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Steven T. Knick

Publications and source records attributed to Steven T. Knick.

At least 37 records · Page 2Linked to original sources
USGS2011

Connecting pattern and process in greater sage-grouse populations and sagebrush landscapes

Abstract. Spatial patterns influence the processes that maintain Greater Sage-Grouse (Centrocercus urophasianus) populations and sagebrush (Artemisia spp.) landscapes on which they depend. We used connectivity analyses to: (1) delineate the dominant pattern of sagebrush landscapes; (2) identify regions of the current range-wide distribution of Greater Sage-Grouse important for conservation; (3) estimate distance thresholds that potentially isolate populations; and (4) understand how landscape pattern, environmental disturbance, or location within the spatial network influenced lek persistence during a population decline. Long-term viability of sagebrush, assessed from its dominance in relatively unfragmented landscapes, likely is greatest in south-central Oregon and northwest Nevada; the Owyhee region of southeast Oregon, southwest Idaho, and northern Nevada; southwest Wyoming; and south-central Wyoming. The most important leks (breeding locations) for maintaining connectivity, characterized by higher counts of sage-grouse and connections with other leks, were within the core regions of the sage-grouse range. Sage-grouse populations presently have the highest levels of connectivity in the Wyoming Basin and lowest in the Columbia Basin Sage-Grouse management zones (SMZs). Leks separated by distances 13-18 km could be isolated due to decreased probability of dispersals from neighboring leks. The range-wide distribution of sage-grouse was clustered into 209 separate components (units in which leks were interconnected within but not among) when dispersal was limited to distances 18 km. The most important components for maintaining connectivity were distributed across the central and eastern regions of the range-wide distribution. Connectivity among sage-grouse populations was lost during population declines from 1965-1979 to 1998-2007, most dramatically in the Columbia Basin SMZ. Leks that persisted during this period were larger in size, were more highly connected, and had lower levels of broad-scale fire and human disturbance. Protecting core regions and maintaining connectivity with more isolated sage-grouse populations may help reverse or stabilize the processes of range contraction and isolation that have resulted in long-term population declines.

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USGS2011

Preface

No abstract available.

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USGS2011

Influences of environmental and anthropogenic features on greater sage-grouse populations, 1997-2007

The Greater Sage-Grouse (Centrocercus urophasianus), endemic to western North Amer-ica, is of great conservation interest. Its popula-tions are tracked by spring counts of males at lek sites. We explored the relations between trends of Greater Sage-Grouse lek counts from 1997 to 2007 and a variety of natural and anthropogenic fea-tures. We found that trends were correlated with several habitat features, but not always similarly throughout the range. Lek trends were positively associated with proportion of sagebrush (Artemisia spp.) cover, within 5 km and 18 km. Lek trends had negative associations with the coverage of agriculture and exotic plant species. Trends also tended to be lower for leks where a greater pro-portion of their surrounding landscape had been burned. Few leks were located within 5 km of developed land and trends were lower for those leks with more developed land within 5 km or 18 km. Lek trends were reduced where communi-cation towers were nearby, whereas no effect of power lines was detected. Active oil or natural gas wells and highways, but not secondary roads, were associated with lower trends. Effects of some anthropogenic features may have already been manifested before our study period and thus not have been detected in this analysis. Results of this range-wide analysis complement those from more intensive studies on smaller areas. Our findings are important for identifying features that could threaten Greater Sage-Grouse populations.

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USGS2011

Ecological influence and pathways of land use in sagebrush

Land use in sagebrush (Artemisia spp.) landscapes influences all sage-grouse (Centrocer-cus spp.) populations in western North America. Croplands and the network of irrigation canals cover 230,000 km2 and indirectly influence up to 77% of the Sage-Grouse Conservation Area and 73% of sagebrush land cover by subsidizing synanthropic predators on sage-grouse. Urbanization and the demands of human population growth have created an extensive network of con-necting infrastructure that is expanding its influence on sagebrush landscapes. Over 2,500 km 2 are now covered by interstate highways and paved roads; when secondary roads are included, 15% of the Sage-Grouse Conservation Area and 5% of existing sagebrush habitats are 2.5 km from roads. Density of secondary roads often exceeds 5 km/km 2 , resulting in widespread motorized access for recreation, creating extensive travel corridors for management actions and resource development, subsidizing predators adapted to human presence, and facilitating spread of exotic or invasive plants. Sagebrush lands also are being used for their wilderness and recreation values, including off highway vehicle use. Approximately 12,000,000 animal use months (AUM amount of forage to support one livestock unit per month) are permitted for grazing livestock on public lands in the western states. Direct effects of grazing on sage-grouse populations or sagebrush landscapes are not possible to assess from current data. However, management of lands grazed by livestock has influenced sagebrush ecosystems by vegetation treatments to increase forage and reduce sagebrush and other plant species unpalatable to livestock. Fences (2 km/km 2 in some regions), roads, and water developments to manage livestock movements further modify the landscape. Oil and gas development influences 8% of the sagebrush habitats with the highest intensities occurring in the eastern range of sage-grouse; 20% of the sagebrush distribution is indirectly influenced in the Great Plains, Wyoming Basin, and Colorado Plateau SMZs. Energy development physically removes habitat to construct well pads, roads, power lines, and pipelines; indirect effects include habitat fragmentation, soil disturbance, and facilitation of exotic plant and animal spread. More recent development of alternative energy, such as wind and geothermal, creates infrastructure in new regions of the sage-grouse distribution. Land use will continue to be a dominant stressor on sage-brush systems; its individual and cumulative effects will challenge long-term conservation of sage-grouse populations.

