 2009, Morton and Pereyra 2010. Meadows in the Sierra Nevada are receiving increased attention both for the ecosystem functions they provide and for the socioeconomic values related to their proper use (e.g., aesthetics, domestic animal grazing; Roche et al. 2012). ...
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Subalpine meadows are some of the most ecologically important components of mountain landscapes, and primary productivity is important to the maintenance of meadow functions. Understanding how changes in primary productivity are associated with variability in moisture and temperature will become increasingly important with current and anticipated changes in climate. Our objective was to describe patterns and variability in aboveground live vascular plant biomass in relation to climatic factors. We harvested aboveground biomass at peak growth from four 64-m2 plots each in xeric, mesic, and hydric meadows annually from 1994 to 2000. Data from nearby weather stations provided independent variables of spring snow water content, snow-free date, and thawing degree days for a cumulative index of available energy. We assembled these climatic variables into a set of mixed effects analysis of covariance models to evaluate their relationships with annual aboveground net primary productivity (ANPP), and we used an information theoretic approach to compare the quality of fit among candidate models. ANPP in the xeric meadow was negatively related to snow water content and thawing degree days and in the mesic meadow was negatively related to snow water content. Relationships between ANPP and these 2 covariates in the hydric meadow were not significant. Increasing snow water content may limit ANPP in these meadows if anaerobic conditions delay microbial activity and nutrient availability. Increased thawing degree days may limit ANPP in xeric meadows by prematurely depleting soil moisture. Large within-year variation of ANPP in the hydric meadow limited sensitivity to the climatic variables. These relationships suggest that, under projected warmer and drier conditions, ANPP will increase in mesic meadows but remain unchanged in xeric meadows because declines associated with increased temperatures would offset the increases from decreased snow water content.
... Natural disturbances such as grazing and fire may help maintain high-quality amphibian habitat but have been disrupted across the range of many species (Wilgers andHorne 2006, Burton et al. 2009). Grazed meadows can provide breeding habitat for amphibians such as the Yosemite toad (Anaxyrus canorus) when the cattle grazing is occurring at low-to-moderate levels (Roche et al. 2012), and grazing within wetlands may even improve habitat for some amphibians (e.g., bufonids [true toads]; Burton et al. 2009). However, changes in historical management practices such as grazing could result in habitat degradation if that practice was benefitting the species in the past. ...
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Understanding the limiting factors of recovery is essential for guiding sound management of endangered species. The Wyoming toad (Anaxyrus baxteri) is a critically endangered amphibian whose cause of decline and inability to reestablish breeding populations despite early life stage reintroductions remains unknown; habitat degradation and the pathogen Batrachochytrium dendrobatidis (Bd) are 2 potential contributing factors. In 2013, we experimentally tested the effects of habitat factors under food-supplemented and predator-protected conditions (i.e., mesh field enclosures) on time to metamorphosis, the proportion of tadpoles that metamorphosed, tadpole and toadlet size, the proportion of toadlets remaining in enclosures at release (approx. 1 month post-metamorphosis), and Bd prevalence in early life stages of Wyoming toads at Mortenson Lake National Wildlife Refuge. In 2014, we tested the effects of small-scale application of vegetation height management on toadlet size, the proportion of toadlets that remained, and Bd prevalence until 1 month post-metamorphosis. In 2013, median time to metamorphosis (25.5 days) was shorter in warmer water temperatures and proportion of tadpoles that metamorphosed was 0.70. In 2013, toadlet size was positively related to forb cover up to 35% and although overall treatment effect was not significant, mid-vegetation height treatments (10-30cm) had fewer small toadlets at release than short (0-10cm) and tall (>30cm) vegetation heights. In 2014, vegetation height treatment (11.49-31.6cm) had marginal support for estimating larger size at release. Batrachochytrium dendrobatidis was not detected in water samples or on post-metamorphic toadlets. Our results suggest that in mesh field enclosures, time to metamorphosis is shorter in warm water. In addition, vegetation heights of 10-30cm and up to 35% forb cover within terrestrial mesh enclosures could increase Wyoming toad post-metamorphic size, which could increase overwinter survival rates. Using mesh field enclosures for soft-release may improve the effectiveness of early life stage reintroduction efforts, but predator attraction and density-dependent growth need to be considered. Habitat management can also influence growth and survival of early life stages of amphibians and may benefit reintroduction efforts for other species.
... The magnitude of impacts can depend on a variety of factors including riparian community type and stocking and utiliza tion rates (Green and Kauffman 1995;Kauffman et al. 1983aKauffman et al. , 1983bMyers and Swanson 1991;Schulz and Leininger 1990). Both negative and positive associations between livestock grazing and amphibian populations and habitat have been found (Adams et al. 2009, Bull and Hayes 2000, Burton et al. 2009, Jansen and Healey 2003, Knutson et al. 2004, Lind et al. 2011, Roche et al. 2012. For the foothill yellow-legged frog, a retrospective study in Oregon found a negative association between grazed lands and frog occupancy (Borisenko and Hayes 1999). ...
Technical Report
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The foothill yellow-legged frog (Rana boylii) is a stream-breeding amphib­ian that has experienced significant population declines over a large portion of its historical range. This frog is nearing extirpation in much of the Sierra Nevada region where existing populations are sparse. Water development and diversions are likely to be the primary cause of population declines and are currently a prominent risk factor because they result in hydrological changes that chronically affect several aspects of the species’ life history. Other primary risk factors include climate change, mining and suction-dredging, introduced species, and habitat loss. Conservation approaches could include restoration of hydrologic attributes such as flow and thermal regimes on regulated rivers, restoration of associated uplands and connecting riparian corridors, and management of flow regimes to retain or restore favorable habitat conditions.
... For example, at a Rana luteiventris site in northeastern Oregon, Adams et al. (2009) detected no significant differences in water quality, including measures of nutrients and specific conductance, before and after grazing exclosure treatments. Similarly, Roche et al. (2012) found no significant cattle fencing treatment effect on water quality at Sierra Nevada wet meadow Anaxyrus canorus sites in California. Other studies have identified links between grazing and nitrogenous compounds (e.g., Joseph et al. 2016), fecal bacteria (e.g., Gary et al. 1983), and turbidity (e.g., Campbell and Allen-Diaz 1997). ...
