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At least 595 records · Page 33Linked to original sources

USGS2018

Macroecological patterns of sexual size dimorphism in turtles of the world

Sexual size dimorphism (SSD) is a well-documented phenomenon in both plants and animals; however, the ecological and evolutionary mechanisms that drive and maintain SSD patterns across geographic space at regional and global scales are understudied, especially for reptiles. Our goal was to examine geographic variation of turtle SSD and to explore ecological and environmental correlates using phylogenetic comparative methods. We use published body size data on 135 species from nine turtle families to examine how geographic patterns and the evolution of SSD are influenced by habitat specialization, climate (annual mean temperature and annual precipitation) and climate variability, latitude, or a combination of these predictor variables. We found that geographic variation, magnitude and direction of turtle SSD are best explained by habitat association, annual temperature variance and annual precipitation. Use of semi-aquatic and terrestrial habitats was associated with male-biased SSD, whereas use of aquatic habitat was associated with female-biased SSD. Our results also suggest that greater temperature variability is associated with female-biased SSD. In contrast, wetter climates are associated with male-biased SSD compared with arid climates that are associated with female-biased SSD. We also show support for a global latitudinal trend in SSD, with females being larger than males towards the poles, especially in the families Emydidae and Geoemydidae. Estimates of phylogenetic signal for both SSD and habitat type indicate that closely related species occupy similar habitats and exhibit similar direction and magnitude of SSD. These global patterns of SSD may arise from sex-specific reproductive behaviour, fecundity and sex-specific responses to environmental factors that differ among habitats and vary systematically across latitude. Thus, this study adds to our current understanding that while SSD can vary dramatically across and within turtle species under phylogenetic constraints, it may be driven, maintained and exaggerated by habitat type, climate and geographic location.

Journal of Evolutionary Biology↗

USGS2022

Continuous water-quality and suspended-sediment transport monitoring in San Francisco Bay, California, water years 2020–21

The U.S. Geological Survey (USGS) has continuously monitored real-time water quality and suspended-sediment transport in San Francisco Bay (the Bay) since 1989 as part of a multi-agency effort (see “Acknowledgments” section) to address estuary management, water supply, and ecological concerns. The San Francisco Bay area is home to millions of people and biologically diverse marine and terrestrial flora and fauna. Freshwater mixes with saltwater in the Bay and is subject to riverine influences (floods, droughts, managed reservoir releases, and freshwater diversions) and marine influences (tides, waves, and effects of saltwater). Water temperature, salinity, suspended-sediment concentration (SSC), and turbidity, are used by State and Federal resources managers and are monitored at eight key locations throughout the Bay (fig. 1). Water temperature and salinity affect the density of water, which controls gravity-driven circulation patterns and stratification in the water column. Salinity indicates the relative mixing of fresh and ocean waters in the Bay and is derived from specific conductance measurements. Turbidity is a measure of light scattered from suspended particles in the water that is used to estimate suspended-sediment concentration. Suspended-sediment concentrations also are directly measured through depth-integrated water sampling. Suspended sediment affects Bay water quality in multiple ways. Suspended sediment affects phytoplankton growth by attenuating sunlight in the water column. Suspended sediment deposition on tidal marshes and intertidal mudflats helps to restore and sustain these habitats as sea level rises. Settling of suspended sediment in ports and shipping channels creates the need for more dredging. In addition, suspended sediment often carries adsorbed contaminants as it is transported in the water column, which affects the distributions and concentrations of adsorbed contaminants in the environment. Excessive concentrations of sediment-adsorbed contaminants in deposits on the bottom of the Bay can affect ecosystem health. External factors, such as tidal currents, waves, and wind can also affect water quality in the Bay. Tidal currents in the Bay change direction four times daily, and wind direction and intensity typically fluctuate on a daily cycle. Consequently, salinity, water temperature, and suspended-sediment concentration differ spatially and temporally throughout the Bay. Therefore, high-frequency measurements at multiple locations are needed to monitor these changes. Data collected at eight stations throughout the Bay are transmitted in near real-time using cellular telemetry and posted to the USGS National Water Information System (NWIS; https://waterdata.usgs.gov/usa/nwis ). The purposes of this fact sheet are to (1) provide information about the USGS San Francisco Bay water-quality monitoring network; (2) highlight various applications in which these data can be used; and (3) provide internet links to access the resulting continuous water-quality data collected by the USGS.