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USGS2011

Conservation of greater sage-grouse- a synthesis of current trends and future management

Recent analyses of Greater Sage-Grouse (Centrocercus urophasianus) populations indicate substantial declines in many areas but relatively stable populations in other portions of the species? range. Sagebrush (Artemisia spp.) habitats neces-sary to support sage-grouse are being burned by large wildfires, invaded by nonnative plants, and developed for energy resources (gas, oil, and wind). Management on public lands, which con-tain 70% of sagebrush habitats, has changed over the last 30 years from large sagebrush control projects directed at enhancing livestock grazing to a greater emphasis on projects that often attempt to improve or restore ecological integrity. Never-theless, the mandate to manage public lands to provide traditional consumptive uses as well as recreation and wilderness values is not likely to change in the near future. Consequently, demand and use of resources contained in sagebrush land-scapes plus the associated infrastructure to sup-port increasing human populations in the western United States will continue to challenge efforts to conserve Greater Sage-Grouse. The continued widespread distribution of sage-grouse, albeit at very low densities in some areas, coupled with large areas of important sagebrush habitat that are relatively unaffected by the human footprint, sug-gest that Greater Sage-Grouse populations may be able to persist into the future. We summarize the status of sage-grouse populations and habitats, provide a synthesis of major threats and chal-lenges to conservation of sage-grouse, and suggest a roadmap to attaining conservation goals.

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USGS2011

Preface

Explore the source record for details and available documents.

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USGS2011

Chapter 2: Sagebrush-associated species of conservation concern

Selection of species of concern is a critical early step in conducting broad-scale ecological assessments for conservation planning and management. Many criteria can be used to guide this selection, such as conservation status, existing knowledge base, and association with plant communities of interest. In conducting the Wyoming Basins Ecoregional Assessment (WBEA), we followed a step-wise process to select vascular plant and vertebrate species of concern. Based on our selection process, we identified 65 taxa of sagebrush-associated ( Artemisia spp.) vascular plants of conservation concern. The vast majority were forbs, and nearly all are found in Wyoming (n = 59; 91%), reflecting its central location and spatial dominance (51%) of the study area. Forty-eight plants (74%) were ranked either S1 or S2 (state-level ranks indicating imperilment due to rarity, threats, or other factors) in at least one state within the assessment area. Forty vertebrates of concern were selected for our assessment, including 17 mammals, 18 birds, and 4 reptiles. Among these were 7 vertebrates commonly considered sagebrush-obligate species: sagebrush lizard ( Sceloporus graciosus ), greater sage-grouse ( Centrocercus urophasianus ), sage thrasher ( Oreoscoptes montanus ), sage sparrow ( Amphispiza belli ), Brewer’s sparrow (S pizella breweri ), pronghorn ( Antilocapra americana ), and pygmy rabbit ( Brachylagus idahoensis ). Several vertebrate species of concern in the Wyoming Basins are either rare or imperiled, including black-footed ferret ( Mustela nigripes ) and Wyoming pocket gopher ( Thomomys clusius ).