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Land use alteration such as livestock grazing can affect water quality in habitats of at-risk wildlife species. Data from managed wetlands are needed to understand levels of exposure for aquatic life stages and monitor grazing-related changes afield. We quantified spatial and temporal variation in water quality in wetlands occupied by threatened Oregon spotted frog (Rana pretiosa) at Klamath Marsh National Wildlife Refuge in Oregon, United States (US). We used analyses for censored data to evaluate the importance of habitat type and grazing history in predicting concentrations of nutrients, turbidity, fecal indicator bacteria (FIB; total coliforms, Escherichia coli (E. coli), and enterococci), and estrogenicity, an indicator of estrogenic activity. Nutrients (orthophosphate and ammonia) and enterococci varied over time and space, while E. coli, total coliforms, turbidity, and estrogenicity were more strongly associated with local livestock grazing metrics. Turbidity was correlated with several grazing-related constituents and may be particularly useful for monitoring water quality in landscapes with livestock use. Concentrations of orthophosphate and estrogenicity were elevated at several sites relative to published health benchmarks, and their potential effects on Rana pretiosa warrant further investigation. Our data provided an initial assessment of potential exposure of amphibians to grazing-related constituents in western US wetlands. Increased monitoring of surface water quality and amphibian population status in combination with controlled laboratory toxicity studies could help inform future research and targeted management strategies for wetlands with both grazing and amphibians of conservation concern.
... Livestock can create water quality issues due to urination and defecation (Doran et al. 1981, Nader et al. 1998. Existing studies on the impacts of cattle grazing on amphibians have had mixed results: some studies showing negative impacts (Healy et al. 1997, Jansen and Healy 2003, Schmutzer et al. 2008) and some showing no impacts (Bull and Hayes 2000, McIlroy et al. 2013, Roche et al. 2012. McIlroy et al. (2013) suggested the conflicting results of the studies could be due to the differences in grazing intensity of the systems studied. ...
... Our results contrast with a companion study by Roche et al. (2012), who investigated two occupied and two unoccupied pools each in nine meadows (36 pools total) in 2006-2008. Across years, they found that A. canorus occupied warmer but shallower pools. ...
Article
Fine-scale habitat information can provide insight into species occupancy and persistence that is not apparent at the landscape-scale. Such information is particularly important for rare species that are experiencing population declines, such as the threatened Yosemite Toad (Anaxyrus canorus). Our study examined differences in physical characteristics of occupied and unoccupied toad breeding pools within meadows, and then used a logistic regression model to evaluate if occupancy was related to the physical microhabitat variables. We found that occupied pools on average were deeper by 0.7 cm, warmer by 3°C, and had 50% more surface water along the short axis of the pool. Mean water depth, mean water temperature, the amount of surface water in the pools, mean detritus depth, and mean vegetation height were significant predictors of toad occupancy. Despite variation in larger-scale environmental conditions such as yearly winter snow cover and precipitation, occupancy was not related to individual years and microhabitat requirements for toad occupancy appear to be relatively constant. Pools were very shallow water bodies (mean depth 4.35 cm for occupied pools), and differences in physical microhabitat variables for suitable breeding sites were small but significant. This underscores the importance of fine-scale habitat information for breeding and reproduction of A. canorus, and for species persistence and management. © 2017 by the American Society of Ichthyologists and Herpetologists.
... Results showed that both air temperature and precipitation was significant correlated with NEE (all P<0.01), but the grassland could have great potentials for C sinks under the optimum temperature and precipitation at fenced and grazed meadows, suggested that air temperature and precipitation are highly important controlling factors over ecosystem C exchange [24] in the study area. In addition, the strong seasonal and inter-annual variability in NEE, GEP and ER have also been reported in many other grassland ecosystems such as Canada grasslands [26], a California's largest serpentine grasslands [27], North Patagonia grasslands [28], and central Sierra Nevada grasslands [29]. ...
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A better understanding of the responses of various ecosystem CO2 fluxes to human activity is vital for restore degraded grasslands and mitigating global warming. However, still undefined how CO2 exchanges (e.g. net ecosystem carbon exchange, NEE; gross ecosystem productivity, GEP and ecosystem respiration, ER) will respond to the fenced and grazed at a meadow steppe northwest of China. Base on an infrared gas analyzer linked to a clear plexiglass incubation chamber, we conducted an experimental study to examine effects of fenced meadow (from 2005 to now) on NEE, GEP and ER over the growing seasons from 2012 to 2015. Results showed that net carbon up take was found in all treatments in four years, with the NEE ranging from-3.96 to-0.01 μ mol/(m 2 ·s), the cumulative values were-105.73 ± 20.80 and-99.28 ±18.43 g C/ (m 2 ·yr) for fenced and grazed meadows, respectively. Compare with grazed meadow, fenced meadow significantly increased (P<0.05) NEE (5%, 10%, 7% and 9% from 2012 to 2015, respectively) could primarily be attributed to greater stimulation of GEP than ER. These results suggested that fenced meadow prevails over grazed meadow in maintaining carbon balance in arid and semi-arid grasslands.
... A. canorus has experienced decreases in abundance at select sites and reductions in its distribution (Sherman and Morton 1993;Jennings and Hayes 1994;Drost and Fellers 1996;Green and Sherman 2001;Brown et al. 2012), leading to its current listings of threatened by the USFWS and endangered by the International Union for the Conservation of Nature (IUCN). Despite efforts investigating invasive predators, pesticide use, and meadow grazing by pack stock and cattle as drivers of declines, no clear patterns have emerged (Grasso et al. 2010;Roche et al. 2012;McIlroy et al. 2013). Our results show that A. canorus juveniles are susceptible to Bd infection and develop lethal chytridiomycosis in a controlled setting, suggesting that chytridiomycosis may be a proximate cause of decline in this species. ...
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The Yosemite Toad (Anaxyrus canorus) has experienced declines in distribution and abundance in recent decades. The declines in this species have been anecdotally attributed to infectious disease and increased frequency and intensity of drought, but neither of these factors have been formally tested. We investigated the combined effects of reduced water availability and susceptibility to the disease chytridiomycosis across A. canorus life stages. Specifically, we reared A. canorus tadpoles under drying conditions and exposed metamorphosed toadlets to Batrachochytrium dendrobatidis (Bd), the pathogenic fungus that causes the lethal disease chytridiomycosis. We examined (1) the time to and size at metamorphosis of A. canorus tadpoles reared under drying conditions, (2) the susceptibility of post-metamorphic A. canorus to Bd, and (3) the synergistic effects of drying conditions and disease on post-metamorphic toadlet survival. We found that recently metamorphosed A. canorus toadlets are highly susceptible to lethal Bd infection. Although we did not detect an effect of reduced water availability on disease risk, we suggest follow-up experiments in both the laboratory and the field to better understand the direct and indirect roles that drought and disease play in A. canorus population declines.
... Such comparisons generally offer limited application to extensive grazing systems, which commonly experience a continuum of grazing pressure. In a concurrent study within the same grazing allotments, our research group found no evidence that existing USFS grazing management impaired amphibian habitat conditions (i.e., water quality and cover) [67] . Other cattleamphibian interaction studies from extensively grazed systems have demonstrated results similar to ours. ...