California↗

USGS1975

Water resources data for Maine, water year 1974

Water resources data for the 1974 water year for Maine including records of streamflow or reservoir storage at gaging stations, partial-record stations, and miscellaneous sites, records of water-quality data on the chemical and physical characteristics of surface- and ground-water, and records of ground-water levels in index wells are given in this report. In Part 1, records are included for 63 gaging stations, of which 62 are streamflow discharge stations, and 1 is a lake station; also are included records for 22 crest-stage partial-record stations, and 14 miscellaneous sites. In Part 2, water quality data on chemical, physical, and biological characteristics of surface and ground water were collected from designated sampling sites at predetermined intervals such as once daily, weekly, monthly, or less frequently, and at some sites data were recorded on punched paper tape at 60minute intervals. Records are given for 38 sampling stations of which 11 are continuous record stations, and 27 are miscellaneous sites. Records of chemical analyses are also given for 21 ground-water sites. In Part 3, water level data are shown for 11 ground-water wells. Locations of surface-water stations, water-quality stations, and ground-water wells are shown in figure 2. A few pertinent stations in bordering States and Provinces are also included in this report. The records were collected and computed by the Water Resources Division of the U.S. Geological Survey under the direction of G. S. Hayes, District Chief, succeeded by C. R. Wagner. These data represent that portion of the National Water Data System collected by the U.S. Geological Survey and cooperating State and Federal agencies in Maine.

Maine↗

USGS2019

Plasticity in elk migration timing is a response to changing environmental conditions

Migration is an effective behavioral strategy for prolonging access to seasonal resources and may be a resilient strategy for ungulates experiencing changing climatic conditions. In the Greater Yellowstone Ecosystem (GYE), elk are the primary ungulate, with approximately 20,000 individuals migrating to exploit seasonal gradients in forage while also avoiding energetically costly snow conditions. How climate-induced changes in plant phenology and snow accumulation are influencing elk migration timing is unknown. We present the most complete record of elk migration across the GYE, spanning 9 herds and 414 individuals from 2001 to 2017, to evaluate the drivers of migration timing and test for temporal shifts. The timing of elk departure from winter range involved a trade-off between current and anticipated forage conditions, while snow melt governed summer range arrival date. Timing of elk departure from summer range and arrival on winter range were both influenced by snow accumulation and exposure to hunting. At the GYE scale, spring and fall migration timing changed through time, most notably with winter range arrival dates becoming almost 50 days later since 2001. Predicted herd-level changes in migration timing largely agreed with observed GYE-wide changes—except for predicted winter range arrival dates which did not reflect the magnitude of change detected in the elk telemetry data. Snow melt, snow accumulation, and spring green-up dates all changed through time, with different herds experiencing different rates and directions of change. We conclude that elk migration is plastic, is a direct response to environmental cues, and that these environmental cues are not changing in a consistent manner across the GYE. The impacts of changing elk migration timing on predator–prey dynamics, carnivore–livestock conflict, disease ecology, and harvest management across the GYE are likely to be significant and complex.

