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Research about Nevada

Source-linked reports with geographic coverage including Nevada.

At least 271 records · Page 15Linked to original sources
USGS2013

Information to support to monitoring and habitat restoration on Ash Meadows National Wildlife Refuge

The Ash Meadows National Wildlife Refuge staff focuses on improving habitat for the highest incidence of endemic species for an area of its size in the continental United States. Attempts are being made to restore habitat to some semblance of its pre-anthropogenic undisturbed condition, and to provide habitat conditions to which native plant and animal species have evolved. Unfortunately, restoring the Ash Meadows’ Oases to its pre-anthropogenic undisturbed condition is almost impossible. First, there are constraints on water manipulation because there are private holdings within the refuge boundary; second, there has been at least one species extinction—the Ash Meadows pool fish ( Empetrichthys merriami ). It is also quite possible that thermal endemic invertebrate species were lost before ever being described. Perhaps the primary obstacle to restoring Ash Meadows to its pre-anthropogenic undisturbed conditions is the presence of invasive species. However, invasive species, such as red swamp crayfish ( Procambarus clarki ) and western mosquitofish ( Gambusia affinis ), are a primary driving force in restoring Ash Meadows’ spring systems, because under certain habitat conditions they can all but replace native species. Returning Ash Meadows’ physical landscape to some semblance of its pre-anthropogenic undisturbed condition through natural processes may take decades. Meanwhile, the natural dissolution of concrete and earthen irrigation channels threatens to allow cattail marshes to flourish instead of spring-brooks immediately downstream of spring discharge. This successional stage favors non-native crayfish and mosquitofish over the native Amargosa pupfish ( Cyprinodon nevadensis ). Thus, restoration is needed to control non-natives and to promote native species, and without such intervention the probability of native fish reduction or loss, is anticipated. The four studies in this report are intended to provide information for restoring native fish habitat and for monitoring native fish populations in relation to restoration efforts on the Ash Meadows National Wildlife Refuge. There are no precise records on conditions of each of the spring systems prior to anthropogenic alteration; however, fostering conditions that favor native over non-natives will be key to habitat restoration. Information regarding native species carbon source is needed to create habitat that favors native species, thus habitat restoration fostering food stuff consumed by native species should be considered in restoration efforts. In compiling data for the first part of this report, we tracked carbon source for native and non-native species at four stations along the Jackrabbit Spring system. Thus, we were able to contrast carbon source in warm- and cool-water habitats. Habitat in Jackrabbit Spring was improved for native fishes in 2007. The second paper in this report focuses on native fish populations in Jackrabbit Spring system pre- and post-restoration. Much of the Ash Meadows Oases is marsh habitat where non-native red swamp crayfish and western mosquitofish are often abundant, to the detriment of non-natives. Because marsh habitat is broadly represented in the Ash Meadows landscape, establishing marsh habitat most conducive to the native fishes is important to the restoration effort, and the third paper addresses marsh habitat type with the relative abundance of fishes and crayfish. There are previous years of monitoring Ash Meadows’ native fish populations, but not all monitoring occurred at the same time of year. Desert-fish populations sometimes undergo seasonal fluctuation, so it might not be valid to compare population trends using difference seasons. For report four, we tracked a closed population of Amargosa pupfish ( Cyprinodon nevadensis ) year round to track seasonal trends. Knowledge of seasonal trends is important in tracking changes of populations pre- and post-restoration.

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USGS2013

Population estimates for the Toiyabe population of the Columbia spotted frog ( Rana luteiventris ), 2004–10

The Toiyabe population of Columbia spotted frogs ( Rana luteiventris , hereafter "Toiyabe frogs") is a geographically isolated population located in central Nevada (fig. 1). The Toiyabe population is part of the Great Basin Distinct Population Segment of Columbia spotted frogs, and is a candidate for listing under the Endangered Species Act (U.S. Fish and Wildlife Service, 2011). The cluster of breeding sites in central Nevada represents the southernmost extremity of the Columbia spotted frogs' known range (Funk and others, 2008). Toiyabe frogs are known to occur in seven drainages in Nye County, Nevada: Reese River, Cow Canyon Creek, Ledbetter Canyon Creek, Cloverdale Creek, Stewart Creek, Illinois Creek, and Indian Valley Creek. Most of the Toiyabe frog population resides in the Reese River, Indian Valley Creek, and Cloverdale Creek drainages (fig. 1; Nevada Department of Wildlife, 2003). Approximately 90 percent of the Toiyabe frogs' habitat is on public land. Most of the public land habitat (95 percent) is managed by the U.S. Forest Service (USFS), while the Bureau of Land Management (BLM) manages the remainder. Additional Toiyabe frog habitat is under Yomba Shoshone Tribal management and in private ownership (Nevada Department of Wildlife, 2003). The BLM, USFS, Nevada Department of Wildlife (NDOW), Nevada Natural Heritage Program (NNHP), Nye County, and U.S Fish and Wildlife Service (USFWS) have monitored the Toiyabe population since 2004 using mark and recapture surveys (Nevada Department of Wildlife, 2004). The USFWS contracted with the U.S. Geological Survey (USGS) to produce population estimates using these data.