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World-wide population declines have sharpened concern for amphibian conservation on working landscapes. Across the Sierra Nevada's national forest lands, where almost half of native amphibian species are considered at risk, permitted livestock grazing is a notably controversial agricultural activity. Cattle (Bos taurus) grazing is thought to degrade the quality, and thus reduce occupancy, of meadow breeding habitat for amphibian species of concern such as the endemic Yosemite toad (Anaxyrus [ = Bufo] canorus). However, there is currently little quantitative information correlating cattle grazing intensity, meadow breeding habitat quality, and toad use of meadow habitat. We surveyed biotic and abiotic factors influencing cattle utilization and toad occupancy across 24 Sierra Nevada meadows to establish these correlations and inform conservation planning efforts. We utilized both traditional regression models and Bayesian structural equation modeling to investigate potential drivers of meadow habitat use by cattle and Yosemite toads. Cattle use was negatively related to meadow wetness, while toad occupancy was positively related. In mid and late season (mid July-mid September) grazing periods, cattle selected for higher forage quality diets associated with vegetation in relatively drier meadows, whereas toads were more prevalent in wetter meadows. Because cattle and toads largely occupied divergent zones along the moisture gradient, the potential for indirect or direct negative effects is likely minimized via a partitioning of the meadow habitat. During the early season, when habitat use overlap was highest, overall low grazing levels resulted in no detectable impacts on toad occupancy. Bayesian structural equation analyses supported the hypothesis that meadow hydrology influenced toad meadow occupancy, while cattle grazing intensity did not. These findings suggest cattle production and amphibian conservation can be compatible goals within this working landscape.
Article
Pack and saddle stock, including, but not limited to domesticated horses, mules, and burros, are used to support commercial, private and administrative activities in the Sierra Nevada. The use of pack stock has become a contentious and litigious issue for land management agencies in the region inter alia due to concerns over effects on the environment. The potential environmental effects of pack stock on Sierra Nevada meadow ecosystems are reviewed and it is concluded that the use of pack stock has the potential to influence the following: (1) water nutrient dynamics, sedimentation, temperature, and microbial pathogen content; (2) soil chemistry, nutrient cycling, soil compaction and hydrology; (3) plant individuals, populations and community dynamics, non-native invasive species, and encroachment of woody species; and (4) wildlife individuals, populations and communities. It is considered from currently available information that management objectives of pack stock should include the following: minimise bare ground, maximise plant cover, maintain species composition of native plants, minimise trampling, especially on wet soils and stream banks, and minimise direct urination and defecation by pack stock into water. However, incomplete documentation of patterns of pack stock use and limited past research limits current understanding of the effects of pack stock, especially their effects on water, soils and wildlife. To improve management of pack stock in this region, research is needed on linking measurable monitoring variables (e.g. plant cover) with environmental relevancy (e.g. soil erosion processes, wildlife habitat use), and identifying specific environmental thresholds of degradation along gradients of pack stock use in Sierra Nevada meadows.
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Pastureland currently occupies 26% of Earth's ice‐free land surface. As the global human population continues to increase and developing countries consume more protein‐rich diets, the amount of land devoted to livestock grazing will only continue to rise. To mitigate the loss of global biodiversity as a consequence of the ever‐expanding amount of land converted from native habitat into pastureland for livestock grazing, an understanding of how livestock impact wildlife is critical. While previous reviews have examined the impact of livestock on a wide variety of taxa, there have been no reviews examining how global livestock grazing affects amphibians. We conducted both an empirical study in south‐central Florida examining the impact of cattle on amphibian communities and a quantitative literature review of similar studies on five continents. Our empirical study analyzed amphibian community responses to cattle as both a binary (presence/absence) variable, and as a continuous variable based on cow pie density. Across all analyses, we were unable to find any evidence that cattle affected the amphibian community at our study site. The literature review returned 46 papers that met our criteria for inclusion. Of these studies, 15 found positive effects of livestock on amphibians, 21 found neutral/mixed effects, and 10 found negative effects. Our quantitative analysis of these data indicates that amphibian species that historically occurred in closed‐canopy habitats are generally negatively affected by livestock presence. In contrast, open‐canopy amphibians are likely to experience positive effects from the presence of livestock, and these positive effects are most likely to occur in locations with cooler climates and/or greater precipitation seasonality. Collectively, our empirical work and literature review demonstrate that under the correct conditions well‐managed rangelands are able to support diverse assemblages of amphibians. These rangeland ecosystems may play a critical role in protecting future amphibian biodiversity by serving as an “off‐reserve” system to supplement the biodiversity conserved within traditional protected areas. This article is protected by copyright. All rights reserved.
Thesis
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Climate change is ostensibly one of the greatest modern selective pressures, and species with sensitive life histories or physiologies must adapt, migrate, or buffer its effects to persist. Some 15–37% of species are expected to be endangered or extinct by 2050. The most vulnerable include habitat specialists, local endemics, and species with low intrinsic growth rates. Yosemite toads (Anaxyrus canorus) are one such alpine endemic, having been extirpated from up to 69% of their historical range. Several features of their natural history make them vulnerable: small population sizes, high larval mortality, infrequent breeding, and specialized, patch-limited habitat prone to premature desiccation. In addition to their role as ecosystem flagships, Yosemite toads provide a model system for the many other specialists with similar life histories that are challenged by environmental change. The goal of this dissertation is to understand how historical evolutionary processes such as lineage divergence and secondary admixture, along with current levels of genetic connectivity, are expected to shape the future of Yosemite toad persistence in the face of climate change. The first chapter reconstructs phylogeographic patterns of lineage formation and fusion during repeated bouts of Pleistocene glaciation, and showcases a role for refugia in ecological divergence. The second chapter examines three contact zones as replicate tests of the hypothesis that loci associated with incipient speciation are distinct from those that readily cross ancient lineage boundaries. The third chapter models modern genetic connectivity as a network of environmental and climatic interactions, using a novel approach that incorporates phylogeographic structure. The fourth chapter forecasts the future selective pressure of climate change, and predicts where connectivity may be a mitigating force to restore genetic diversity. My dissertation provides an example of how conservation strategies can incorporate the many temporal processes (ancient, recent, and current) that have shaped current genetic diversity patterns, and use a “total evidence” approach to predict future adaptive potential.
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Background Meadow ecosystems have important ecological functions and support socioeconomic services, yet are subject to multiple stressors that can lead to rapid degradation. In the Sierra Nevada of the western USA, recreational pack stock (horses and mules) use in seasonally wet mountain meadows may lead to soil trampling and meadow degradation, especially when soil water content is high and vegetation is developing. Methods In order to improve the ability to predict meadow vulnerability to soil disturbance from pack stock use, we measured soil resistance (SR), which is an index of vulnerability to trampling disturbance, at two spatial scales using a stratified-random sampling design. We then compared SR to several soil and vegetation explanatory variables that were also measured at the two spatial scales: plant community type (local scale) and topographic gradient class (meadow scale). Results We found that local-scale differences in drivers of SR were contingent on the meadow scale, which is important because multiple spatial scale evaluation of ecological metrics provides a broader understanding of the potential controls on ecological processes than assessments conducted at a single spatial scale. We also found two contrasting explanatory models for drivers of SR at the local scale: (1) soil gravimetric water content effects on soil disaggregation and (2) soil bulk density and root mass influence on soil cohesion. Soil resistance was insufficient to sustain pack stock use without incurring soil deformation in wet plant communities, even when plant cover was maximal during a major drought. Conclusions Our study provides new information on seasonally wet meadow vulnerability to trampling by pack stock animals using multi-scale drivers of SR, including the contrasting roles of soil disaggregation, friction, and cohesion. Our work aims to inform meadow management efforts in the Sierra Nevada and herbaceous ecosystems in similar regions that are subject to seasonal soil saturation and livestock use.
