Geology topics

Research about Rocky Mountain National Park

Source-linked reports with geographic coverage including Rocky Mountain National Park.

At least 37 records · Page 2Linked to original sources

USGS2013

Evaluation of National Atmospheric Deposition Program measurements for co-located Sites CO89 and CO98 at Rocky Mountain National Park, 2012

Atmospheric wet-deposition monitoring in Rocky Mountain National Park included precipitation depth and aqueous chemical measurements at co-located National Atmospheric Deposition Program (NADP) sites CO89 and CO98 (Loch Vale) during 2012. The co-located sites are separated by approximately 6.5 meters horizontally and 0.5 meters in altitude, which meets NADP siting criteria. Median weekly absolute percent differences for selected parameters including: sample volume, 8.0 percent; ammonium concentration, 9.1 percent; nitrate concentration, 8.5 percent; sulfate concentration, 10.2 percent. Annual precipitation-weighted mean concentrations were higher for CO98 compared to CO89 for all analytes. The chemical concentration record for CO98 contains more valid samples than the CO89 record. Therefore, the CO98 record is more representative of 2012 total annual deposition at Loch Vale. Daily precipitation-depth records for the co-located precipitation gages were 100 percent complete, and the total annual precipitation depths between the sites differed by 0.1 percent for the year (91.5 and 91.4 cm).

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USGS2012

The genetic structure of a relict population of wood frogs

Habitat fragmentation and the associated reduction in connectivity between habitat patches are commonly cited causes of genetic differentiation and reduced genetic variation in animal populations. We used eight microsatellite markers to investigate genetic structure and levels of genetic diversity in a relict population of wood frogs ( Lithobates sylvatica ) in Rocky Mountain National Park, Colorado, where recent disturbances have altered hydrologic processes and fragmented amphibian habitat. We also estimated migration rates among subpopulations, tested for a pattern of isolation-by-distance, and looked for evidence of a recent population bottleneck. The results from the clustering algorithm in Program STRUCTURE indicated the population is partitioned into two genetic clusters (subpopulations), and this result was further supported by factorial component analysis. In addition, an estimate of FST (FST = 0.0675, P value \0.0001) supported the genetic differentiation of the two clusters. Estimates of migration rates among the two subpopulations were low, as were estimates of genetic variability. Conservation of the population of wood frogs may be improved by increasing the spatial distribution of the population and improving gene flow between the subpopulations. Construction or restoration of wetlands in the landscape between the clusters has the potential to address each of these objectives.

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USGS2011

Monitoring plan for vegetation responses to elk management in Rocky Mountain National Park

Rocky Mountain National Park (RMNP) in north-central Colorado supports numerous species of wildlife, including several large ungulate species among which Rocky Mountain elk (Cervus elaphus) are the most abundant. Elk are native to RMNP but were extirpated from the area by the late 1800s. They were reintroduced to the area in 1913-1914, and the elk herd grew to the point that it was actively managed from 1944 until 1968. In 1969, the active control of elk was discontinued and since then the herd has increased to a high point ranging from 2,800 to 3,500 between 1997 and 2001. In recent years, there has been growing concern over the condition of vegetation in the park and conflicts between elk and humans, both inside and outside the park. In response to these concerns, RMNP implemented an Elk and Vegetation Management Plan (EVMP) in 2009 to guide management actions in the park over a 20-year time period with the goal of reducing the impacts of elk on vegetation and restoring the natural range of variability in the elk population and affected plant and animal communities. The EVMP outlines the desired future condition for three vegetation communities where the majority of elk herbivory impacts are being observed: aspen, montane riparian willow, and upland herbaceous communities. The EVMP incorporates the principle of adaptive management whereby the effectiveness of management actions is assessed and adjusted as needed to successfully achieve objectives. Determination of whether vegetation objectives are being achieved requires monitoring and evaluation of target vegetation communities. The current report describes the design and implementation of a vegetation-monitoring program to help RMNP managers assess the effectiveness of their management actions and determine when and where to alter actions to achieve the EVMP's vegetation objectives. This monitoring plan details the process of selecting variables to be monitored, overall sampling design and structure, site selection, data collection methods, and statistical analyses to be used to conduct this monitoring program in conjunction with the EVMP. We report the baseline conditions observed at the time of the establishment of monitoring sites. We include detailed field protocols for site establishment and data collection, as well as timetables for sampling, so that RMNP staff will be able to continue monitoring the sites established during this implementation stage, and continue to add new sites when necessary, as the execution of the EVMP proceeds over the next 20 years.