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USGS2013

Extreme ground motions and Yucca Mountain

Yucca Mountain is the designated site of the underground repository for the United States' high-level radioactive waste (HLW), consisting of commercial and military spent nuclear fuel, HLW derived from reprocessing of uranium and plutonium, surplus plutonium, and other nuclear-weapons materials. Yucca Mountain straddles the western boundary of the Nevada Test Site, where the United States has tested nuclear devices since the 1950s, and is situated in an arid, remote, and thinly populated region of Nevada, ~100 miles northwest of Las Vegas. Yucca Mountain was originally considered as a potential underground repository of HLW because of its thick units of unsaturated rocks, with the repository horizon being not only ~300 m above the water table but also ~300 m below the Yucca Mountain crest. The fundamental rationale for a geologic (underground) repository for HLW is to securely isolate these materials from the environment and its inhabitants to the greatest extent possible and for very long periods of time. Given the present climate conditions and what is known about the current hydrologic system and conditions around and in the mountain itself, one would anticipate that the rates of infiltration, corrosion, and transport would be very low—except for the possibility that repository integrity might be compromised by low-probability disruptive events, which include earthquakes, strong ground motion, and (or) a repository-piercing volcanic intrusion/eruption. Extreme ground motions (ExGM), as we use the phrase in this report, refer to the extremely large amplitudes of earthquake ground motion that arise at extremely low probabilities of exceedance (hazard). They first came to our attention when the 1998 probabilistic seismic hazard analysis for Yucca Mountain was extended to a hazard level of 10 -8 /yr (a 10-4/yr probability for a 10 4 -year repository “lifetime”). The primary purpose of this report is to summarize the principal results of the ExGM research program as they have developed over the past 5 years; what follows will be focused on Yucca Mountain, but not restricted to it.

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Habitat quality and recruitment success of cui-ui in the Truckee River downstream of Marble Bluff Dam, Pyramid Lake, Nevada

We compared cui-ui (Chasmistes cujus) recruitment from two reaches of the Truckee River with histories of severe erosional downcutting caused by a decline in Pyramid Lake surface elevation. In 1975, Marble Bluff Dam (MBD) was constructed 5 kilometers upstream of the extant mouth of the Truckee River to stabilize the upstream reach of the river; the downstream reach of the river remained unstable and consequently unsuitable for cui-ui recruitment. By the early 2000s, there was a decrease in the Truckee River’s slope from MBD to Pyramid Lake after a series of wet years in the 1990s. This was followed by changes in river morphology and erosion abatement. These changes led to the question as to cui-ui recruitment potential in the Truckee River downstream of MBD. In 2012, more than 7,000 cui-ui spawners were passed upstream of MBD, although an indeterminate number of cui-ui spawned downstream of MBD. In this study, we compared cui-ui recruitment upstream and downstream of MBD during a Truckee River low-flow year (2012). Cui-ui larvae emigration to Pyramid Lake began earlier and ended later downstream of MBD. A greater number of cui-ui larvae was produced downstream of MBD than upstream. This also was true for native Tahoe sucker (Catostomus tahoensis) and Lahontan redside (Richardsonius egregius). The improved Truckee River stability downstream of MBD and concomitant cui-ui recruitment success is attributed to a rise in Pyramid Lake's surface elevation. A decline in lake elevation may lead to a shift in stream morphology and substrate composition to the detriment of cui-ui reproductive success as well as the reproductive success of other native fishes.

