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At least 1,423 records · Page 79Linked to original sources
USGS1971

Hydrologic reconnaissance of the Park Valley area, Box Elder County, Utah

This report is the eighth in a series prepared by the U. S. Geological Survey in cooperation with the Utah Department of Natural Resources, Division of Water Rights, that describes the water resources of the western basins of Utah. (See fig. 1.) Its purpose is to present available hydrologic data on the Park Valley area, to provide an evaluation of the potential water-resource development of the area, and to identify needed studies that would improve understanding of the area's water supply.

Utah↗
USGS2003

Water resources management plan, Richmond National Battlefield Park, Virginia

Richmond National Battlefield Park (Richmond NBP) consists of 1,366 acres in 11 geographically separate units that are located primarily east, northeast, and southeast of the city of Richmond, Virginia. This Water Resources Management Plan addresses nine of the units: Beaver Dam Creek, Chickahominy Bluff, Cold Harbor (including the Garthright House), Drewry’s Bluff, Fort Harrison, Gaines’ Mill, and Glendale and Malvern Hill. The units are in the Atlantic Coastal Plain Physiographic Province between the James and York rivers. The small streams that drain each of the units are tributaries of either the Chickahominy River or James River and ultimately contribute to the Chesapeake Bay.

Virginia↗
USGS2017

Pacific Island landbird monitoring report, Hawaiʻi Volcanoes National Park, 2015-2016: Tract groups 1 and 2

Hawaiʻi Volcanoes National Park (HAVO) was surveyed for landbirds and landbird habitat from February through April 2015 and February through April 2016. This information provides the second datum in the time-series of Pacific Island Network (PACN) monitoring for long-term trends in landbird distribution, density, and abundance. Initial PACN surveys were conducted in 2010 and are repeated every five years. The entire survey area was comprised of eight tracts in forest, woodland, and shrub habitat, totaling 26,364 ha. Each tract was surveyed using point-transect distance sampling to calculate estimates of bird abundance and density. In addition to the permanent PACN survey transects, randomly generated point-transects were also surveyed, allowing for a split panel sampling design. A total of 14,061 bird detections of twenty-eight species were recorded during point counts; 8 species were native to Hawaiʻi and 20 species were non-native. ʻApapane (Himatione sanguinea) and Hawaiʻi ‘Amakihi (Chlorodrepanis virens virens) were the most abundant and widely distributed native species detected. ‘Ōma’o (Myadestes obscurus), ‘I‘iwi (Drepanis coccinea), and Hawaiʻi Elepaio (Chasiempis sandwichensis) occurred at fewer than 30% of the 757 stations surveyed, and were absent from some tracts. Three species of native birds detected during surveys were endangered—ʻIo (Buteo solitarius), Hawaiʻi Creeper (Loxops mana), and Hawaiʻi ʻAkepa (Loxops coccineus). Two additional endangered species were detected incidentally on transects—Nēnē (Branta sandwicensis) and ʻAkiapolaʻau (Hemignathus wilsoni). Non-native Japanese White-eye (Zosterops japonicus), Northern Cardinal (Cardinalis cardinalis), Japanese Bush Warbler (Horomis diphone), and Yellow-fronted Canary (Crithagra mozambica) were detected throughout most tracts and had the highest relative abundances among non-natives. The remaining species detected occurred at less than 10% of stations surveyed. Sufficient detections to allow density estimation were made for 11 species (5 native and 6 non-native). Changes in species-specific densities by tract were assessed between the initial and current surveys using two-sample z-tests in an equivalence testing framework to determine long-term trends. Differences between densities were highly variable for native species; including increasing, decreasing and stable trends. There were notable increases of ‘I‘iwi and ‘Ōma’o densities in some tracts. However there were also declines of ‘Ōma’o in three tracts, including leeward Northwest Kahuku where birds were detected in 2010 for the first time in over 30 years, but not during this recent survey. ‘I‘iwi densities increased in the high elevation Pāpā tract; however, they declined in the Mauna Loa Strip tract where the species may be vulnerable to avian malaria. Trend results for Hawaiʻi ʻAkepa were inconclusive, but the species occurred at more survey stations than in 2010, and we estimate a density of 0.31 ±0.34 birds/ha in the 10,989 ha Kahuku tract. Hawaiʻi Creeper had in an increasing trend in the Kahuku tract with a density of 0.16 ± 0.07 birds/ha and an inconclusive trend in Honomalino, where there was only one detection in 2016. There was a large expansion in the distribution and abundance of the non-native Yellow-fronted Canary and Japanese Bush Warbler. The Lavender Waxbill (Estrilda caerulescens) was detected in HAVO for the first time. Trend results were variable for other non-native species, but generally maintained stable densities when compared to previous landbird surveys. Several habitat variables were sampled at monitoring stations in each tract. Canopy and understory species were predominantly native, especially in tracts where ungulates have been excluded.