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USGS2010

Chemical weathering in the Loch Vale Watershed, Rocky Mountain National Park, Colorado

Mineralogic, hydrologic, and geochemical data were used to determine the source of solutes to surface waters draining the Loch Vale Watershed (LVWS), an alpine-subalpine drainage located in the Front Range of Colorado. The flux of dissolved solids from LVWS is primarily controlled by interactions between snowmelt and materials derived from the local bedrock; the biomass has only a minor effect on solute budgets except for ammonium. LVWS is underlain by Precambrian granite and gneiss, the major minerals include quartz, microcline, plagioclase, biotite, and sillimanite. Small amounts of calcite were found along hydrothermally altered zones in the bedrock. Mass balance calculations indicate that the weathering of calcite contributes nearly 40% of the cations derived within the basin. The importance of calcite weathering in LVWS is a result of its chemical reactivity and the high rate of physical erosion in this alpine environment. The average cationic denudation rate in the drainage (390 eq/ha/yr) is similar to long-term rates in forested Adirondack watersheds (500–600 eq/ha/yr), but much lower than the average for the North American Continent (3800 eq/ha/yr). Surface waters in LVWS are susceptible to acidification should acid deposition from the atmosphere increase.

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USGS2007

Species-area curves indicate the importance of habitats' contributions to regional biodiversity

We examined species-area curves, species composition and similarity (Jaccard's coefficients), and species richness in 17 vegetation types to develop a composite index of a vegetation type's contribution to regional species richness. We collected data from 1 to 1000 m2 scales in 147 nested plots in Rocky Mountain National Park, Colorado, USA to compare three species-area curve models' abilities to estimate the number of species observed in each vegetation type. The log(species)-log(area) curve had the largest adjusted coefficients of determination (r2 values) in 12 of the 17 types, followed by the species-log(area) curve with five of the highest values. When the slopes of the curves were corrected for species overlap among plots with Jaccard's coefficients, the species-log(area) curves estimated values closest to those observed. We combined information from species-area curves and measures of heterogeneity with information on the area covered by each vegetation type and found that the types making the greatest contributions to regional biodiversity covered the smallest areas. This approach may provide an accurate and relatively rapid way to rank hotspots of plant diversity within regions of interest.

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USGS2006

Estimation of temporary emigration in male toads

Male boreal toads (Bufo boreas) are thought to return to the breeding site every year but, if absent in a particular year, will be more likely to return the following year. Using Pollock's robust design we estimated temporary emigration (the probability a male toad is absent from a breeding site in a given year) at three locations in Colorado, USA: two in Rocky Mountain National Park and one in Chaffee County. We present data that suggest that not all male toads return to the breeding site every year. Our analyses indicate that temporary emigration varies by site and time (for example, from 1992 to 1998, the probability of temporary emigration ranged from 10% to 29% and from 3% to 95% at Lost Lake and Kettle Tarn, respectively). Although the results provide weak evidence that males are more likely to return after a year's hiatus, a general pattern of state-dependent temporary emigration was not supported. We also hypothesized relationships between temporary emigration and a number of weather variables. While some competitive models included weather covariates, imprecise and variable estimates of the effects of these covariates precluded fully defining their impact on temporary emigration. ?? 2006 by the Ecological Society of America.

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USGS2006

Alpine plant community trends on the elk summer range of Rocky Mountain National Park, Colorado: An analysis of existing data

The majority of the elk (Cervus elaphus) population of Rocky Mountain National Park in Colorado summer in the park’s high-elevation alpine and subalpine meadows and willow krummholz. The park’s population of white-tailed ptarmigan (Lagopus leucurus altipetens) depends on both dwarf and krummholz willows for food and cover. Concern about the effects of elk herbivory on these communities prompted the monitoring of 12 vegetation transects in these regions from 1971 to 1996. Over this 25-year period, data were collected on plant species cover and frequency and shrub heights. These data have not been statistically analyzed for trends in the measured variables over time to determine changes in species abundance. Krummholz willow species (Salix planifolia, S. brachycarpa) declined 17–20 percent in cover and about 25 centimeters in height over the study period. Graminoids (particularly Deschampsia caespitosa, Carex, and Poa) increased slightly from 1971 to 1996. No significant increases of nonnative plant species were observed. An increase in presence of bare ground over the 25-year period warrants continued measurement of these transects. Lack of good data on elk density, distribution, or use levels precludes correlating changes in plant species cover, frequency, or heights with elk population trends. I recommend development of a more rigorously designed monitoring program that includes these transects as well as others chosen on a random or stratified design and consistent measurement protocol and sampling intervals. Some method of quantifying elk use, either through measurement of plant utilization, pellet counts, or census-type surveys, would allow correlation of changes in plant species over time with changes in elk distribution and density on the park’s alpine and subalpine regions.