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Stratigraphy of lower to middle Paleozoic rocks of northern Nevada and the Antler orogeny

Commonly accepted concepts concerning the lower Paleozoic stratigraphy of northern Nevada are based on the assumption that the deep-water aspects of Ordovician to Devonian siliceous strata are due to their origin in a distant oceanic environment, and their presence where we find them is due to tectonic emplacement by the Roberts Mountains thrust. The concept adopted here is based on the assumption that their deep-water aspects are the result of sea-level rise in the Cambrian, and all of the Paleozoic strata in northern Nevada are indigenous to that area. The lower part of the Cambrian consists mainly of shallow-water cross-bedded sands derived from the craton. The upper part of the Cambrian, and part of the Ordovician, consists mainly of deep-water carbonate clastics carried by turbidity currents from the carbonate shelf in eastern Nevada, newly constructed as a result of sea-level rise. Ordovician to mid-Devonian strata are relatively deep-water siliceous deposits, which are the western facies assemblage. The basal contact of this assemblage on autochthonous Cambrian rocks is exposed in three mountain ranges and is clearly depositional in all three. The western facies assemblage can be divided into distinct stratigraphic units of regional extent. Many stratigraphic details can be explained simply by known changes in sea level. Upper Devonian to Mississippian strata are locally and westerly derived orogenic clastic beds deposited disconformably on the western facies assemblage. This disconformity, clearly exposed in 10 mountain ranges, indicates regional uplift and erosion of the western facies assemblage and absence of local deformation. The disconformity represents the Antler orogeny.

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The development and application of a decision support system for land management in the Lake Tahoe Basin—The Land Use Simulation Model

This report describes and applies the Land Use Simulation Model (LUSM), the final modeling product for the long-term decision support project funded by the Southern Nevada Public Land Management Act and developed by the U.S. Geological Survey’s Western Geographic Science Center for the Lake Tahoe Basin. Within the context of the natural-resource management and anthropogenic issues of the basin and in an effort to advance land-use and land-cover change science, this report addresses the problem of developing the LUSM as a decision support system. It includes consideration of land-use modeling theory, fire modeling and disturbance in the wildland-urban interface, historical land-use change and its relation to active land management, hydrologic modeling and the impact of urbanization as related to the Lahontan Regional Water Quality Control Board’s recently developed Total Maximum Daily Load report for the basin, and biodiversity in urbanizing areas. The LUSM strives to inform land-management decisions in a complex regulatory environment by simulating parcel-based, land-use transitions with a stochastic, spatially constrained, agent-based model. The tool is intended to be useful for multiple purposes, including the multiagency Pathway 2007 regional planning effort, the Tahoe Regional Planning Agency (TRPA) Regional Plan Update, and complementary research endeavors and natural-resource-management efforts. The LUSM is an Internet-based, scenario-generation decision support tool for allocating retired and developed parcels over the next 20 years. Because USGS staff worked closely with TRPA staff and their “Code of Ordinances” and analyzed datasets of historical management and land-use practices, this report accomplishes the task of providing reasonable default values for a baseline scenario that can be used in the LUSM. One result from the baseline scenario for the model suggests that all vacant parcels could be allocated within 12 years. Results also include: assessment of model functionality, brief descriptions of the 7 basic output tables, assessment of the rate of change in land-use allocation pools over time, locations and amounts of the spatially explicit probabilities of land-use transitions by real estate commodity, and analysis of the state change from today’s existing land cover to potential land uses in the future. Assumptions and limitations of the model are presented. This report concludes with suggested next steps to support the continued utility of the LUSM and additional research avenues.

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Iron mineralogy and bioaccessibility of dust generated from soils as determined by reflectance spectroscopy and magnetic and chemical properties--Nellis Dunes recreational area, Nevada

Atmospheric mineral dust exerts many important effects on the Earth system, such as atmospheric temperatures, marine productivity, and melting of snow and ice. Mineral dust also can have detrimental effects on human health through respiration of very small particles and the leaching of metals in various organs. These effects can be better understood through characterization of the physical and chemical properties of dust, including certain iron oxide minerals, for their extraordinary radiative properties and possible effects on lung inflammation. Studies of dust from the Nellis Dunes recreation area near Las Vegas, Nevada, focus on characteristics of radiative properties (capacity of dust to absorb solar radiation), iron oxide mineral type and size, chemistry, and bioaccessibility of metals in fluids that simulate human gastric, lung, and phagolysosomal fluids. In samples of dust from the Nellis Dunes recreation area with median grain sizes of 2.4, 3.1, and 4.3 micrometers, the ferric oxide minerals goethite and hematite, at least some of it nanosized, were identified. In one sample, in vitro bioaccessibility experiments revealed high bioaccessibility of arsenic in all three biofluids and higher leachate concentration and bioaccessibility for copper, uranium, and vanadium in the simulated lung fluid than in the phagolysosomal fluid. The combination of methods used here to characterize mineral dust at the Nellis Dunes recreation area can be applied to global dust and broad issues of public health.