Technical Report
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The goal of this report is to inform conservation advocates in the Sierra Nevada and Forest Service regional and forest-level planning teams, and to help set a sound scientific and policy agenda for aquatic conservation during future forest plan revisions. The first section of the report reviews the status of and threats to aquatic and water-related resources of the national forests of the Sierra Nevada. It includes assessment of the importance of those forests for region-wide conservation of aquatic biological resources and ecosystem services, including those underlying water quality and quantity. The second section is a policy analysis of land management allocations, standards and guidelines presently in effect. It provides a critical review of the elements of the current aquatic management strategy (AMS) on California’s national forests of the Sierra Nevada under the Sierra Nevada Forest Plan Amendment (SNFPA) of 2004 and the Herger-Feinstein Quincy Library Group Forest Recovery Act. The third section provides specific recommendations developed in response to three elements: 1) new and emerging science, 2) the implications of the environmental assessment in part I, and 3) the analysis of specific policy provisions in part II. This section identifies which existing policies need to be bolstered or wholly modified, or new policies that should be adopted, if aquatic and water resource conservation and restoration needs are to be effectively met in the future. A partly annotated selection of key literature sources is provided. Appendices address conservation status of forest-dwelling aquatic and riparian species of concern, detailed comments on specific provisions of the Sierra Framework AMS and ancillary guidance, and a comparison of the AMS Direction with the Lassen Salmon Strategy.
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We evaluated reproduction and recruitment of the Columbia spotted frog (Rana luteiventris Thompson) in 70 ponds used by beef cattle and in 57 ponds not used by beef cattle in northeast-ern Oregon. No significant differences were detected in the num-ber of egg masses or recently metamorphosed frogs in grazed and ungrazed sites. No pond characteristic measured could pre-dict egg mass numbers, but percent aquatic vegetation and dis-solved oxygen had some ability to predict recently metamor-phosed frog numbers. Both variables explained 65% of the vari-ability in recently metamorphosed frog numbers in grazed ponds. At ungrazed ponds, 4 additional variables (presence of fish, elevation, percent of rock, and conductivity) were required to achieve the same level of variability in predicting recently transformed frog abundance. The egg mass volume was larger at grazed than at ungrazed ponds suggesting that grazed ponds may have a greater food abundance or larger (older) individuals.
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A spectrophotometric procedure for determination of nitrate in water, soil extracts, and a variety of other sample types is described using one reagent solution which is easily prepared and stored. Sample and equipment requirements are minimal. Reduced chemical hazard, simplicity, and versatility represent improvements over existing methods. Limit of detection is 0.01 µg N mL (0.72 μM ) or less, depending on the matrix.
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We conducted a field study to determine the relative contributions of aspen (Populus tremuloides), meadow, and conifer communities to local and land-scape-level plant species diversity in the Sierra Nevada and southern Cascade Range, northeastern California, USA. We surveyed plant assemblages at 30 sites that included adjacent aspen, conifer, and meadow commu-nities across a 10,000-km 2 region. We statistically investigated patterns in local and landscape-scale plant diversity within and among the three vegetation types. Summing across sites, aspen stands supported more plant species overall and more unique plant species than either meadow or conifer communities. Local richness and diversity did not differ between aspen and meadow plots; conifer forest plots were significantly lower in both measures. Heterogeneity in species composition was higher for aspen forest than for meadows or conifer forest, both within sites and between sites. Plant communities in aspen stands shared less than 25% of their species with adjacent vegetation in conifer and meadow plots. Within aspen forest, we found a negative relationship between total canopy cover and plant diversity. Our results strongly support the idea that plant communities of aspen stands are compositionally distinct from adjacent meadows and conifer forest, and that aspen forests are a major contributor to plant species diversity in the study region. Current patterns of aspen stand succession to conifer forest on many sites in the semiarid western US are likely to reduce local and landscape-level plant species diversity, and may also have negative effects on other ecosystem functions and services provided by aspen forest.
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Livestock grazing is a common land use across the western United States, but concerns have been raised regarding its potential to affect amphibian populations. We studied the short-term effects of full and partial livestock grazing exclosures on Rana luteiventris (Columbia Spotted Frog) populations using a controlled manipulative field experiment with pre- and posttreatment data (2002–2006). Despite a significant increase in vegetation height within grazing exclosures, we did not find treatment effects for egg mass counts, larval survival, or size at metamorphosis 1–2 years following grazing exclosure installation. Water samples taken in late summer showed concentrations of nitrite, nitrate, ammonia, and orthophosphate that were low or near detection limits across all ponds and years. The results of this experiment do not support a hypothesis that limiting cattle access to breeding ponds will help conserve R. luteiventris populations in our study area. Further research is needed to evaluate regional variation and long-term effects of grazing exclosures on R. luteiventris populations.
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From 1997–1999 we studied one of four known populations of Oregon Spotted Frogs (Rana pretiosa) in Washington State to investigate patterns of range use, movements, and habitat selection. Sixty telemetered frogs occupied a range that was a mosaic of wetlands (15.6 ha) and upland pasture (13.2 ha) grazed by dairy cows. Mean (± SE) home-range size for four frogs was 2.2 ± 1.0 ha. Patterns of spatial use, determined from 654 telemetry locations, were closely related to season and changing surface water conditions. During the breeding season (February to May), frogs occupied ≥50% of the area they used the entire year, and oviposited in shallow pools (depth = 16.9 ± 0.6 cm) on the margins of an ephemeral creek. In the dry season (June to August), frogs moved down stream to deeper, permanent pools (depth = 23.6 ± 1.0 cm), significantly reduced their movements, and occupied the smallest ranges of any season. During the wet season (September to January), frogs moved back up stream and reoccupied the breeding range. During the coldest weather, frogs buried themselves at the base of dense vegetation in shallow water under ice (depth = 17.4 ± 0.8 cm). Frogs avoided dry uplands. Frogs selected sedge (Carex obnupta, and Carex utriculata)/rush (Juncus effusus) habitat during breeding and hardhack (Spiraea douglasii) cover during the dry season that shaded and maintained remnant pools. Frogs preferred microhabitats with 50–75% water surface exposure based on comparisons between telemetry locations and nearby locations that were randomly selected. Aquatic requirements necessary to complete the life cycle of Oregon Spotted Frogs in this population include (1) stable, shallow water areas for egg and tadpole survival in the breeding season, (2) deep, moderately vegetated pools for adult and juvenile survival in the dry season, and (3) shallow water levels over emergent vegetation for protecting all age classes during cold weather in the wet season.