Hawai'i↗
USGS1999

Stream restoration at Denali National Park and Preserve

Placer mining for gold has severely disturbed many riparian ecosystems in northern regions. We are conducting a long-term project to test methods to promote restoration of a placer-mined watershed in Denali National Park and Preserve. The project included hydrological restoration of the unstable and excessively confined stream with heavy equipment. We stabilized the floodplain with bioengineering techniques, including alder and willow brush bars anchored laterally to the channel and willow cuttings along the channel. A moderate flood near the end of construction showed that the brush bars provided substantial protection, but some bank erosion and changes in slope and sinuosity occurred. Subsequent refinements included greater sinuosity and channel depth, pool/riffie construction with stone weirs, and buried alder and willow brush projecting from the bank. The reconstructed stream and floodplain have remained stable for five years, but have not been re-tested by a another large flood. The willow/alder riparian plant community is naturally revegetating on the new floodplains, but vigorous willows which sprouted from branches in brush bars and banks still provide the erosion protection.

Alaska↗
USGS1995

Census methodologies of Black-legged Kittiwakes in Glacier Bay National Park

Black-legged Kittiwakes ( Rissa tridactyla ) have recently experienced widespread population declines and frequent colony failures throughout the North Pacific. At Glacier Bay National Park, the Margerie Glacier colony was censused visually in 1991 through 1993. In 1993 a new photographic census technique was also tested to assess its feasibility, accuracy, and ease of use, Three years of monitoring data indicate that kittiwake population size declined by about 10% over the three-year period, and that there were near-total colony reproductive failures in 1991 and 1992. Compared to visual colony counts made from a skiff, counting adult kittiwakes from projected 35-mm slides proved to be both more efficient and equally accurate.

Alaska↗
USGS1995

Prey preference of Pacific halibut ( Hippoglossus stenolepis ) in Glacier Bay National Park

Stomach contents were collected from sport-caught halibut in Glacier Bay National Park. Stomach samples containing a combination of fish and invertebrate species were observed less frequently than expected. Small, subtidal, noncommercial crab and cod-like fish (Gadidae) appear to be the most important prey items. In thc dict of Pacific halibut. Preliminary findings suggested that dict changes dramatically with age. The frequency of occurrence of crustaceans and small forage fishes declines with an increase in age while the frequency of occurrence of cod-like fish (Gadidae) and sculpins (Cottidae) increases with an increase in age. In addition, there were few halibut that contained prey items from different taxa whereas multiple items from a single taxa or prey group were common.

Alaska↗
USGS1995

Winter wolf predation in a multiple ungulate prey system, Gates of the Arctic National Park, Alaska

We investigated patterns of winter wolf predation, including prey selection, prey switching, kill rates, carcass utilization, and consumption rates for four wolf packs during three different study periods (March 1989, March 1990, and November 1990) in Gates of the Arctic National Park and Preserve, Alaska. Wolves killed predominantly caribou (165 caribou, seven moose, and five Dall sheep) even when moose and sheep were more abundant. Prey selection varied between study periods. More moose were killed in march 1989, a particularly deep snow year, and more sheep were killed in November 1990 than during other periods. Overall kill rates ranged from 0-8 days/ungulate killed ( x̅ = 2.0, SD = 1.6) and did not vary between study periods. Pack size and species killed explained significant variation in the length of time intervals between kills. Although caribou density varied nearly 40-fold between pack territories, it had little influence on predation characteristics except at low densities, when kill rates may have declined. Caribou distribution had marked effects on wolf predation rate.