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Properties of basin-fill deposits, a 1971–2000 water budget, and surface-water-groundwater interactions in the upper Humboldt River basin, northeastern Nevada

This study was done in cooperation with Elko County, Nevada in response to concerns over growing demand for water within the county and increasing external demands that are occurring statewide. The upper Humboldt River basin encompasses 4,360 square miles in northeastern Nevada and includes the headwaters area of the Humboldt River. Nearly all of the mean annual flow of the Humboldt River originates in this area. Basin-fill deposits function as the principal aquifers in the upper Humboldt River basin. Over much of the basin lowlands, the upper 200 feet of basin fill consists of clay, silt, sand, and gravel deposited in a lake of middle to late Pliocene age. Fine-grained lacustrine sediments compose from 30 to more than 70 percent of the deposits. Mean values of transmissivity are less than 1,000 feet squared per day. Total inflow to the upper Humboldt River basin, about 3,330,000 acre-feet per year, is entirely from annual precipitation. Total outflow from the basin, about 3,330,000 acre-feet per year, occurs as evapotranspiration, streamflow, subsurface flow, and pumpage. The uncertainty of these values of inflow and outflow is estimated to be 25 percent. Baseflow of the Humboldt River is minimal upstream of the Elko Hills and in downstream reaches almost all baseflow comes from tributary inflow of the North Fork and South Fork Humboldt Rivers. However, the baseflow of these two tributaries comes from groundwater discharge to their respective channels in canyons incised in volcanic rocks along the North Fork and in carbonate rocks along the South Fork. Water levels in the shallow water-table aquifer along the Humboldt River flood plain fluctuate with changes in stage of the river. During high rising river stage in spring and early summer, streamflow enters the aquifer as bank storage. As stage begins to decline in early to mid-summer groundwater in bank storage begins discharging back into the river channel and this continues through late summer. In years of below average flow some reaches of the river are dry in late summer. Flood plain deposits are more permeable than adjacent and underlying fine-grained sediments of the Pliocene lake and the two aquifers are poorly connected.

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The distribution and modeling of nitrate transport in the Carson Valley alluvial aquifer, Douglas County, Nevada

Residents of Carson Valley in Douglas County, Nevada, rely on groundwater from an alluvial aquifer for domestic use and agricultural irrigation. Since the 1970s, there has been a rapid increase in population in several parts of the valley that rely on domestic wells for drinking water and septic systems for treatment of household waste. As a result, the density of septic systems in the developed areas is greater than one septic system per 3 acres, and the majority of the domestic wells are shallow (screened within 250 feet of the land surface). The distribution of nitrate as nitrogen (referred to herein as nitrate-N) concentrations in groundwater was determined by collecting more than 200 samples from 8 land-use categories: single family residential, multifamily residential, rural (including land use for agriculture), vacant land, commercial, industrial, utilities, and unclassified. Nitrate-N concentrations ranged from below detection (less than 0.05 milligrams per liter) to 18 milligrams per liter. The results of nitrate-N concentrations that were sampled from three wells equalled or exceeded the maximum contaminant level of 10 milligrams per liter set by the U.S. Environmental Protection Agency. Nitrate-N concentrations in sampled wells showed a positive correlation between elevated nitrate-N concentrations and the percentage of single-family land use and septic-system density. Wells sampled in other land-use categories did not have any correlation to nitrate-N concentrations. In areas with greater than 50-percent single-family land use, nitrate-N concentrations were two times greater than in areas with less than 50 percent single-family land use. Nitrate-N concentrations in groundwater near septic systems that had been used more than 20 years were more than two times greater than in areas where septic systems had been used less than 20 years. Lower nitrate-N concentrations in the areas where septic systems were less than 20 years old probably result from temporary storage of nitrogen leaching from septic systems into the unsaturated zone. In areas where septic systems are abundant, nitrate-N concentrations were predicted to 2059 by using numerical models within the Ruhenstroth and Johnson Lane subdivisions in the Carson Valley. Model results indicated that nitrate-N concentrations will continue to increase and could exceed the maximum contaminant level over extended areas inside and outside the subdivisions. Two modeling scenarios were used to simulate future transport as a result of removal of septic systems (source of nitrate-N contamination) and the termination of domestic pumping of groundwater. The models showed the largest decrease in nitrate-N concentrations when septic systems were removed and wells continued to pump. Nitrate-N concentrations probably will continue to increase in areas that are dependent on septic systems for waste disposal either under current land-use conditions in the valley or with continued growth and change in land use in the valley.