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USGS2004

Effects of elk herbivory on vegetation and nitrogen processes

We used 35-year and 4-year ungulate exclosures to determine the effects of elk ( Cervus elaphus ) herbivory on above-ground and below-ground production and soil fertility on the elk winter range in Rocky Mountain National Park (RMNP), Colorado, USA. We used paired grazed and ungrazed plots to evaluate ungulate herbivory effects in short and tall willow ( Salix spp.), aspen ( Populus spp.), and upland grass/shrub vegetation associations. We measured nitrogen (N) fluxes (litter deposition, fecal and urinary deposition from elk, movements of N by elk, N mineralization, soil N availability, elk consumption rates) within the elk winter, above-ground and below-ground N pools (herbaceous, shrub and root biomass, %N in plants, roots, and soil), and N fluxes on and off the elk winter range (seasonal movement of N by elk). Nitrogen mineralization and soil nitrate (NO 3 ) pools were reduced in the short willow community ( P = 0.07 and 0.10, respectively; n = 4 sites) in grazed plots, but not in the upland grass/shrub community or tall willow sites ( P >0.10). Annual growth of willows was reduced by 98% in grazed plots, relative to 35-year exclosures, and 66% relative to 4-year exclosures. Thus, height, canopy size, and litter biomass of willows were reduced, and N yield of willows was 64% less in grazed plots. We evaluated movement of N by elk among 6 major vegetation associations and found that elk grazed more and bedded less in willow vegetation association compared to mixed conifer, mesic meadow, and grassland/shrub associations ( P = 0.014, 0.001, and 0.026, respectively), suggesting that elk herbivory and movement led to a net loss of N in the willow vegetation association. Elk spent less total time in willows than mesic meadow association, yet they consumed large amounts of willow plant biomass. We recommend management of elk numbers and elk herbivory that takes into consideration impacts to N process function, as negative effects from current levels of herbivory were observed in ≥1 of 3 vegetation associations studied.

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USGS2003

Atmospheric deposition of nutrients, pesticides, and mercury in Rocky Mountain National Park, Colorado, 2002

Nutrients, current-use pesticides, and mercury were measured in atmospheric deposition during summer in Rocky Mountain National Park in Colorado to improve understanding of the type and magnitude of atmospheric contaminants being deposited in the park. Two deposition sites were established on the east side of the park: one at an elevation of 2,902 meters near Bear Lake for nutrients and pesticides, and one at an elevation of 3,159 meters in the Loch Vale watershed for mercury. Concentrations of nutrients in summer precipitation at Bear Lake ranged from less than 0.007 to 1.29 mg N/L (milligrams of nitrogen per liter) for ammonium and 0.17 to 4.59 mg N/L for nitrate and were similar to those measured at the Loch Vale National Atmospheric Deposition Network station, where nitrogen concentrations in precipitation are among the highest in the Rocky Mountains. Atrazine, dacthal, and carbaryl were the most frequently detected pesticides at Bear Lake, with carbaryl present at the highest concentrations (0.0079 to 0.0952 ?g/L (micrograms per liter), followed by atrazine (less than 0.0070 to 0.0604 ?g/L), and dacthal (0.0030 to 0.0093 ?g/L). Mercury was detected in weekly bulk deposition samples from Loch Vale in concentrations ranging from 2.6 to 36.2 ng/L (nanograms per liter). Concentrations in summer precipitation were combined with snowpack data from a separate study to estimate annual deposition rates of these contaminants in 2002. Annual bulk nitrogen deposition in 2002 was 2.28 kg N/ha (kilograms of nitrogen per hectare) at Bear Lake and 3.35 kg N/ha at Loch Vale. Comparison of wet and bulk deposition indicated that dry deposition may account for as much as 28 percent of annual nitrogen deposition, most of which was deposited during the summer months. Annual deposition rates for three pesticides were estimated as 45.8 mg/ha (milligrams per hectare) of atrazine, 14.2 mg/ha of dacthal, and 54.8 mg/ha of carbaryl. Because of much higher pesticide concentrations in summer precipitation than in winter snow, between 80 to 90 percent of the annual pesticide deposition occurs during summer. Mercury deposition to Loch Vale was estimated at 7.1 ?g/m2 (micrograms per square meter) of which nearly 70 percent of the annual mercury deposition occurred during summer. Despite the fact that most precipitation at high-elevations falls during winter, these results emphasize the importance of monitoring precipitation chemistry during summer to improve estimates of contaminant deposition to high-elevation ecosystems in Rocky Mountain National Park. Air-parcel back trajectories were calculated using an atmospheric transport model to identify potential source regions for contaminants reaching the park. The results indicate that during the winter, the most likely source of contami-nants is from areas northwest of the park, but during summer, contaminants are most likely coming from sources to the southwest and east.