Alaska↗
USGS2017

Forecasting stream habitat and Brook Trout responses to climate change in Catoctin Mountain Park

Anticipating and mitigating the effects of climate change is a fundamental challenge for natural resource conservation. In this report, we respond to research needs identified by Catoctin Mountain Park (CATO) for native Brook Trout (Salvelinus fontinalis) conservation and management as part of the US Geological Survey (USGS) Natural Resources Preservation Program in FY15-16. We addressed three overarching research questions: (1) How will anticipated changes in air temperature affect stream habitats? (2) How will changes to stream habitat affect the distribution of Brook Trout? (3) Which stream segments are most and least vulnerable to the effects of climate change? First, we surveyed Brook Trout abundance and fish community composition using electrofishing techniques within three watersheds: Owens Creek, upper Big Hunting Creek, and Blue Blazes Creek (a tributary to Big Hunting Creek). Second, we deployed a network of stream temperature gages to assess spatial variation in stream temperature and groundwater (GW) influence. Third, we used modeling techniques to forecast future stream temperatures that account for GW influences and air temperature scenarios. Fish sampling detected 13 species and 15,345 individual fish, the majority of which were Blacknose Dace (60%), Blue Ridge Sculpin (26%), and Brook Trout (6%). Brook Trout were not observed in Blue Blazes Creek and exhibited higher densities in Owens Creek than upper Big Hunting Creek (average densities = 19 fish/100 m and 4 fish/100 m, respectively). In contrast, Brown Trout were present in Blue Blazes Creek and exhibited greater density in Blue Blazes Creek than either Owens Creek or upper Big Hunting Creek (average densities = 3.0 fish/100 m, 0.3 fish/100 m, and 1.7 fish/100 m, respectively). Brown Trout occurred in sympatry with Brook Trout in Owens Creek and upper Big Hunting Creek, but appeared to have replaced Brook Trout in Blue Blazes Creek. Our fish surveys also revealed important locations for Brook Trout reproduction and young-of-year (YOY) dispersal within the Owens Creek watershed. Our study also revealed surprising differences in the distribution of Blue Ridge Sculpin among CATO streams. This species was abundant in Owens Creek (average density = 83 fish/100 m) but was less common in Blue Blazes Creek (average density = 12 fish/100 m) and was not detected in upper Big Hunting Creek. Histological examination of several specimens from Blue Blazes Creek by V. Blazer at the USGS Leetown Science Center revealed the presence of a novel parasite (Dermosystidium sp.) which has been linked to fish population declines elsewhere (Blazer et al. 2016). The parasite was not detected in Blue Ridge Sculpin samples from Owens Creek, and all trout appeared to be uninfected. Our survey results suggest that Blue Ridge Sculpin have been extirpated from upper Big Hunting Creek and have not recolonized from downstream source populations due to the fish passage barrier of Cunningham Falls. We recommend additional research to (1) evaluate the feasibility of reintroducing Blue Ridge Sculpin into upper Big Hunting Creek and (2) continue monitoring the distribution and potential spread of Dermocystidium in downstream waters. Stream temperatures ranged from 9.6 – 27.6 ºC during baseflow conditions in 2015 and 2016. Sites within upper Big Hunting Creek were consistently warmer than in Owens Creek or Blue Blazes Creek, suggesting an effect of headwater ponds outside CATO on upper Big Hunting Creek temperatures. For instance, in 2016 the maximum observed temperature in upper Big Hunting Creek was 27.6 ºC whereas Owens Creek reached a maximum of 23.7 ºC that year. Stream temperature data also revealed that 2016 was warmer than 2015 throughout the study area but did not exceed thermal tolerance limits for Brook Trout in either year. We estimated the influence of GW on stream temperatures using a statistical modeling approach based on the relationship between daily mean air temperature and stream temperature over time. Results indicated that effects of GW were generally stronger in the Owens Creek watershed than in Blue Blazes or upper Big Hunting Creek. However, we detected substantial spatial variation in GW influence among Owens Creek sites, with stream temperatures at some locations showing relatively little GW influence and others showing very strong influences (and correspondingly small influence of daily mean air temperatures). Although incoming lateral seeps were detected in upper Big Hunting Creek (D. Ferrier, Hood College, personal communication), the strongest effects of GW in the study area were due to GW upwelling within portions of the Owens Creek watershed (i.e., Tributary C in Figure 4) where we also observed high numbers of Brook Trout juveniles. Our results therefore identified potential high-priority areas for Brook Trout conservation in CATO. Finally, we modeled future stream temperatures based on scenarios characterizing GW sensitivity to air temperature and future air temperature increases. Stream temperature forecasts revealed important differences in habitat suitability for Brook Trout within and among watersheds. Big Hunting Creek sites were generally more sensitive to air temperature increases than sites in Owens Creek or Blue Blazes Creek. For instance, an increase in mean annual air temperature of 1.5 ºC (lowest level evaluated) exceeded thermal thresholds for Brook Trout in the majority of sites within that watershed, regardless of GW influence levels. In contrast, an air temperature increase of 1.5 ºC did not exceed thermal thresholds for Brook Trout in Owens Creek. However, modeled air temperature increases of 5 ºC resulted in a loss of Brook Trout thermal suitability throughout the study area. Model results revealed spatially patchy responses to air temperature increases that could provide an early-warning system for trout monitoring designs in CATO.