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Habitat interaction between two species of chipmunk in the Basin and Range Province of Nevada

Interspecies interactions can affect how species are distributed, put constraints on habitat expansion, and reduce the fundamental niche of the affected species. Using logistic regression, we analyzed and compared 174 Tamias palmeri and 94 Tamias panamintinus within an isolated mountain range of the Basin and Range Province of southern Nevada. Tamias panamintinus was more likely to use pinyon/ponderosa/fir mixed forests than pinyon alone, compared to random sites. In the presence of T palmeri , however, interaction analyses indicated T. panamintinus was less likely to occupy the mixed forests and more likely near large rocks on southern aspects. This specie s-by-habitat interaction data suggest that T. palmeri excludes T panamintinus from areas of potentially suitable habitat. Climate change may adversely affect species of restricted distribution. Habitat isolation and species interactions in this region may thus increase survival risks as climate temperatures rise.

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Distribution and movement of Big Spring spinedace ( Lepidomeda mollispinis pratensis ) in Condor Canyon, Meadow Valley Wash, Nevada

Big Spring spinedace (Lepidomeda mollispinis pratensis) is a cyprinid whose entire population occurs within a section of Meadow Valley Wash, Nevada. Other spinedace species have suffered population and range declines (one species is extinct). Managers, concerned about the vulnerability of Big Spring spinedace, have considered habitat restoration actions or translocation, but they have lacked data on distribution or habitat use. Our study occurred in an 8.2-km section of Meadow Valley Wash, including about 7.2 km in Condor Canyon and 0.8 km upstream of the canyon. Big Spring spinedace were present upstream of the currently listed critical habitat, including in the tributary Kill Wash. We found no Big Spring spinedace in the lower 3.3 km of Condor Canyon. We tagged Big Spring spinedace ≥70 mm fork length (range 70–103 mm) with passive integrated transponder tags during October 2008 (n = 100) and March 2009 (n = 103) to document movement. At least 47 of these individuals moved from their release location (up to 2 km). Thirty-nine individuals moved to Kill Wash or the confluence area with Meadow Valley Wash. Ninety-three percent of movement occurred in spring 2009. Fish moved both upstream and downstream. We found no movement downstream over a small waterfall at river km 7.9 and recorded only one fish that moved downstream over Delmue Falls (a 12-m drop) at river km 6.1. At the time of tagging, there was no significant difference in fork length or condition between Big Spring Spinedace that were later detected moving and those not detected moving. We found no significant difference in fork length or condition at time of tagging of Big Spring spinedace ≥70 mm fork length that were detected moving and those not detected moving. Kill Wash and its confluence area appeared important to Big Spring spinedace; connectivity with these areas may be key to species persistence. These areas may provide a habitat template for restoration or translocation. The lower 3.3 km of Meadow Valley Wash in Condor Canyon may be a good candidate section for habitat restoration actions.

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Science-based management of public lands in southern Nevada

Landmark legislation provides guiding principles for land management planning in southern Nevada and the rest of the United States. Such legislation includes, but is not limited to, the Forest Service Organic Administration Act of 1897 (16 U.S>C. 473-478, 479-482 and 551), National Park Service Organic Act of 1916 (U.S.C. Title 16, Secs. 1-4). Wilderness Act 1964 (P.L.88-577), National Environmental Policy Act of 1969 (P.L. 91-190), Endangered Species Act of 1973 (P.L. 91-205), National Forest Management Act of of 1976 (P.L. 94-588), and Federal Land Policy and Management Act of 1976 (P.L. 94-579). The acts establishing congressionally designated areas within southern Nevada, such as Lake Mead National Recreation Area, Spring Mountains National Restoration Area, and Desert National Wildlife Refuge, also contain guidelines for the management of these lands. These documents variously require preservation of natural and cultural resource and wilderness character, protection of species, and prevention of undesirable environmental effects from land management actions. These requirements must be met while allowing for multiple "uses" of certain public lands (e.g. recreation, ranching, resources extraction, renewable energy development, etc.) to the degree that they do no threaten preservation, protection, and prevention goals,. many considerations some into play in the development and implementation for land management plans and actions. The planning process requires a balancing act that sometimes pit one need or priority against another. When priorities can trump other needs can prioritized and receive disproportionate consideration. Overall, the management of public lands is a very complicated and sometime contentious process. Science provides an objective way to help weigh quantifiable information and draw conclusions about the effects of past and potential future land management policies, decisions, and actions. When effectively integrated into adaptive management, science-based information can reduce uncertainties, increase knowledge, and improve decision making. However, the specific science information needed for effective management is often lacking or difficult to access or interpret. Science is typically reported in scientific journals as discrete units describing individual studies with other scientists as the primary audience. Translations of these studies an synthesis or multiple studies into formats that can be readily used in land management planning efforts are often lacking. Identifying and articulating the highest priority science and research needs is one of the primary purposes of the Southern Nevada Agency Partnership (SNAP; http://www.SNAP.gov) Science and Research Team (chapter 1; Turner and others 2009). The SNAP Science and Research Strategy (Strategy) calls for a synthesis report to be written every 5 years summarizing the state of knowledge, information gaps and management implications of scientific information as it relates to the SNAP Strategy goals (Turner and others 2009). This General Technical Report serves as the first SNAP Science and Research Synthesis Report (Synthesis Report) commissioned by the Science and Research Team. The Synthesis Report is mostly based on information form the peer-reviewed scientific literature, and is itself peer reviewed and constitutes a new contribution to the scientific literature. This final chapter addresses Sub-goal 2.3, which is to manage current and future authorized southern Nevada land uses in a manner that balances public need and ecosystem sustainability, and Sub-goal 2.5, which is to promote an effective conservation education and interpretation program to improve the quality of resources and enhance public use and enjoyment of southern Nevada public lands. It summarizes information form the previous chapters on what scientific information is known currently and what remains largely unknown, and it discusses how science can be used to make future management decisions that balances public needs and ecosystem sustainability.