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USGS2003

Beaver (Castor canadensis) in heavily browsed environments

Beaver ( Castor canadensis ) populations have declined or failed to recover in heavily browsed environments. I suggest that intense browsing by livestock or ungulates can disrupt beaver-willow ( Salix spp.) mutualisms that likely evolved under relatively low herbivory in a more predator-rich environment, and that this interaction may explain beaver and willow declines. Field experiments in Rocky Mountain National Park, Colorado, USA, found the interaction of beaver and elk ( Cervus elaphus ) herbivory suppressed compensatory growth in willow. Intense elk browsing of simulated beaver-cut willow produced plants which were small and hedged with a high percentage of dead stems, whereas protected plants were large and highly branched with a low percentage of dead stems. Evaluation of a winter food cache showed beaver had selected woody stems with a lower percentage of leaders browsed by elk. A lack of willow stems suitable as winter beaver food may cause beaver populations to decline, creating a negative feedback mechanism for beaver and willow. In contrast, if browsing by livestock or ungulates can be controlled, and beaver can disperse from a nearby source population, then beaver may build dams in marginal habitat which will benefit willow and cause a positive riparian response that restores proper function to degraded habitat. In a shrub-steppe riparian ecosystem of northwestern Colorado, USA, rest from overgrazing of livestock released herbaceous vegetation initiating restoration of a beaver-willow community. Thus, competition from livestock or ungulates can cause beaver and willow to decline and can prevent their restoration in heavily browsed riparian environments, but beaver and willow populations can recover under proper grazing management.

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USGS2002

Influences of herbivory and water on willow in elk winter range

Elimination of large predators and reduced hunter harvest have led to concerns that an increasing elk ( Cervus elaphus ) population may be adversely affecting vegetation on the low-elevation elk winter range of Rocky Mountain National Park, Colorado, USA. Beaver ( Castor canadensis ) and their impoundments also have declined dramatically (94%) in the same area over the past 50 years coincident with a 20% decline in willow ( Salix spp.) cover. From 1994 to 1998, we studied vegetation production responses of willow communities to elk herbivory and water availability. We estimated willow production by measuring current annual growth of shrubs in 9.3-m2 circular plots, and we measured herbaceous production by clipping vegetation within 0.25-m2 circular plots. Elk herbivory suppressed willow heights, leader lengths, annual production, and herbaceous productivity of willow communities. Water impoundment had a positive effect on herbaceous plant production, but little effect on shrubs, possibly because water tables were naturally high on the study sites even without beaver dams. Nevertheless, the winter range environment previously included more riparian willow habitat because of more stream area (47-69%) due to larger beaver populations. Elk herbivory appears to be the dominant force determining vegetation productivity in willow sites, but the effects may be exacerbated by lowered water tables. Fewer elk or protection from browsing, and water enhancement for <10 years along with management to encourage elk movement away from willow communities, could possibly work as strategies to reestablish sustainable willow communities.