Maryland↗
USGS2006

Changes in the C storage in Las Tablas de Daimiel National Park (PNTD) in the last 1000 years [Cambios en el almacenamiento de C en el Parque Nacional de Las Tablas de Daimiel (PNTD) en los últimos 1000 años]

Las Tablas de Daimiel National Park has suffered too many modifications throughout its history, natural as well as anthropic, which have affected the carbon storage in different ways. The study of those variations has been carried out by the analysis of sedimentary record and historical data. The sedimentary record has been studied from the core Ciguela 4. It was sampled with a systematic high resolution method (0.7 cm thickness average) to analyze geochemistry and pollen. The analysis of all data shows that the natural changes (linked with the climate) have more variation ranges than the anthropic ones, are directly related with the climate and not with the concentration of the atmospheric CO2, showing a natural cyclicity with a fast mitigation (decades) of the variations. In the other hand the anthropogenic impacts depend on the proximity and intensity of the impact. The usage changes produced during the second half of the 19th century were an indirect impact with medium intensity. The environment had the capacity to recover the values of a normal storage in less than 50 years. Nevertheless the dissication and overexploitation of the groundwater (second half of 20th century) were direct and high intensity impacts. These impacts caused a fast loss of the water table and the salinization of the environment. Due to that the ecosystem lost capacity to store C. recovery of the normal values by a natural way is difficult now.

Las Tablas de Daimiel National Park↗
USGS2015

Acadia National Park climate change scenario planning workshop summary

This report summarizes outcomes from a two-day scenario planning workshop for Acadia National Park, Maine. The primary objective of the workshop was to help Acadia senior leadership make management and planning decisions based on up-to-date climate science and assessments of future uncertainty. The workshop was also designed as a training program, helping build participants' capabilities to develop and use scenarios. The details of the workshop are given in later sections. The climate scenarios presented here are based on published global climate model output. The scenario implications for resources and management decisions are based on expert knowledge distilled through scientist-manager interaction during workgroup break-out sessions at the workshop. Thus, the descriptions below are from these small-group discussions in a workshop setting and should not be taken as vetted research statements of responses to the climate scenarios, but rather as insights and examinations of possible futures. Here we provide the main conclusions from the scenario planning workshop.