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In some agricultural regions, natural wetlands are scarce, and constructed agricultural ponds may represent important alternative breeding habitats for amphibians. Properly managed, these agricultural ponds may effectively increase the total amount of breeding habitat and help to sustain populations. We studied small, constructed agricultural ponds in southeastern Minnesota to assess their value as amphibian breeding sites. Our study examined habitat factors associated with amphibian reproduction at two spatial scales: the pond and the landscape surrounding the pond. We found that small agricultural ponds in southeastern Minnesota provided breeding habitat for at least 10 species of amphibians. Species richness and multispecies reproductive success were more closely associated with characteristics of the pond (water quality, vegetation, and predators) compared with char-acteristics of the surrounding landscape, but individual species were associated with both pond and landscape variables. Ponds surrounded by row crops had similar species richness and reproductive success compared with natural wetlands and ponds surrounded by non-grazed pasture. Ponds used for watering livestock had elevated concentrations of phos-phorus, higher turbidity, and a trend toward reduced amphibian reproductive success. Spe-cies richness was highest in small ponds, ponds with lower total nitrogen concentrations, tiger salamanders (Ambystoma tigrinum) present, and lacking fish. Multispecies reproduc-tive success was best in ponds with lower total nitrogen concentrations, less emergent vegetation, and lacking fish. Habitat factors associated with higher reproductive success varied among individual species. We conclude that small, constructed farm ponds, properly managed, may help sustain amphibian populations in landscapes where natural wetland habitat is rare. We recommend management actions such as limiting livestock access to the pond to improve water quality, reducing nitrogen input, and avoiding the introduction of fish.
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The potential for nitrate to affect amphibian survival was evaluated by examining the areas in North America where concentrations of nitrate in water occur above amphibian toxicity thresholds. Nitrogen pollution from anthropogenic sources enters bodies of water through agricultural runoff or percolation associated with nitrogen fertilization, livestock, precipitation, and effluents from industrial and human wastes. Environmental concentrations of nitrate in watersheds throughout North America range from < 1 to > 100 mg/L. Of the 8,545 water quality samples collected from states and provinces bordering the Great Lakes, 19.8% contained nitrate concentrations exceeding those which can cause sublethal effects in amphibians. In the laboratory lethal and sublethal effects in amphibians are detected at nitrate concentrations between 2.5 and 100 mg/L. Furthermore, amphibian prey such as insects and predators of amphibians such as fish are also sensitive to these elevated levels of nitrate. From this we conclude that nitrate concentrations in some watersheds in North America are high enough to cause death and developmental anomalies in amphibians and impact other animals in aquatic ecosystems. In some situations, the use of vegetated buffer strips adjacent to water courses can reduce nitrogen contamination of surface waters. Ultimately, there is a need to reduce runoff, sewage effluent discharge, and the use of fertilizers, and to establish and enforce water quality guidelines for nitrate for the protection of aquatic organisms. Images Figure 1 Figure 2
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Native trout species, such as the redband trout (Oncorhynchus mykiss), occupy thermally harsh stream habitats in hot, arid rangeland basins of the western United States. Declines in the distribution and abundance of these species has generated interest in understanding how these cold water species survive in these systems, as well as in identifying opportunities to restore these species to their former ranges. The purpose of this study was to assess the potential for thermal stratification to provide thermal refuge for redband trout in stream pools characterized by warm intermittent flow conditions on arid rangelands. We studied vertical thermal stratification in two pools during three summers on Boles Creek located on the Modoc Plateau in extreme northeastern California. Water and air temperature data were collected on a 0.5 h time step from 15-Jun through 15-Sep during 1996, 1997, and 2000 using commercial temperature data-loggers. Water temperature was measured at the top (0.3 m below pool surface) and bottom (0.3 m above pool substrates) of each pool. Vertical thermal stratification occurred within these pools creating conditions as much as 7.6 C cooler and consistently more constant at the bottom of pools compared to pool surface waters. Thermal stratification was dependent upon air temperature with the magnitude of stratification increasing as air temperature increased. The magnitude of thermal stratification varied significantly from year to year, likely reflecting variation in annual weather conditions. The thermal regime in the study pools was often near the upper lethal limit reported for redband trout, but temperatures at the bottom of these pools did offer refuge from lethal temperatures realized near the pool surface. Temperatures at pool bottom were consistently above optimal levels published for redbands.
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Baseline information on water table fluctuation patterns was collected at Sagehen Creek Field Station, near Truckee, California, from June 1987 through November 1989. Relationships between plant community types and water table patterns were examined. Water table patterns were determined from bimonthly measurements of piezometers. Species composition was determined using a 10-point frame placed randomly near each piezometer. Four distinctive water table patterns were identified based on examination of specific water table variables during 2 growing seasons. Five plant community types were identified, designated Deschampsia caespitosa/Carex nebrascensis, Poa pratensis/Potentilla gracilis, Poa pratensis/Carex, Carex angustata/Poa pratensis and Carex angustata. These plant communities were related to specific water table patterns. The D. caespitosa/C. nebrascensis type experienced the greatest annual fluctuation in water table of any of the types. The P. pratensis/Carex plant community type occupied sites with the smallest water table fluctuation. Water table patterns associated with the P. pratensis/Potentilla gracilis community type indicated dry sites, whereas Carex angustata sites had small overall water table fluctuations and were generally wet to moist sites. The complexity of the physical and biological components of meadow ecosystems was demonstrated, suggesting site variation and changes in meadow species may be predicted by monitoring water table pattern.
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Nitrogen (N) in forest soil extracts and surface waters may be dominantly in organic compounds as dissolved organic nitrogen (DON). Due to various difficulties associated with measuring total N (as TKN) by the Rjeldahl digest, this important vehicle for nutrient movement is rarely monitored. By coupling two relatively new methods and optimizing them for use in soil studies, we developed an alternative method for measuring DON. Analysis of pure compounds and field samples shows that persulfate oxidation combined with conductimetric quantification of nitrate (NO3) provides a highly accurate measure of dissolved N content. With relatively inexpensive equipment and reagents, a single technician can digest and assay over a hundred samples a day. This rapid, simple, and accurate assay may make it possible to routinely monitor DON where it had previously been impractical. This in turn could substantially enhance understanding about the form and quantity of N involved in nutrient fluxes.