Idaho, Montana, Wyoming↗

USGS2021

Applying assessments of adaptive capacity to inform natural-resource management in a changing climate

Adaptive capacity (AC)—the ability of a species to cope with or accommodate climate change—is a critical determinant of species vulnerability. Using information on species’ AC in conservation planning is key to ensuring successful outcomes. We identified connections between a list of species’ attributes (e.g., traits, population metrics, and behaviors) that were recently proposed for assessing species’ AC and management actions that may enhance AC for species at risk of extinction. Management actions were identified based on evidence from the literature, a review of actions used in other climate adaptation guidance, and our collective experience in diverse fields of global-change ecology and climate adaptation. Selected management actions support the general AC pathways of persist in place or shift in space, in response to contemporary climate change. Some actions, such as genetic manipulations, can be used to directly alter the ability of species to cope with climate change, whereas other actions can indirectly enhance AC by addressing ecological or anthropogenic constraints on the expression of a species’ innate abilities to adapt. Ours is the first synthesis of potential management actions directly linked to AC. Focusing on AC attributes helps improve understanding of how and why aspects of climate are affecting organisms, as well as the mechanisms by which management interventions affect a species’ AC and climate change vulnerability. Adaptive-capacity-informed climate adaptation is needed to build connections among the causes of vulnerability, AC, and proposed management actions that can facilitate AC and reduce vulnerability in support of evolving conservation paradigms.

Conservation Biology↗

USGS2026

21st-century mangrove expansion along the southeastern United States

Warming winter temperatures are driving range expansion of tropical, cold-sensitive mangroves into temperate ecosystems. Along the Atlantic coast of North America, the mangrove range limit is particularly sensitive to climate variability and historical data demonstrate that the mangrove-salt marsh ecotone on this coast has shifted recurrently during recent centuries. However, a comprehensive understanding of how this mangrove-salt marsh ecotone may shift in the future remains lacking. Here, we combine ensemble forecasting of mangrove distribution for the next century with high-resolution oceanographic dispersal simulations, phenological observations, and historical hurricane data to project future mangrove-salt marsh dynamics at the rapidly changing range limit in northeastern Florida (USA). We show that warming winter temperatures will drive continued poleward expansion of mangroves along North America's Atlantic coast, potentially reaching South Carolina by 2100. With ongoing climate change, suitable mangrove habitat is projected to expand beyond the current range limit, and dispersal simulations suggest successful colonization of these sites from established mangrove populations. Additionally, patterns in hurricane directionality and intensity and field reports of propagule presence reveal that these high-energy events may significantly contribute to future mangrove range expansion by facilitating long-distance, storm-driven propagule dispersal. The encroachment of mangroves in salt marsh-dominated latitudes is expected to substantially modify wetland ecosystem function and structure, emphasizing how the identification of newly colonizable habitat can inform conservation strategies and site-specific decisions on mangrove management.

Florida, Georgia, North Carolina, South Carolina↗

USGS2004

Fort Collins Science Center: Species and Habitats of Federal Interest

Ecosystem changes directly affect a wide variety of plant and animal species, floral and faunal communities, and groups of species such as amphibians and grassland birds. Appropriate management of public lands plays a crucial role in the conservation and recovery of endangered species and can be a key element in preventing a species from being listed under the Endangered Species Act. The Species and Habitats of Federal Interest Branch of the Fort Collins Science Center (FORT) conducts research on the ecology, habitat requirements, distribution and abundance, population dynamics, and genetics and systematics of many species facing threatened or endangered status or of special concern to resource management agencies. FORT scientists develop reintroduction and restoration techniques, technologies for monitoring populations, and novel methods to analyze data on population trends and habitat requirements. FORT expertise encompasses both traditional and specialized natural resource disciplines within wildlife biology, including population dynamics, animal behavior, plant and community ecology, inventory and monitoring, statistics and computer applications, conservation genetics, stable isotope analysis, and curatorial expertise.

Fact Sheet↗

USGS1999

A CALFED-supported study of the Delta’s foodweb base

Scientists from six universities and the US Geological Survey (USGS) have begun a new project to characterize the food resource which supports secondary production in different habitats of the Sacramento-San Joaquin Delta. The project is supported by CALFED Category III, USGS, and the IEP; it is designed to answer basic questions about the organic matter which supports biological production at the lowest trophic levels. We know, from the excellent long-term records of IEP agencies, that the abundance of zooplankton (especially native species) has declined dramatically in the past three decades. We do not understand the underlying mechanisms of these declines, but it is likely that they are the result of multiple, interacting stressors. One potential limitation of secondary production could be a sub-optimal food resource, manifested either as low quantity or poor nutritional quality of the available pools of organic matter. Some past studies support this possibility, especially for the case of benthic macroinvertebrates. The project was conceived to do the following: Identify the potential sources of organic matter (for example, phytoplankton, vascular plants, agricultural sources) in different habitats; Determine the relative food quality of each of these different sources for secondary producers, either directly or after microbial processing; and Assess the habitats and environmental conditions that provide the maximum food resources for secondary producers.