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Ecosystem stressors in southern Nevada

Southern Nevada ecosystems and their associated resources are subject to a number of global and regional/local stressors that are affecting the sustainability of the region. Global stressors include elevated carbon dioxide (CO 2 ) concentrations and associated changes in temperature and precipitation patterns and amount, solar radiation, and nutrient cycles (Smith and others 2009b). Global stressors are ubiquitous in nature and interact both directly and indirectly with regional or local stressors. Regional/local stressors in southern Nevada include: population growth and urbanization and associated increases in nitrogen deposition, energy development, water development, and recreation; increased effects of insects and disease; ongoing effects of livestock, wild horse and burro grazing; new and expanding invasive species; and altered fire regimes. This chapter provides background information on the stressors affecting southern Nevada's ecosystems that is needed to address Goal 1.0 in the SNAP Science Research Strategy, which is to restore, sustain, and enhance southern Nevada's ecosystems (Turner and others 2009). Human population growth and changes in land use strongly affect the type and magnitude of local/regional stressors. From 1960 to 2010, Nevada's growth rate was the highest in the nation (www.census.gov/prod/cen2010/briefs/c2010br-01.pdf). Clark County has experienced particularly high growth, with a population increase of greater than 40 percent since the 2000 census. Factors like land ownership, historic and current land use, proximity to human and energy developments, and desirability for recreation all influence the level of human-caused stress. The strong elevation/climate gradients and large difference in the environmental characteristics of southern Nevada ecosystems (fig. 1.2; Chapter 1) have a major influence on both patterns of land use and the dominant stressors for different ecosystem types. Shifts in land use related to population growth, urbanization, and energy development and largely focused in lower elevation ecosystems including sagebursh, blackbrush and shadscale, and Mojave Desert scrub. Water divisions influence riparian/aquatic ecosystems and springs, while groundwater pumping also has the potential to affect ecosystems that characterize lower valleys including Mojave Desert scrub. Recreational uses influence all ecosystems, and wild horse and burro use and livestock grazing affect all but alpine and subalpine ecosystems. Insects and disease, as well as invasive species are widespread stressors. Fire is limited to ecosystems with sufficient fuels to carry fire and is strongly influence by invasive species in lower elevation Mojave Desert scrub, blackbrush and shadscale, and sagebursh ecosystems. This chapter address aspects of several of the Goals and Sub-goals listed in the SNAP Science Research Strategy (table 1.3; Turner and others 2009). Altered fire regimes, invasive species, land use practices, and management actions are addressed in Goal 1 -- Sustain, Restore, and Enhance Southern Nevada's Ecosystems. The effects of these stressors on sensitive species and habitat are specifically addressed in Sub-goal 1.4 -- Sustain and Enhance Southern Nevada's Biotic Communities, to Preserve Biodiversity and Maintain Populations. Anthropogenic factors, such a recreation and urbanization, are referred to in Goal 2-- Provide for Responsible Use of Southern Nevada;s Lands in a Manner that Preserve Heritage Resources and Promotes an Understanding of Human Interaction with the Landscape.