Maine↗
USGS2019

Assessing spatial and temporal patterns in sagebrush steppe vegetation communities 2012-2018: Grand Teton National Park

Visual cover class data were collected on over 80 species across 30 permanent sampling frames in sagebrush steppe vegetation communities in Grand Teton National Park from 2012 to 2018. In this report, temporal and spatial patterns in species composition were assessed and used to inform potential sampling strategies for future monitoring. Specifically, the viability of a reduction in sampling effort was evaluated based on the similarity in species composition within each frame over time and among frames within each year. Using distance-based ordination techniques, we found little to no evidence of differences in species composition within each frame over time. Furthermore, there was little evidence of heterogeneity in species composition among frames within each year, though there was some evidence of differences in composition between the two principle sagebrush community types (sagebrush dry shrubland and sagebrush-bitterbrush) aggregated across frames. Based on these results, we propose that a reduction in sampling effort is viable and suggest a new monitoring schedule.

Wyoming↗
USGS2021

Demographic responses to density-dependence by two populations of the Florida Tree Snail, Liguus fasciatus (Gastropoda: Orthalicidae), in Everglades National Park

D uring May-October 1996, we captured and individually marked and released Florida Tree Snails, Liguus fasciatus, from two sites, a subclimax hammock and a large isolated wild tamarind tree, in the Long Pine Key region of Everglades National Park. Populations shared the same two dominant morphs, castaneozonatus and. cingulatus, both of which are strong colonizers. Monthly survivorship between the two sites were comparable, although annual survivorship was lower on the isolated tree. Intersite differences in growth rates were equivocal. The populations differed with respect to number of morphs, population size, and population structure. The hammock site was a subclimax hammock with a large and stable bell-shaped population structure comprising nine morphs. In contrast, the population structure of the single tree was highly skewed, with many young individuals produced, intermediate ages absent, and few large adults of larger asymptotic size present. Number of snails/m was higher on the isolated tree. Demographic studies of the Florida Tree Snail are uncommon. Our findings corroborate certain aspects of the ecology of this species and clarify two different demographic responses, one of stability, and one of apparent resource limitation whose demography represents opportunities for colonization.

Florida↗
USGS1975

Mobilization of iron in water in the Magothy aquifer during long-term recharge with tertiary-treated sewage, Bay Park, New York

Tertiary-treated sewage (reclaimed water) has been recharged by well into the Magothy aquifer at Bay Park, N. Y., intermittently since 1968. The longest of 13 recharge tests, the subject of this report, lasted 84.5 days. This was sufficient time for the reclaimed water to reach an observation well 200 ft (61 m) from the recharge well. Although the iron concentrations of the reclaimed water and the native water were less than 0.4 mg/l, the iron concentrations of samples from observation wells 20, 100, and 200 ft (6, 30, and 61 m) from the recharge well at times approached 3 mg/l. Source of the ii'on is pyrite that is native to the aquifer.

New York↗
USGS1978

Iron in water near wastewater lagoons in Yellowstone National Park, Wyoming

High dissolved-iron concentrations have been noted in water in wells used to monitor effluent that percolates from wastewater disposal lagoons near Old Faithful in Yellowstone National Park. The concentration of dissolved iron in water in a well increased from 80 μ g/L (micrograms per liter) before a nearby lagoon was .used for disposal of effluent to 17000 μ g/L after the lagoon was used. The effluent contained 180 μ g/L of dissolved iron, and nearby Iron Spring Creek contained 30 μ g/L or less of dissolved iron above and below the lagoons. Organic carbon, nitrogen, and sulfur in the effluent as methane, ammonia, and hydrogen sulfide are oxidized to carbon dioxide, nitrate, and sulfate, respectively, in the unsaturated zone and possibly in the saturated zone as ground water moves through sand and gravel toward Iron Spring Creek. This oxidation results in simultaneous reduction of iron in the sand and gravel from the insoluble ferric phase to the soluble ferrous phase. As ground water high in dissolved iron discharges at land surface near the stream, oxygen from the atmosphere oxidizes the iron back to the insoluble ferric phase, and ferric hydroxide precipitates. Ferric hydroxide also precipitates in some of the monitoring wells. Iron bacteria and other organisms are associated with the precipitates.