Interagency Ecological Program Newsletter↗

USGS2015

Effects of Hydrocarbon Extraction on Landscapes of the Appalachian Basin

An important and sometimes overlooked aspect of contemporary natural gas exploration, development, and delivery activities is the geographic profile and spatial footprint that these activities have on the land surface. The function of many ecosystems and the goods and services they provide, in large part, are the result of their natural spatial arrangement on the landscape. Shale-gas development can create alterations to the pattern of land use and land cover, and represents a specific form of land use and land cover change that can substantially impact critical aspects of the spatial pattern, form, and function of landscape interactions, including many biological responses. The need for energy resources has created numerous economic opportunities for hydrocarbon extraction in the Appalachian basin. The development of alternative energy natural gas resources from deep-shale drilling techniques, along with conventional natural gas extraction methods, has created a flurry of wells, roads, pipelines, and related infrastructure across many parts of the region. An unintended and sometimes overlooked consequence of these activities is their effect on the structure and function of the landscape and ecosystems. The collective effect of over 100,000 hydrocarbon extraction permits for oil, coal bed methane, Marcellus and Utica Shale natural gas wells, and other types of hydrocarbon gases and their associated infrastructure has saturated much of the landscape and disturbed the natural environment in the Appalachian basin. The disturbance created by the sheer magnitude of the development of these collective wells and infrastructure directly affects how the landscape and ecosystems function and how they provide ecological goods and services.

New York, Ohio, Pennsylvania, Virginia, West Virgi↗

USGS2013

Water temperatures in select nearshore environments of the Colorado River in Grand Canyon, Arizona, during the Low Steady Summer Flow experiment of 2000

Water releases from Glen Canyon Dam, Arizona, are the primary determinant of streamflow, sediment transport, water quality, and aquatic and riparian habitat availability in the Colorado River downstream of the dam in Grand Canyon. The presence and operation of the dam have transformed the seasonally warm Colorado River into a consistently cold river because of hypolimnetic, or deep-water, releases from the penstock withdrawal structures on the dam. These releases have substantially altered the thermal regime of the downstream riverine environment. This, in turn, has affected the biota of the river corridor, particularly native and nonnative fish communities and the aquatic food web. In the spring and summer of 2000, a Low Steady Summer Flow experiment was conducted by the U.S. Geological Survey and the Bureau of Reclamation to evaluate the effects of the experimental flow on physical and biological resources of the Colorado River ecosystem downstream from Glen Canyon Dam to Lake Mead on the Arizona-Nevada border. This report describes the water temperatures collected during the experimental flow from 14 nearshore sites in the river corridor in Grand Canyon to assess the effects of steady releases on the thermal dynamics of nearshore environments. These nearshore areas are characterized by low-velocity flows with some degree of isolation from the higher velocity flows in the main channel and are hypothesized to be important rearing environments for young native fish. Water-temperature measurements were made at 14 sites, ranging from backwater to open-channel environments. Warming during daylight hours, relative to main-channel temperatures, was measured at all sites in relation to the amount of isolation from the main-channel current. Boat traffic, amount of direct solar radiation, and degree of isolation from the main-channel current appear to be the primary factors affecting the differential warming of the nearshore environment.

Arizona↗

USGS2023

Where can managers effectively resist climate-driven ecological transformation in pinyon-juniper woodlands of the US Southwest?