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Maintaining and restoring sustainable ecosystems in southern Nevada

Managers in southern Nevada are challenge with determining appropriate goals and objectives and developing viable approaches for maintaining and restoring sustainable ecosystems in a time of rapid socio-ecological and environmental change. Sustainable or "healthy" ecosystems supply clean air, water and habitat for a diverse array of plants and animals. As described in Chapter 1, sustainable ecosystems retain characteristic processes like hydrological flux and storage, geomorphic processes, biogeochemical cycling and storage, biological activity and productivity, and population regeneration and reproduction over the normal cycle of disturbance events (modified from Chapin and others 1996 and Christensen and others 1996). Ecological restoration of stressed or disturbed ecosystems in an integral part of managing for sustainable ecosystems. The Society of Ecological Restoration International (SERI) defines ecological restoration as the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed (SERI 2004). Many of the southern Nevada's ecosystems are being subjected to anthropogenic stressors that span global, regional, and local scales (Chapter 2)., and are crossing ecological thresholds to new alternative states (Chapter 4 and Chapter 5). These alternative states often represent novel communities with disturbance regimes that differ significantly from historic conditions. Past management and restoration goals often focused on returning ecosystems to pre-disturbance conditions (Harris and others 2006). This approach assumes stable or equilibrium conditions and ignores changes in ecosystems processes due to land uses, increases in CO 2 concentrations, and climate change. A more realistic approach is to base management and restoration goals on the current potential of an ecosystem to support a given set of ecological conditions, and on the likelihood of future change due to warming climate (Harris and others 2006). This approach requires understanding ecosystem resilience to anthropogenic disturbance and climate change, the alternative states that exist for ecosystems, and the factors that result in threshold crossing (Bestelmeyer and others 2009; Hobbs and Harris 2001; Stingham and others 2003; Whisemnant 1999). It also requires the ability to predict how climate is likely to influence ecosystems in the future (Harris and others 2006). This chapter addresses the restoration aspects of Sub-goal 1.3 in the SNAP Science Research Strategy which is to restore and sustain proper function of southern Nevada's watersheds and landscapes (able 1.3; Turner and others 2009). The effects of global, regional and local stresses on southern Nevada ecosystems are presented in Chapter 2. Here, we discuss appropriate objectives and develop guidelines for maintaining and restoring southern Nevada ecosystems. We then discuss the differences in ecological resilience to stress and disturbance and resistance to invasive species in southern Nevada ecosystems and describe restoration and management approaches for the different ecosystem types. We conclude with knowledge gaps and management implications.

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Species of conservation concern and environmental stressors: Local regional and global effects

Species conservation has traditionally been based on individual species within the context of their requisite habitat, which is generally defined as the communities and ecosystems deemed necessary for their presence. Conservation decisions are hampered by the fact that environmental stressors that poetically threaten the persistence of species can operate at organizational levels larger than the habitat or home range of a focal species. Resource managers must therefore simultaneously consider local, regional, and/or global scale stressors for effective conservation and management of species of concern. The wide ranging effects associated with global stressors such as climate change may exceed or exacerbate the effects of local or regional stressors, they still need to understand the direct and interactive effects of global stressors and ultimately how they affect the lands they manage. Conservation of species in southern Nevada is further complication by the fact that the region includes one of the largest and fastest growing urban centers in North America. To accomplish the goal of species conservation, resource managers must identify actionable management options that mitigate the effects of local and regional stressor in the context of the effects of global stressors that are beyond their control. Species conservation is typically focused on a subset often referred to as species of conservation concern that have either demonstrated considerable decline or are naturally rare or have limited distributions. Stressors can directly and indirectly impact species in a variety of ways and through a diversity of mechanisms. Some stressors have been more intense in the past (e.g., livestock grazing) whereas other are now only emerging as new stressors (e.g., solar energy development, climate change). The primary stressors affecting southern Nevada ecosystems are listed in table 2.1 and reviewed in detail in Chapter 2. This chapter addresses Dub-goal 1.4 in the SNAP Science Research Strategy which is to sustain and enhance southern Nevada's biotic communities to preserve biodiversity wand maintain viable populations (table 1.3; Turner and others 2009). We provide numerous examples of how stressors affect the range and/or habitat of select species of conservation concern. It is important to note that the species or groups discussed in this chapter by no means represent a comprehensive treatment of all species of conservation concern listed in Table 1.2 (Chapter 1). Rather, several species were chosen as examples for each southern Nevada ecosystem type to illustrate how stressors and linkages among them can affect species of conservation concern, keeping in mind that many of the species considered here are found in more than one ecosystem type. In addition, the stressors that may impact a species in one ecosystem may not be those that affect it in another ecosystem and different species in the same ecosystem may not be affected by the same suite of stressors. Finally, at the start of each ecosystem section we summarize key resource concerns, species used as examples, key stressors, and potential synergistic effects of those stressors relative to the species example.