Wyoming↗
USGS2022

Geologic map of the Mount Blue Sky (formerly Mount Evans) quadrangle, Clear Creek and Park Counties, Colorado

The Mount Blue Sky (formerly Mount Evans) 7.5’ quadrangle lies in Park and Clear Creek counties, Colorado, about 60 km west of Denver. The highest elevation in the quadrangle is 14,265 ft (4,348 m) at the top of Mount Blue Sky. The lowest is at about 9,200 ft (2,804 m) on Guanella Pass Road at the southern edge of the quadrangle. Bedrock directly underlies most of the map area, with surficial deposits primarily in the valleys. The geology of the quadrangle was previously mapped at 1:100,000 scale as part of a regional compilation by Kellogg and others (2008). The oldest rocks in the Mount Blue Sky 7.5-minute quadrangle are Paleoproterozoic metasedimentary rocks, and mafic to felsic metaigneous rocks (all units starting with ‘X’ on Plate 1). These rocks were metamorphosed under upper amphibolite facies conditions and intruded by Mesoproterozoic felsic igneous rocks of the ~1442 Ma Mount Blue Sky (YgR, Yt, Ygdm, Ymgm and ~1424 Ma Silver Plume (Yg) batholiths (Spurr and others, 1908; Tweto, 1897; Aleinikoff and others, 1993; du Bray and others, 2018) and, in the southern part of the quadrangle, by rocks that may also be part of the Mount Blue Sky batholith, but may alternatively interpreted as part of the ~1115 Ma to ~1066 Ma Pikes Peak batholith (Unruh and others, 1995; Guitreau and others, 2016). Four generations of folds affected the area. The oldest, F1 folds are isoclinal of various orientations, but primarily northerly-plunging in the southern part of the quadrangle (Mahatma, 2019; Mahatma and others, 2022). In the northern part of the quadrangle (Powell, 2020), open to close F2 chevron folds exist with various orientations. F3 folds in the northern part of the quadrangle are open to close with upright axial planes and plunges to the north and south, and in the southern part of the quadrangle they are open centimeter- to meter- scale northerly-plunging folds, possibly overprinted by another generation of northerly-plunging folds based on orientations of axial planes (F2 and F3 of Mahatma and others, 2022). F4 folds throughout the quadrangle are open to gentle with upright axial planes and shallow plunges to the east and west. The Mount Blue Sky batholith displays a pervasive moderately NW-dipping biotite-hornblende foliation (Fig. 1) in addition to a flow foliation near the margins, indicating NW-directed shortening after ~1442 Ma (Powell, 2020). The relationship between this foliation and the folds is not clear. Various joint sets are present in the area. The most pervasive joint set strikes 355°-020° and is subvertical. It is best developed in the western to southwestern part of the map area, and may be related to late Cenozoic extension associated with the Rio Grande Rift. Joint orientations are generally consistent with the trends of topographical lineaments. Surficial deposits include two series of glacial till deposits (Qtb and Qtp), and outwash (Qgp) deposits. They correlate with the Bull Lake (170-120 ka) and Pinedale (30-12 ka) glacial periods (Dahms, 2004) based on original depositional morphology, geomorphic and topographic position, deposit weathering and pedogenic properties. Possible older glacial deposits (Qti) have been observed along topographically higher surfaces.

Colorado↗
USGS2023

Mapping a glide avalanche with terrestrial lidar in Glacier National Park, USA

Thorough documentation of large avalanche events is important for forecasting efforts, infrastructure planning, and investigating the processes involved in avalanche formation and release. However, due in part to the isolated and dangerous nature of avalanche terrain, collecting in-situ, spatially continuous, and quantitative information surrounding avalanches remains difficult. Advances in remote sensing continue to address this knowledge gap. For example, terrestrial laser scanners (TLSs) can produce snow depth measurements at fine spatial resolutions over large areas. Repeat data acquisitions between precipitation events also allow for depth quantification atop an interface, as well as precise estimations of release volume and runout area after avalanche failure. Here, we explore the benefits of TLS-derived documentation from a large avalanche event by examining the development and release of a glide avalanche that occurred in Glacier National Park, Montana, USA, during the spring of 2022. Three sets of lidar point cloud data were acquired in the Haystack Creek drainage, focused on a well-known glide avalanche site. Lidar scans were collected after glide cracks emerged but prior to glide failure, and shortly (~ 1.5 days) after avalanche occurrence, in addition to a snow-free scan later in the year. With this temporal dataset, we were able to account for and visualize the spatial variability of snow depth across the avalanche start zone, such that we could precisely calculate the release volume (18674 m3) and average start zone depth (3.3 m) of the avalanche. Furthermore, TLS data were used to map the extent of the runout area and entrainment zone.