Pinyon–juniper (PJ) woodlands are an important component of dryland ecosystems across the US West and are potentially susceptible to ecological transformation. However, predicting woodland futures is complicated by species-specific strategies for persisting and reproducing under drought conditions, uncertainty in future climate, and limitations to inferring demographic rates from forest inventory data. Here, we leverage new demographic models to quantify how climate change is expected to alter population demographics in five PJ tree species in the US West and place our results in the context of a climate adaptation framework to resist, accept, or direct ecological transformation. Two of five study species, Pinus edulis and Juniperus monosperma , are projected to experience population declines, driven by both rising mortality and decreasing recruitment rates. These declines are reasonably consistent across various climate futures, and the magnitude of uncertainty in population growth due to future climate is less than uncertainty due to how demographic rates will respond to changing climate. We assess the effectiveness of management to reduce tree density and mitigate competition, and use the results to classify southwest woodlands into areas where transformation is (a) unlikely and can be passively resisted, (b) likely but may be resisted by active management, and (c) likely unavoidable, requiring managers to accept or direct the trajectory. Population declines are projected to promote ecological transformation in the warmer and drier PJ communities of the southwest, encompassing 37.1%–81.1% of our sites, depending on future climate scenarios. Less than 20% of sites expected to transform away from PJ have potential to retain existing tree composition by density reduction. Our results inform where this adaptation strategy could successfully resist ecological transformation in coming decades and allow for a portfolio design approach across the geographic range of PJ woodlands.

Arizona, Colorado, New Mexico, Utah↗

USGS2011

Birth seasonality and offspring production in threatened neotropical primates related to climate

Given the threatened status of many primate species, the impacts of global warming on primate reproduction and, consequently, population growth should be of concern. We examined relations between climatic variability and birth seasonality, offspring production, and infant sex ratios in two ateline primates, northern muriquis, and woolly monkeys. In both species, the annual birth season was delayed by dry conditions and El Niño years, and delayed birth seasons were linked to lower birth rates. Additionally, increased mean annual temperatures were associated with lower birth rates for northern muriquis. Offspring sex ratios varied with climatic conditions in both species, but in different ways: directly in woolly monkeys and indirectly in northern muriquis. Woolly monkeys displayed an increase in the proportion of males among offspring in association with El Niño events, whereas in northern muriquis, increases in the proportion of males among offspring were associated with delayed onset of the birth season, which itself was related, although weakly, to warm, dry conditions. These results illustrate that global warming, increased drought frequency, and changes in the frequency of El Niño events could limit primate reproductive output, threatening the persistence and recovery of ateline primate populations.

Global Change Biology↗

USGS2000

Cruise report R/V Surf Surveyor cruise S1-00-CL, mapping the bathymetry of Crater Lake, Oregon

During the Spring of 1999, the US Geological Survey (USGS) Pacific Seafloor Mapping Project (PSMP) was contacted by the US National Park Service Crater Lake National Park (CLNP) to inquire about the plausibility of producing a high-resolution multibeam bathymetric map of Crater Lake. The purpose was to generate a much higher-resolution and more geographically accurate bathymetric map than was produced in 1959, the last time the lake had been surveyed. Scientific interest in various aspects of Crater Lake (aquatic biology, geochemistry, volcanic processes, etc.) has increased during the past decade but the basemap of bathymetry was woefully inadequate. Funds were gathered during the early part of 2000 and the mapping began in late July, 2000. Crater Lake (see fig. 1 in report) is located in south central Oregon (see fig. 2 in report) within the Cascades Range, a chain of volcanoes that stretches from northern California to southern British Columbia. Crater Lake is the collapsed caldera of Mt. Mazama from a climatic eruption about 7700-yr ago (Nelson et al., 1988; Bacon and Lanphere, 1990; Bacon et al., 1997). The floor of Crater Lake has only been mapped three times since the lake was first stumbled upon by gold prospectors in the 1853. The first survey was carried by out by William G. Steel during a joint USGS-US Army expedition under the direction of Maj. Clarence E. Dutton in 1886 (Dutton, 1889). Steelï¿½s mapping survey collected 186 soundings using a Millers lead-line sounding machine (see fig.3 in report). The resulting map (see fig.4 in report) shows only soundings and no attempts were made to generate contours. The second survey, conducted in 1959 by the US Coast and Geodetic Survey, mapped the bathymetry of Crater Lake with an acoustic echo sounder using radar navigation and collected 4000 soundings. The data were contoured by Williams (1961) and Byrne (1962) and the result is a fairly detailed map of the large-scale features of Crater Lake (see fig. 5 in report). The third mapping survey, the one of this report, was a joint USGS-NPS project carried out under a Cooperative Agreement with the Center for Coastal and Ocean Mapping, University of New Hampshire. The 2000 survey used a Kongsberg Simrad EM1002 high-resolution multibeam mapping system owned and operated by C&C Technologies, Inc. of Lafayette, LA.