Conference Paper
Background/Question/Methods: The Yosemite toad (Anaxyrus [= Bufo] canorus) is a high-elevation species endemic to the central Sierra Nevada that is associated predominantly with wet meadows used for breeding habitat. A. canorus has declined in distribution and abundance throughout its historical range; reasons for the declines are unknown but may be related to disease and habitat modification. The existing Kings River Experimental Watersheds (KREW) project in the Sierra National Forest provides an opportunity to study the effects of timber harvest and underburning on this sensitive species. We monitored meadow conditions, A. canorus demographics, and adult A. canorus movement in up to five breeding meadows in 2006-2012 prior to tree thinning and prescribed fire treatments. Meadow conditions were characterized through groundwater well measurements, surface water mensuration, and water chemistry measurements during the breeding period and throughout the ensuing snow-free months. A. canorus demographics in the meadows were calculated using mark-recapture techniques during the breeding period. Movement and upland terrestrial habitat use were analyzed through radio-tracking of adult A. canorus as they left the breeding areas. Results/Conclusions: A. canorus breeding populations were small, with less than an estimated 20 adult males in each study meadow and similar counts of adult females. Results suggest that abundances in several meadows are declining, although numbers of males in one meadow may be increasing. Study meadows had acidic groundwater with annual averages ranging from pH 5.5 to 6.1. Electrical conductivity, a measure of inorganic dissolved solids in water, was low with averages between 20 and 35 µS/cm. Water depths in breeding areas were very shallow with medians generally less than 2 cm and most maximums less than 10 cm. Survival of eggs and larvae to metamorphosis was related to surface water duration. After breeding, adult A. canorus moved a mean distance of 270 m from aquatic breeding sites and made extensive use of terrestrial environments in the mixed-conifer forest. Occupied terrestrial sites had less canopy cover and fewer woody species than unoccupied sites. Adult toads showed site fidelity to both aquatic breeding sites and upland terrestrial areas. These findings will be compared to the data being collected during and after the tree thinning and prescribed fire treatments, which were implemented starting in the late summer of 2012.
Article
In the 1970s we studied habitat use and reproductive biology in Yosemite Toads (Bufo canorus) in the Sierra Nevada Mountains of California. Our surveys of four zones of terrestrial habitat in the post-breeding period provided a sample of 654 toads and revealed population and gender differences in distribution. Wet-meadow bottoms containing breeding pools were occupied by the majority (immatures and adults combined = 58%). Interestingly, the next most occupied zone was at the highest part of the meadow environment where it contacted talus slopes, more than 800 m from the nearest breeding pools (immature and adults combined = 26%). Adult females tended to be located there (108 of 237; 46%), but not adult males (7 of 225; 3%). Ovaries of post-breeding females were only partially developed before they entered hibernation. This suggests that storing enough energy during the brief high altitude summer to provide for both hibernation and reproduction in successive years is difficult and may cause irregular breeding in B. canorus, especially in females because they invest more than males in gonadal mass. We hypothesize that this asymmetry in energy requirements of adults may be the fundamental cause of differential dispersal.
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An ammonia determination based on formation of a substituted indophenol with sodium salicylate as phenolic reagent has been developed and compared with other methods. Sensitivity and reproducibility are comparable with results obtained in a method where phenol was used, while a number of the disadvantages inherent to the use of phenol are avoided. The salicylate method is specific for NH3N and interferences are generally absent in samples from natural fresh waters. The method can be easily applied for seawater analysis.
Article
Frogs are in decline worldwide, and are known to be sensitive indicators of environmental change. Floodplains of the Murray-Darling Basin in southeastern Australia have been altered in many ways by livestock grazing, by the introduction of exotic fish, and by changes to flooding regimes. These changes have led to declines in wetland condition and hence to the availability of habitat for wetland frogs. This study examined relationships between frogs, wetland condition and livestock grazing intensity at 26 wetlands on the floodplain of the Murrumbidgee River. Frog communities, species richness, and some individual species of frogs declined with increased grazing intensity. Wetland condition also declined with increased grazing intensity, particularly the aquatic vegetation and water quality components. There were clear relationships between frog communities and wetland condition, with several taxa responding to aquatic and fringing vegetation components of wetland condition. Thus, grazing intensity appeared to influence frog communities through changes in wetland habitat quality, particularly the vegetation. Reduced stocking rates may result in improved wetland condition and more diverse frog communities. River management to provide natural seasonal inundation of floodplain wetlands may also enhance wetland condition, frog activity and reproductive success.
Article
There has been much concern about widespread declines among amphibians, but efforts to determine the extent and magnitude of these declines have been hampered by scarcity of comparative inventory data. We resurveyed a transect of the Sierra Nevada mountains in western North America that was carefully studied in the early 1990s. Our comparisons show that at least five of the seven frog and toad species in the area have suffered serious declines. One species has disappeared from the area entirely and a second species, formerly the most abundant amphibian in the area, has dwindled to a few small remnant populations. These declines have occurred in a relatively undisturbed, protected area and show some of the same patterns noted in other reports of amphibian declines. Introduced predatory fish, possibly interacting with drought-induced loss of refuge habitats, have contributed to the decline of some species. However, the overall cause of these dramatic losses remains unknown.
Article
Habitat selection in adult and juvenile Bufo achalensis was studied at La Ciénaga Stream, Pampa de Achala, Central Argentina from December 1998 to October 2001. Habitat preference was evaluated by comparing the observed use of each habitat type with its availability. Juveniles were surveyed on 32 occasions between January 1999 and March 2001 using 13 permanent transects. The effect of cattle on larval survivorship was also evaluated. Most adult and juvenile B. achalensis occurred within 300 m of each side of the breeding site stream. No correlation was found between body size and distances moved. Juveniles and adults selected granite outcrops after the breeding season and avoided the heavily grazed areas. Adults also selected the stream and used tall tussock grassland in proportion to its availability. Juveniles used loose, flat, relatively small stones as shelters whilst adults used larger rocks. The presence of cattle at the breeding sites directly reduced larval survivorship by trampling, and indirectly through sediment deposition at the breeding sites resulting from increased stream bank erosion. The habitat preferences of B. achalensis suggest that long term cattle grazing also affects them adversely through deterioration of their transition habitat from tall tussock grassland to short sward. Future conservation management plans for B. achalensis must include the protection of the breeding sites and the surrounding terrestrial area if they are to be effective.
Article
Abstract A study of frog species richness and abundance at four permanent billabongs located in and around the city of Wagga Wagga, southern New South Wales, was carried out from the spring of 1991 to the autumn of 1992. During the sampling period a total of 404 individual adult frogs from six species were recorded. No egg masses or tadpoles were detected during a total of 32 survey hours. Four species of the Family Myobatrachidae represented 81% of the total number of adult individuals sampled, the remaining species belonging to the Family Hylidae. There were significant differences in the mean species richness and mean total number of adult individuals among billabongs. Significant positive correlations were recorded between total adult individuals, total frog species richness and the number of riparian plant species recorded at all billabongs. There were no significant correlations between adult frog numbers and meteorological and water quality parameters. The adults of the four most abundant frog species exhibited significant association with particular microhabitats surrounding billabongs; Crinia parinsignifera was associated with the creeping grass Paspalum distichum, Limnodynastes fletcheri with the rush Eleocharis sphacelata, L. tasmaniensis with sedges Cyperus spp. and the grass P. distichum and Litoria peronii with red gum Eucalyptus camaldulensis and introduced tree species. Differences in adult frog abundance between billabongs appears to be related to the disturbance of riparian vegetation by domestic stock, while the absence of eggs and tadpoles from these permanent billabongs may be explained by the presence of abundant exotic fish species in the billabongs.