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USGS2013

An overview of the Southern Nevada Agency Partnership science and research synthesis

Maintaining and restoring the diverse ecosystems and resources that occur in southern Nevada in the face of rapid socio-economic and ecological change presents numerous challenged to Federal land managers. Rapid population growth since the 1980s, the land uses associated with that growth, and the interactions of those uses with the generally dry and highly variable climate result in numerous stresses to ecosystems, species, and cultural resource. In addition, climate models predict that the rate of temperature increase and, thus, changes in ecological processes, will be highest for ecosystems like the Mojave Desert. The Southern Nevada Agency Partnership (SNAP; http:www.SNAP.gov) was established in 1999 to address common issues pertaining to public lands in southern Nevada. Partners include the Bureau of Land Management, National Park Service, U.S. Fish and Wildlife Service, and USDA Forest Service and they work with each other, the local community, and other partners. SNAP agencies manage more than seven million acres of public lands in southern Nevada (95% of the land area). Federal land includes two national recreation areas, two national conservation area, four national wildlife refuges, 18 congressionally designated wilderness areas, five wilderness study areas, and 22 areas of critical environmental concern. The partnership's activities are mainly centered in Southern Nevada's Clark County (fig. 1.1), but lands managed by SNAP partner agencies also include portions of Lake Mead National Recreation Area in Mohave County, Arizona, U.S. Fish and Wildlife Service, and USDA Forest Service-managed lands in Lincoln and Nye Counties, Nevada, and all lands and activities managed by the Southern Nevada District Office of the Bureau of Land Management. These lands encompass nine distinct ecosystem types (fig. 1.2), support multiple species of management concern an 17 listed species, and are rich in cultural and historic resource. This introductory executive summary discusses the Science and Research Strategy developed by the SNAP agencies, the Science and Research Report, and need for science-based management in southern Nevada.

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USGS2013

Invasive species in southern Nevada

Southern Nevada contains a wide range of topographies, elevations, and climactic zones emblematic of its position at the ecotone between the Mojave Desert, Great Basin, and Colorado Plateau ecoregions. These varied environmental conditions support a high degree of biological diversity (Chapter 1), but they also provide opportunities for a wide range of invasive species. In addition, the population center of the Las Vegas valley, and the agricultural area scattered throughout Clark, Lincoln, and Nye counties, all connected by a network of roads and highways, plus ephemeral and perennial watercourses, provide abundant opportunities for new invaders to be transported into and within southern Nevada (Brooks 2009; Brookes and Lair 2009). Invasive species are a concern for land managers because they can compete directly with native species (Brooks 2000; Chambers and others 2007; DeFlaco and others 2003, 2007; Mazzola and others 2010), change habitat conditions (Brooks and Esque 2002; Esque and others 2010; Miller and others 2011), and alter ecosystems properties (Brooks and Matchett 2006; Brooks and Pyke 2001; Evans and others 2001). Many invasive species have already established and spread to the point that they are now considered to pose significant problems in southern Nevada. However, there are likely many more than have wither not been transported to or colonized the region, or have established by for various reasons not spread or increased in abundance to the point where they have a significant impact. Land managers must understand both current and potential future problems posed by invasive species to appropriately prioritize management actions. This chapter addressed Sub-goal 1.2 in the SNAP Science Research Strategy (table 1.3; Turner and others 2009), which is to protect southern Nevada's ecosystems from the adverse impacts of invasive species. It provides a brief overview of the key concepts associated with the ecology and management of invasive species, and includes information relevant to all five strategic goals identified by the National Invasive Species Council: prevention, early detection and rapid response, control and management, restoration, and organization collaboration (National Invasive Species Council 2001, 2008). Restoration also is discussed in a broader context in Chapter 5 and 7. This chapter does not present a comprehensive review of all invasive species associated land management issues in southern Nevada, but rather uses key species of concern to illustrate invasion ecology concepts and management strategies. It is focused on terrestrial and aquatic plants and animals, and does not address potential invasive taxa from the other Kingdoms. The information presented herein is intended to provide a foundation upon which land management plans can be developed and project-level decisions can be made relative to the management of invasive species in southern Nevada.

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