Oregon↗

USGS2016

Ecological requirements for pallid sturgeon reproduction and recruitment in the Missouri River—A synthesis of science, 2005 to 2012

This report is intended to synthesize the state of the scientific understanding of pallid sturgeon ecological requirements to provide recommendations for future science directions and context for Missouri River restoration and management decisions. Recruitment of pallid sturgeon has been low to non-existent throughout its range. Emerging understanding of the genetic structure of pallid sturgeon populations sets a broad framework for species and river management decisions, including decisions about managing the future genetic diversity of the species, but also decisions about where and what type of river restoration actions will be effective for subpopulations of this highly migratory species. Adult pallid sturgeon may migrate hundreds of kilometers (km) to spawn and their progeny may disperse even greater distances downstream as drifting free embryos. As a result of their complex life history pallid sturgeon naturally exploit a wide range of habitats during their life cycles. The construction of dams and reservoirs has fragmented habitats and may have shifted Missouri River subpopulations downstream. Research has not identified one primary biological or ecological constraint that appears to limit populations of the pallid sturgeon. With the present (2013) state of knowledge many life stages and life-stage transitions cannot be ruled out as contributing to recruitment failure. Biological opinions in 2000 (and amended in 2003) presented the dominant hypotheses for recruitment failure that existed at that time. Emphasis was on the role of the flow regime, specifically spring flow pulses (“spring rises”), to condition spawning substrate and cue reproductive aggregations and migrations, and on low flows and additional slow, shallow-water area to serve as rearing habitat for age-0 to juvenile pallid sturgeon. Studies on spawning habitat dynamics have documented that habitat patches selected for spawning by fish in the Lower Missouri River (Missouri River downstream from Gavins Point Dam to the confluence with the Mississippi River) are dominantly on outside, revetted bends in the deepest, fastest, and most turbulent water. Studies in more natural habitat on the Yellowstone River have documented spawning in convergent flow in the middle of the channel on discrete patches of gravel within a sand-dominated channel, an arrangement that may be more effective in attracting aggregations of reproductive fish compared to the nearly continuous revetment on the Lower Missouri River. Pallid sturgeon spawn in the spring and early summer during periods of increasing day length. Water temperature consistently exerts a threshold effect for spawning at 16–18 °C. In addition, the role of water temperature is indicated by pauses and reversals in upstream migrations that have been associated with cold weather fronts that create a transient decrease in water temperature. From 2005 to 2012 on the Lower Missouri River, no obvious relations between flow pulses and fish movements and spawning behaviors have been apparent. However, pallid sturgeon tracking at the Upper Missouri–Yellowstone confluence indicates that in most years, most telemetered pallid sturgeon migrate out of the Missouri River and into the Yellowstone River in the June–July timeframe in association with the spring pulse. This pattern was disrupted in 2011 when a high flow pulse with warm temperatures and high turbidity emanated from the Milk River, followed by record releases from Fort Peck Dam, and 36–39 percent of the telemetered population migrated up the Upper Missouri. This result supports the hypothesis that sufficiently large flow pulses may trigger migration and aggregation but it is not clear that functional pulses are within reservoir management authorities. Notably, a pallid sturgeon free embryo was captured on the Upper Missouri River in 2011 and another single, genetically confirmed embryo was captured on the Yellowstone River in 2012. Research on free-embryo drift has indicated the potential for hundreds of miles of downstream dispersal. Lack of distance to accommodate the extended downstream dispersal period of free embryos on the Upper Missouri and Yellowstone Rivers is the predominant hypothesis for recruitment failure in the upper basin. Long drift distances in the Lower Missouri River may be responsible for shifting Lower Missouri River sub-populations further into the Middle Mississippi River. Physical understanding of drift processes indicates that mean velocities could be slowed through decreased discharges or increased channel hydraulic radius (width and topographic diversity) to reduce free-embryo dispersal distances. In addition, the probability that free embryos are transported into and retained in channel-margin habitats is theoretically amenable to channel re-engineering that would increase cross-channel secondary currents in bends or channel expansions. Considerable uncertainty persists, however, about whether extended drift of Lower Missouri River larvae is responsible for recruitment failure. If drift distance is limiting, it is important to discern whether it would be advisable to retain larvae within the Missouri River, and where along the river restoration projects should be placed to optimize survival and growth of age-0 and juvenile sturgeon. Longitudinal differences in female pallid sturgeon fecundity lend support to the hypothesis that recruitment failure may be due, in part, to fish having insufficient nutrition to produce the numbers of gametes needed for the population to grow, perhaps because of simultaneous declines in prey-fish populations and their habitats. Establishing a chain of causality from habitat decline, to prey-fish populations, to sturgeon diets, to sturgeon fecundity, and to pallid sturgeon population growth presents a considerable scientific challenge. In addition to the dominant hypotheses relating pallid sturgeon populations to changes in flow regime and channel morphology, other factors have been identified that might be sources of stress and contribute to recruitment failure. Among these are water quality and contaminants. Ambient water-quality monitoring on the Missouri River has demonstrated summer episodes when dissolved oxygen dips below 5 milligrams per liter, a threshold that may be stressful especially to age-0 and juvenile sturgeon. Documented cases of intersex in shovelnose and pallid sturgeon indicate that agricultural and municipal sources of endocrine disrupting chemicals also may have a role in pallid sturgeon recruitment failure. Scientific understanding of the ecological requirements of pallid sturgeon has increased almost exponentially in the last two decades, and efforts are now turning from understanding fundamental biology of the species to quantifying how population dynamics relate to potential management actions. Progress in developing the science needed to inform management actions on the Missouri River may benefit from continuation of monitoring of reproductive cycles, reproductive movements, growth, and survival of telemetry tagged adults, increased emphasis on focused, complementary field and laboratory studies of factors influencing early life history, implementation of studies to resolve the role of food limitations in growth, survival, and reproductive condition, and implementation of studies designed specifically to parameterize models linking management to populations.