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USGS2002

Ecological evaluation of the abundance and effects of elk herbivory in Rocky Mountain National Park, Colorado, 1994-1999

Several National Park Service units in the Intermountain region possess a number of closely related management needs relative to the abundance of wild ungulates and their herbivory effects on plants and ecosystem processes. In 1993, the then National Biological Service (NBS) - now U.S. Geological Survey, Biological Resources Discipline (USGS, BRD) initiated a series of research studies in four park units in the Intermountain West., into the abundance and effects of ungulates on park ecosystems. Each of these parks received a number of similar research study elements including: (a) a number of new ungulate grazing exclosures (n = 12-21 exclosures per park); (b) aerial survey sightability models to estimate population sizes of ungulates; (e) measures of biomass production and consumption rates near the exclosures and across the landscape; (d) studies of the effects of the grazing on plant abundance, species diversity, and ecosystem effects; and (e) computer model simulations (SAVANNA) of the effects on the ecosystem and plant resources of different ungulate management scenarios. One park unit, Rocky Mountain National Park, Colorado, received funding from the U.S. Geological Survey (USGS, BRD) and parallel funding from NPS for an intensive research study of the effects of elk on the park ecosystems.

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USGS2001

Rapid assessment of butterfly diversity in a montane landscape

We present the results of a rapid assessment of butterfly diversity in the 754 ha Beaver Meadows study area in Rocky Mountain National Park, Larimer County, Colorado. We measured butterfly species richness and relative abundance as part of a landscape-scale investigation of diversity patterns involving several groups of organisms. A stratified random sampling design was used to include replication in both rare and common vegetation types. We recorded 49 butterfly species from the twenty-four 0.1 ha plots that were sampled four times during June, July, and August 1996. Butterfly species richness, diversity, and uniqueness were highest in quaking aspen ( Populus tremuloides Michaux) groves and wet meadows, which occupy only a small proportion of the studied landscape. This result supports the suggestion that aspen areas represent ‘hotspots’ of biological diversity in this montane landscape. Patterns of butterfly species richness were positively correlated with total vascular plant species richness ( r = 0.69; P < 0.001), and native plant species richness ( r = 0.64; P < 0.001). However, exotic plant species richness ( r = 0.70; P < 0.001) and the cover of exotic plant species ( r = 0.70; P < 0.001) were the best predictors of butterfly species richness.

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USGS2001

Experimental repatriation of boreal toad (Bufo boreas) eggs, metamorphs, and adults in Rocky Mountain National Park

The boreal toad ( Bufo boreas ) is an endangered species in Colorado and is considered a candidate species for federal listing by the United States Fish and Wildlife Service. Boreal toads are absent from many areas of suitable habitat in the Southern Rocky Mountains of Colorado presumably due to a combination of causes. We moved boreal toads from existing populations and from captive rearing facilities to habitat which was historically, but is not currently, occupied by toads to experimentally examine methods of repatriation for this species. Repatriation is defined as the release of individuals into areas currently of historically occupied by that species (Dodd and Seigel, 1991). This effort was in response to one of the criteria for delisting the boreal toad in Colorado stated in the conservation plan and agreement for the management and recovery of the Southern Rocky Mountain population of the boreal toad (Loeffler, 1998:16); "...there must be at least 2 viable breeding populations of boreal toads in each of at least 9 of 11 mountain ranges of its historic distribution." Without moving eggs from established wild populations, or from captivity to historical localities, it is doubtful whether the recovery team will attain this ambitions goal.

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USGS2000

Relations between basin characteristics and stream water chemistry in alpine/subalpine basins in Rocky Mountain National Park, Colorado

Relations between stream water chemistry and topographic, vegetative, and geologic characteristics of basins were evaluated for nine alpine/subalpine basins in Rocky Mountain National Park, Colorado, to identify controlling parameters and to better understand processes governing patterns in stream water chemistry. Fractional amounts of steep slopes (≥30°), unvegetated terrain, and young surficial debris within each basin were positively correlated to each other. These terrain features, which commonly occur on steep valley side slopes underlain by talus, were negatively correlated with concentrations of base cations, silica, and alkalinity and were positively correlated with nitrate, acidity, and runoff. These relations might result from the short residence times of water and limited soil development in the talus environment, which limit chemical weathering and nitrogen uptake. Steep, unvegetated terrains also tend to promote high Ca/Na ratios in stream water, probably because physical weathering rates in those areas are high. Physical weathering exposes fresh bedrock that contains interstitial calcite, which weathers relatively quickly. The fractional amounts of subalpine meadow and, to a lesser extent, old surficial debris in the basins were positively correlated to concentrations of weathering products and were negatively correlated to nitrate and acidity. These relations may reflect more opportunities for silicate weathering and nitrogen uptake in the lower‐energy environments of the valley floor, where soils are finer‐grained, older, and better developed and slopes are relatively flat. These results indicate that in alpine/subalpine basins, slope, vegetation (or lack thereof), and distribution and age of surficial materials are interrelated and can have major effects on stream water chemistry.