Article
ABSTRACT Global amphibian declines have been linked to various anthropogenic land uses. Recent studies have documented negative impacts of cropland agriculture and deforestation on amphibians; however, few have examined potential impacts of cattle grazing in wetlands on resident amphibians. Therefore, we measured differences in number of captures and body size of postmetamorphic amphibians, egg mass abundance, and shoreline vegetation structure and composition between 4 wetlands with direct cattle access and 4 wetlands from which cattle were excluded on the Cumberland Plateau in Tennessee, USA. We captured amphibians at wetlands from March to August 2005 and 2006 using pitfall traps. Number of green frog (Rana clamitans) metamorphs captured at nonaccess wetlands was 2.5 times and 9.8 times greater than at wetlands with cattle access in 2005 and 2006, respectively. However, number of American toads (Bufo americanus) captured was 68 times and 76 times greater at cattle-access wetlands in 2005 and 2006, respectively. In general, metamorph body size was negatively correlated with species-specific capture rate. We detected no differences in egg mass abundance between cattle land-use types. Height, percent horizontal cover, and percent vertical cover of shoreline vegetation were 74%,25%, and 84% greater, respectively, in nonaccess wetlands in 2005; vegetation trends were similar in 2006. Our results suggest that cattle impact amphibian populations but effects vary by species. Differences in postmetamorphic capture rate may be related to less emergent vegetation at cattle-access wetlands. Although body size differed between land uses for metamorphs, these trends probably were short-lived, because we did not detect differences in juvenile and adult body size between land uses for most species. Based on our findings, we suggest that fencing cattle from wetlands may be a prudent conservation strategy for some amphibian species (e.g., ranids), whereas other species (e.g., bufonids) may benefit from controlled grazing.
Article
Leopard frog (Rana pipiens), green frog (Rana clamitans), and American toad (Bufo americanus) embryos were exposed to different un-ionized ammonia (NH3) levels over an ecologically relevant range (0–2 mg NH3/L H2O). Hatching success and prevalence of deformities were recorded after acute exposures (3–5 d duration) at 23°C and pH 8.7. Green frog tadpoles were exposed to different NH3 levels in a subchronic experiment (114 d), and growth, survival, and metamorphosis were monitored. Survival declined, the prevalence of deformities increased, and growth and development were slow in anuran embryos and tadpoles exposed to NH3 concentrations in excess of 0.6 mg/L (green frogs) or 1.5 mg/L (leopard frogs). No effects were observed in American toads up to a concentration of 0.9 mg/L NH3. It appears from the few data available that anurans may not be particularly sensitive to NH3 when compared with many fish species and that water quality criteria determined using data collected on fish species will be protective for many anuran amphibians. The NH3 concentrations that caused negative effects in these experiments are higher than measured values for water in the Fox River–Green Bay ecosystem (WI, USA) but lower than for pore sediment water. In this ecosystem, anuran amphibians are potentially exposed to hazardous levels of NH3 when they hibernate on the bottom or buried in sediments or during episodic releases of NH3 from sediments.
Article
In static experiments, we studied the effects of nitrate and nitrite solutions on newly hatched larvae of five species of amphibians, namely Rana pretiosa, Rana aurora, Bufo boreas, Hyla regilla, and Ambystoma gracile. When nitrate or nitrite ions were added to the water, some larvae of some species reduced feeding activity, swam less vigorously, showed disequilibrium and paralysis, suffered abnormalities and edemas, and eventually died. The observed effects increased with both concentration and time, and there were significant differences in sensitivity among species. Ambrystoma gracile displayed the highest acute effect in water with nitrate and nitrite. The three ranid species had acute effects in water with nitrite. In chronic exposures, R. pretiosa was the most sensitive species to nitrates and nitrites. All species showed 15-d LC50s lower than 2 mg N-NO2-/L. For both N ions, B. boreas was the least sensitive amphibian. All species showed a high mortality at the U.S. Environmental Protection Agency-recommended limits of nitrite for warm-water fishes (5 mg N-NO2-/L) and a significant larval mortality at the recommended limits of nitrite concentration for drinking water (1 mg N-NO2-/L). The recommended levels of nitrate for warm-water fishes (90 mg N-NO3-/L) were highly toxic for R. pretiosa and A. gracile larvae.
Article
Wind-borne pesticides have long been suggested as a cause of amphibian declines in areas without obvious habitat destruction. In California, the transport and deposition of pesticides from the agriculturally intensive Central Valley to the adjacent Sierra Nevada is well documented, and pesticides have been found in the bodies of Sierra frogs. Pesticides are therefore a plausible cause of declines, but to date no direct links have been found between pesticides and actual amphibian population declines. Using a geographic information system, we constructed maps of the spatial pattern of declines for eight declining California amphibian taxa, and compared the observed patterns of decline to those predicted by hypotheses of wind-borne pesticides, habitat destruction, ultraviolet radiation, and climate change. In four species, we found a strong positive association between declines and the amount of upwind agricultural land use, suggesting that wind-borne pesticides may be an important factor in declines. For two other species, declines were strongly associated with local urban and agricultural land use, consistent with the habitat-destruction hypothesis. The patterns of decline were not consistent with either the ultraviolet radiation or climate-change hypotheses for any of the species we examined.
Article
SUMMARY 1. Agricultural practices such as cattle farming may have direct or indirect negative effects on larval amphibians by decreasing water quality through deposition of nitrogenous waste, causing eutrophication, and grazing shoreline vegetation that contributes to detrital cover and food. 2. We sampled amphibian larvae on the Cumberland Plateau, Tennessee, U.S.A., twice per week, water quality twice per month and algal and detrital biomass once per month at seven wetlands (three cattle-access and four non-access) from March to August 2005 and 2006. 3. In general, species richness and diversity of amphibian larvae were greater in wetlands without cattle. Mean relative abundance of green frog (Ranaclamitans) and American bullfrog (Rana catesbeiana) tadpoles was greater in non-access wetlands. Body size of some ranid larvae was larger in cattle-access wetlands but this trend did not exist for juveniles or adults. Dissolved oxygen was lower, while specific conductivity and turbidity were higher in cattle-access wetlands. Mean biomass of detritus was lower in cattle-access wetlands compared to non-access wetlands; no differences were detected in algal biomass. 4. Given the negative impacts of cattle on water quality, detrital biomass, larval amphibian species richness and relative abundance of some amphibian species, we recommend that farmers consider excluding these livestock from aquatic environments.