Missouri River↗

USGS2021

Prioritizing restoration areas to conserve multiple sagebrush-associated wildlife species

Strategic restoration of altered habitat is one method for addressing worldwide biodiversity declines. Within the sagebrush steppe of western North America, habitat degradation has been linked to declines in many species, making restoration a priority for managers; however, limited funding, spatiotemporal variation in restoration success, and the need to manage for diverse wildlife species make decision-making regarding restoration actions challenging. To address the challenge of spatial conservation prioritization, we developed the Prioritizing Restoration of Sagebrush Ecosystems Tool (PReSET). This decision support tool utilizes the prioritizr package in program R and an integer linear programming algorithm to select parcels representing both high biodiversity value and high probability of restoration success. We tested PReSET on a sagebrush steppe system within southwestern Wyoming using distributional data for six species with diverse life histories and a spatial layer of predicted sagebrush recovery times to identify restoration targets at both broad and local scales. While the broad-scale portion of our tool outputs can inform policy, the local-scale results can be applied directly to on-the-ground restoration. We identified restoration priority areas with greater precision than existing spatial prioritizations and incorporated range differences among species. We noted tradeoffs, including that restoring for habitat connectivity may require restoration actions in areas with lower probability of success. Future applications of PReSET will draw from emerging datasets, including spatially-varying economic costs of restoration, animal movement data, and additional species, to further improve our ability to target effective sagebrush restoration.