Montana↗
USGS2016

Katmai National Park and Preserve and Alagnak Wild River: Geologic resources inventory report

The Geologic Resources Inventory (GRI) is one of 12 inventories funded by the National Park Service (NPS) Inventory and Monitoring Program. The Geologic Resources Division of the NPS Natural Resource Stewardship and Science Directorate administers the GRI. This GRI report was written for resource managers to support science-informed decision making. It may also be useful for interpretation. The report was prepared using available geologic information. Chapters of the report discuss distinctive geologic features and processes, describe the geologic history leading to the present- day landscape, highlight geologic issues facing resource managers, and provide information about the associated GRI geologic map data. A poster (Plate 1, in pocket) illustrates these data.

Alaska↗
USGS2002

Sustainability of vegetation communities grazed by elk in Rocky Mountain National Park

Current management of the worlds' grazing lands in either based on changes in plant species composition or on other management evaluation programs that emphasize changes in net aboveground production. Management is based solely on changes in aboveground production has been criticized as too limited in view, because it ignores root production, nitrogen pools, nutrient processes, and the long-term sustainability of the ecosystem. The purpose of this study was to compare the effects of elk ( Cervus elaphus ) grazing on aboveground production, internal nitrogen (N) fluxes, N pools and inputs, and elk nutrient transfers across the landscape in different vegetation types in Rocky Mountain National Park (RMNP), Colorado. Nitrogen processes and possibly N pools were significantly reduced in the willow community, but not in the upland grass/shrub community. Nitrogen mineralization rates were lower in grazed versus ungrazed short willow sites (P = 0.07; n = 4 sites), as were nitrate (NO3) pools (P = 0.10), but not in tall willow sites (P > 1.10 n = 4 sites) after 4 years. There was about half the annual N inputs to the soil surface in grazed willow sites (5.79g N/m 2 /yr = annual herbaceous biomass a?? offtake + litterfall + elk urine and feces) compared to ungrazed sites (9.66 g N/m 2 /yr = annual herbaceous biomass + litterfall), suggesting elk herbivory and movement led to a net loss of N in the willow vegetation type. Elk substantially reduced the annual growth of willows (Salix spp.) by 98% after 35 years and 66% after 4 years of treatment. Thus, height and canopy and N yield of willows were reduced as well as willow litter biomass (65 g/m2/yr in ungrazed versus 33 g/m2/yr in grazed), and N yield of willows was 64% less in grazed plots. Elk grazing had no significant effect on other soil N pools (NH4) or litter decomposition rates in either of the two willow types, nor on any nitrogen process rates or pools in the upland grass/shrub type (P > 0.10). Nitrogen concentrations in plant tissue were not influenced for the most part by elk grazing (increased N concentration found in only 4 of 13 species). Elk apparently also transported N away from aspen at an even higher rate (N inputs were 1.65 g N/m2/yr in grazed sites vs. 3.79 g N/m 2 /yr ungrazed). CENTURY modeling supported these observations. This soil N model predicted almost no change (0.5$ - 2% less) in N or carbon (C) pools in 50 years in the upland grass/shrub vegetation type, but greater losses in the willow type. If elk population levels were increased to carrying capacity in the ecosystem (about 25% more consumption) projected losses after 50 years were greater, but still <4% for soil C and 1% for spoil N in the upland type, and 6% for soil C and 2% for soil N in the willow type. Total shrub C was projected to decline 10% in 50 years in the willow type at current elk densities. We recommend conservative management of elk numbers and grazing until additional years of measures are gathered on the lower mineralization rates in the short willow type and until the projected declines in N pools can be verified.

Report↗