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USGS1998

Effects of ultraviolet radiation on boreal toads in Colorado

Field exposures of Bufo boreas embryos to fractions of ambient UV-B radiation at two sites in Rocky Mountain National Park, Colorado, USA, were conducted to evaluate UV-B as a possible cause of recent severe declines of this species. There were no differences in hatching success of B. boreas embryos exposed to 0–100% of ambient UV-B radiation at either study site, results that are different from those of recent studies in Oregon that found increased mortality of B. boreas embryos exposed to ambient UV-B. The reasons for these differing results are not apparent, and several possible explanations exist, including differences in experimental design, presence or absence of a pathogenic fungus, and geographic genetic variation. Bufo boreas embryos were probably not receiving higher doses of UV-B radiation during the experiments in Oregon compared to the experiments in this study. Results of this study do not support UV-B radiation alone as the cause of the decline of B. boreas during the past 20 yr in the southern Rocky Mountains, but UV-B cannot be dismissed because of the contradictory results from other studies.

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USGS1997

Chemical characteristics of particulate, colloidal, and dissolved organic material in Loch Vale Watershed, Rocky Mountain National Park

The chemical relationships among particulate and colloidal organic material and dissolved fulvic acid were examined in an alpine and subalpine lake and two streams in Loch Vale Watershed, Rocky Mountain National Park. The alpine lake, Sky Pond, had the lowest dissolved organic carbon (DOC) (0.37 mgC/L), the highest particulate carbon (POC) (0.13 mgC/L), and high algal biomass. The watershed of Sky Pond is primarily talus slope, and DOC and POC may be autochthonous. Both Andrews Creek and Icy Brook gain DOC as they flow through wet sedge meadows. The subalpine lake, The Loch, receives additional organic material from the surrounding forest and had a higher DOC (0.66 mgC/L). Elemental analysis, stable carbon isotopic compositon, and 13C-NMR characterization showed that: 1) particulate material had relatively high inorganic contents and was heterogeneous in compositon, 2) colloidal material was primarily carbohydrate material with a low inorganic content at all sites; and 3) dissolved fulvic acid varied in compositon among sites. The low concentration and carbohydrate-rich character of the colloidal material suggests that this fraction is labile to microbial degradation and may be turning over more rapidly than particulate fractions or dissolved fulvic acid. Fulvic acid from Andrews Creek had the lowest N content and aromaticity, whereas Sky Pond fulvic acid had a higher N content and lower aromaticity than fulvic acid from The Loch. The UV-visible spectra of the fulvic acids demonstrate that variation in characteristics with sources of organic carbon can explain to some extent the observed nonlinear relationship between UV-B extinction coefficients and DOC concentrations in lakes.

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USGS1997

Survey and assessment of amphibian populations in Rocky Mountain National Park

We conducted surveys in Rocky Mountain National Park, Colorado for amphibians in 1987-1994. Four species, Ambystoma tigrinum, Bufo boreas, Pseudacris maculata, and Rana sylvatica , were recorded. Pseudacris maculata was the most widely distributed and abundant species in the Park. Two populations of E maculata were estimated to contain 161 and 136 breeding males in 1988. There was no evidence of a decline of A. tigrinum or R. sylvatica , but these species were found at relatively few locations. We did not detect Rana pipiens , which had been known previously from 3 locations in the Park. We found 7 breeding populations of B. boreas , which has declined recently elsewhere in the southern Rocky Mountains, but all but 2 of these populations were small and may not reproduce annually. At least one of these small populations is thought to have been extirpated. Estimated numbers of males in the 2 large populations, which are 6.4 km apart in the same drainage, were stable or increasing slightly from 1992 to 1995, averaging 189 and 239 individuals. Current and known locations of amphibians did not differ in elevation, size, lake type, presence of shallow water or emergent vegetation on the north shore, or presence of trout. Water chemistry at amphibian breeding sites was variable, but pH decreased significantly with increasing elevation. Causes of declines of B. boreas and R. pipiens are not known. Populations of B. boreas in the North Fork of the Big Thompson River are critically important to the conservation of this species in the Rocky Mountains.

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