Wyoming↗

USGS2015

Shorebird migration in the face of climate change: potential shifts in migration phenology and resource availability

Changes in temperature and seasonality resulting from climate change are heterogeneous, potentially altering important sources of natural selection acting on species phenology. Some species have apparently adapted to climate change but the ability of most species to adapt remains unknown. The life history strategies of migratory animals are dictated by seasonal factors, which makes these species particularly vulnerable to heterogeneous changes in climate and phenology. Here, we examine the phenology of migratory shorebirds, their habitats, and primary food resources, and we hypothesize how climate change may affect migrants through predicted changes in phenology. Daily abundance of shorebirds at stopover sites was correlated with local phenology and peaked immediately prior to peaks in invertebrate food resources. A close relationship between migrant and invertebrate phenology indicates that shorebirds may be vulnerable to changes in seasonality driven by climate change. It is possible that shifts in migrant and invertebrate phenology will be congruent in magnitude and direction, but because migration phenology is dependent on a suite of ecological factors, any response is likely to occur at a larger temporal scale and may lag behind the response of invertebrate food resources. The resulting lack of sufficient access to food at stopover habitats may cause migrants to extend migration and have cascading effects throughout their life cycle. If the heterogeneous nature of climate change results in uneven changes in phenology between migrants and their prey, it may threaten the long-term viability of migratory populations

South Dakota↗

USGS1998

Instability of development and fractal architecture in dryland plants as an index of grazing pressure

Developmental instability has been used to monitor the well-being of natural populations exposed to physical, chemical and biological stressors. Here, we use developmental instability to assess the impact of grazing on Chrysothamnus greenii and Seriphidium novum shrubs, and Oryzopsis hymenoides grass, common in the arid intermountain west of the U.S.A. Statistical noise in allometric relations was used as an indicator of developmental instability arising from grazing-induced stress. Unpalatable species that are not grazed ( Chrysothamnus greenii ) or species that are dormant during the winter–spring grazing period ( Oryzopsis hymenoides ) show lower allometric variability under high grazing pressure. Palatable species ( Seriphidium novum ) exhibit high developmental instability under low and high grazing pressure. Grazing pressure imposed by presumably co-adapted wild herbivores enhances developmental stability in species habituated to moderate grazing, like Oryzopsis hymenoides , but stresses plants such as Chrysothamnus greenii that prefer disturbed environments. These grazing effects are probably due to the impact grazing has on competitive relationships and not to the direct action of the herbivore on the plants.

Journal of Arid Environments↗

USGS2010

Microbial community shifts influence patterns in tropical forest nitrogen fixation

The role of biodiversity in ecosystem function receives substantial attention, yet despite the diversity and functional relevance of microorganisms, relationships between microbial community structure and ecosystem processes remain largely unknown. We used tropical rain forest fertilization plots to directly compare the relative abundance, composition and diversity of free-living nitrogen (N)-fixer communities to in situ leaf litter N fixation rates. N fixation rates varied greatly within the landscape, and 'hotspots' of high N fixation activity were observed in both control and phosphorus (P)-fertilized plots. Compared with zones of average activity, the N fixation 'hotspots' in unfertilized plots were characterized by marked differences in N-fixer community composition and had substantially higher overall diversity. P additions increased the efficiency of N-fixer communities, resulting in elevated rates of fixation per nifH gene. Furthermore, P fertilization increased N fixation rates and N-fixer abundance, eliminated a highly novel group of N-fixers, and increased N-fixer diversity. Yet the relationships between diversity and function were not simple, and coupling rate measurements to indicators of community structure revealed a biological dynamism not apparent from process measurements alone. Taken together, these data suggest that the rain forest litter layer maintains high N fixation rates and unique N-fixing organisms and that, as observed in plant community ecology, structural shifts in N-fixing communities may partially explain significant differences in system-scale N fixation rates.

Oecologia↗