Book
Linear Mixed-Effects * Theory and Computational Methods for LME Models * Structure of Grouped Data * Fitting LME Models * Extending the Basic LME Model * Nonlinear Mixed-Effects * Theory and Computational Methods for NLME Models * Fitting NLME Models
Book
This text is a Stata-specific treatment of generalized linear mixed models, also known as multilevel or hierarchical models. These models are "mixed" in the sense that they allow fixed and random effects and are "generalized" in the sense that they are appropriate not only for continuous Gaussian responses but also for binary, count, and other types of limited dependent variables.
Determining the effects of livestock grazing on Yosemite toads (Bufo canorus) and their habitat: final report to USDA Forest Service Region 5 45 p
  • Allen
  • B Diaz
  • S K Mcilroy
  • L M Roche
  • K W Tate
Allen-Diaz, B., S. K. MCILROY, L. M. ROCHE, K. W. TATE, and A. J. LIND. 2010. Determining the effects of livestock grazing on Yosemite toads (Bufo canorus) and their habitat: final report to USDA Forest Service Region 5 45 p. Vallejo, CA, USA : US Department of Agriculture Forest Service.
Montane and subalpine vegetation in the Sierra Nevada Terrestrial vegetation of California
  • Fites
  • J A Kaufman
  • P Rundel
  • N Stephenson
  • D A Weixelman
Fites-Kaufman, J. A., P. Rundel, N. Stephenson, and D. A. Weixelman. 2007. Montane and subalpine vegetation in the Sierra Nevada. In: M. G. Barbour, T. Keeler-Wolf, and A. A. Schoenherr [eds.]. Terrestrial vegetation of California. Berkeley, CA, USA : University of California Press. p. 456-493.
Utilization studies and residual measurements. Denver, CO, USA : US Department of the Interior, Bureau of Land Management–National Applied Resources Science Center , Interagency Technical Reference
  • [ Itt Interagency
  • Team
[ITT] Interagency Technical Team. 1996. Utilization studies and residual measurements. Denver, CO, USA : US Department of the Interior, Bureau of Land Management–National Applied Resources Science Center , Interagency Technical Reference, Report BLM/RS/ST-96/004. 164 p.
Status of amphibians In: Status of the Sierra Nevada, Sierra Nevada ecosystem project: final report to Congress. Volume 2
  • M R Jennings
Jennings, M. R. 1996. Status of amphibians. In: Status of the Sierra Nevada, Sierra Nevada ecosystem project: final report to Congress. Volume 2. Davis, CA, USA : Center for Water and Wildland Resources, University of California, Davis. p. 921-944.
Amphibian and reptile species of special concern in California. Final report to California Department of Fish and Game, Inland Fisheries Division
  • M R Jennings
  • M P Hayes
Jennings, M. R., and M. P. Hayes. 1994. Amphibian and reptile species of special concern in California. Final report to California Department of Fish and Game, Inland Fisheries Division. Rancho Cordova, CA, USA: California Department of Fish and Game. 255 p.
Riparian areas and wetlands
  • R Kattleman
  • M Embury
Kattleman, R., and M. Embury. 1996. Riparian areas and wetlands. Davis, CA, USA : Center for Water and Wildland Resources, University of California, Davis. p. 201-267.
Decline, movement and habitat utilization of the Yosemite toad (Bufo canorus): an endangered anuran endemic to the Sierra Nevada of California
  • D W Martin
Martin, D. W. 2008. Decline, movement and habitat utilization of the Yosemite toad (Bufo canorus): an endangered anuran endemic to the Sierra Nevada of California. Santa Barbara, CA, USA : University of California. 406 p.
Identifying ecological patterns and processes in montane meadows of the Sierra Nevada range [PhD dissertation]
  • S K Mcilroy
McIlroy, S. K. 2008. Identifying ecological patterns and processes in montane meadows of the Sierra Nevada range [PhD dissertation]. Berkeley, CA, USA : University of California, Berkeley. 117 p.
Meadows in the Sierra Nevada of California: state of knowledge : US Department of Agriculture Forest Service General Technical Report PSW-84
  • R Ratliff
Ratliff, R. 1985. Meadows in the Sierra Nevada of California: state of knowledge. Berkeley, CA, USA : US Department of Agriculture Forest Service General Technical Report PSW-84. 54 p.
The toad that stays on its toes
  • C K Sherman
  • M L Morton
Sherman, C. K., and M. L. Morton. 1984. The toad that stays on its toes. Natural History 93: 72-78.
Sierra Nevada Forest Plan Amendment: final environmental impact statement and record of decision
  • [ Usda Department
[USDA] US Department of Agriculture. 2001. Sierra Nevada Forest Plan Amendment: final environmental impact statement and record of decision. Vallejo, CA, USA : USDA Forest Service, Pacific Southwest Region.
Endangered and threatened wildlife and plants; 12-month finding for petition to list Yosemite toad
  • [ Usdi Department
[USDI] US Department of the Interior. 2002. Endangered and threatened wildlife and plants; 12-month finding for petition to list Yosemite toad. Federal Register 67(237): 75834-75843.
California's wildlife. Volume I: amphibians and reptiles
  • D C Zeiner
  • W F Laudenslayer
  • K E Mayer
Zeiner, D. C., W. F. Laudenslayer, and K. E. Mayer. 1988. California's wildlife. Volume I: amphibians and reptiles. Sacramento, CA, USA : California Department of Fish and Game. 272 p.
associated with billabong habitats on the Murrumbidgee floodplain, Australia Utilization studies and residual measure-ments
  • M Healey
HEALEY, M., D. THOMPSON, associated with billabong habitats on the Murrumbidgee floodplain, Australia. Australian Journal of Ecology 22:270–278. [ITT] INTERAGENCY TECHNICAL TEAM. 1996. Utilization studies and residual measure-ments. Denver, CO, USA: US Department of the Interior, Bureau of Land Management–National Applied Resources Science Center, Interagency Technical Reference, Report BLM/RS/ST-96/004. 164 p
Utilization studies and residual measurements
  • Itt
  • Interagency
  • Team
[ITT] INTERAGENCY TECHNICAL TEAM. 1996. Utilization studies and residual measurements. Denver, CO, USA: US Department of the Interior, Bureau of Land Management–National Applied Resources Science Center, Interagency Technical Reference, Report BLM/RS/ST-96/004. 164 p.
Endangered and threatened wildlife and plants; review of species that are candidates or proposed for listing as endangered or threatened; annual notice of findings on resubmitted petitions; annual description of progress on listing actions
USDI. 2004. Endangered and threatened wildlife and plants; review of species that are candidates or proposed for listing as endangered or threatened; annual notice of findings on resubmitted petitions; annual description of progress on listing actions. Federal Register 69(86):25876–24904.