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USGS2011

Chapter 3: Changes to the Wyoming Basins landscape from oil and natural gas development

Oil and natural gas have been produced in Wyoming since the late 1800s although the rate of extraction has increased substantially in the last two decades. Well pads, roads, and infrastructure built to support resource development alter native vegetation configuration; however, the rate and effect of land cover change resulting from oil and gas extraction has not been quantified across the region. We used a Geographic Information System (GIS) to model development through time and assess change to native vegetation at two spatial extents (field and subbasin) within the Wyoming portion of the Wyoming Basins Ecoregional Assessment (WBEA) area. Since 1900, a minimum of 1,703 km 2 of native vegetation in the WBEA area has been replaced by well pads or roads. Shrublands were, and continue to be, the dominant land cover class and the cover type most affected by oil and gas extraction. Average shrubland patch size has decreased by approximately 10% at the subbasin extent in the WBEA. Core area (≥60 m from edge) size declined by 13% as road development fragmented formerly continuous patches. To date, the majority of land cover change has occurred in formally identified oil and gas fields, which cover about 1% of the WBEA in Wyoming. Approximately 7.5% of shrubland within oil and gas fields has been converted to well pad or a road supporting a well, and shrubland patch size has declined by 45%. Resource reserves, especially natural gas, have been identified outside traditional fields, and development will likely expand as resource development becomes more cost-effective. Revegetation guidelines are in place for development areas addressed by Environmental Impact Assessments although no quantitative data are available to assess how well restoration efforts are restoring landscapes and connecting fragments.

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USGS2011

Chapter 4: A sampling and analytical approach to develop spatial distribution models for sagebrush-associated species

Understanding multi-scale floral and faunal responses to human land use is crucial for informing natural resource management and conservation planning. However, our knowledge on how land use influences sagebrush (Artemisia spp.) ecosystems is limited primarily to site-specific studies. To fill this void, studies across large regions are needed that address how species are distributed relative to type, extent, and intensity of land use. We present a study design for the Wyoming Basin Ecoregional Assessment (WBEA) to sample sagebrush-associated flora and fauna along a land cover-human land use gradient. To minimize field costs, we sampled various taxonomic groups simultaneously on transects (ungulates and lagomorphs), point counts (song birds), and area-searches of 7.29-ha survey blocks (pellet counts, burrow counts, reptile surveys, medium-sized mammals, ant mounds, rodent trapping, and vegetation sampling of native and exotic plants). We then present an exploratory approach to develop species occurrence and abundance models when a priori model building is not an option. Our study design has broad applications for large-scale evaluations of arid ecosystems.

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Chapter 5: Greater sage-grouse: General use and roost site occurrence with pellet counts as a measure of relative abundance

Greater sage-grouse ( Centrocercus urophasianus ) have been declining both spatially and numerically throughout their range because of anthropogenic disturbance and loss and fragmentation of sagebrush ( Artemisia spp.) habitats. Understanding how sage-grouse respond to these habitat alterations and disturbances, particularly the types of disturbances and extent at which they respond, is critical to designing management actions and prioritizing areas of conservation. To address these needs, we developed statistical models of the relationships between occurrence and abundance of greater sage-grouse and multi-scaled measures of vegetation, abiotic, and disturbance in the Wyoming Basins Ecoregional Assessment (WBEA) area. Sage-grouse occurrence was strongly related to the amount of sagebrush within 1 km for both roost site and general use locations. Roost sites were identified by presence of sage-grouse fecal pellet groups whereas general use locations had single pellets. Proximity to anthropogenic disturbance including energy development, power lines, and major roads was negatively associated with sage-grouse occurrence. Models of sage-grouse occurrence correctly predicted active lek locations with >75% accuracy. Our spatially explicit models identified areas of high occurrence probability in the WBEA area that can be used to delineate areas for conservation and refine existing conservation plans. These models can also facilitate identification of pathways and corridors important for maintenance of sage-grouse population connectivity.

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Chapter 6: Detectability adjusted count models of songbird abundance

Sagebrush ( Artemisia spp.) steppe ecosystems have experienced recent changes resulting not only in the loss of habitat but also fragmentation and degradation of remaining habitats. As a result, sagebrush-obligate and sagebrush associated songbird populations have experienced population declines over the past several decades. We examined landscape-scale responses in occupancy and abundance for six focal songbird species at 318 survey sites across the Wyoming Basins Ecoregional Assessment (WBEA) area. Occupancy and abundance models were fit for each species using datasets developed at multiple moving window extents to assess landscape-scale relationships between abiotic, habitat, and anthropogenic factors. Anthropogenic factors had less influence on species occupancy or abundance than abiotic and habitat factors. Sagebrush measures were strong predictors of occurrence for sagebrush-obligate species, such as Brewer’s sparrows ( Spizella breweri ), sage sparrows ( Amphispiza belli ) and sage thrashers ( Oreoscoptes montanus ), as well as green-tailed towhees ( Pipilo chlorurus ), a species associated with mountain shrub communities. Occurrence for lark sparrows ( Chondestes grammacus ) and vesper sparrows ( Pooecetes gramineus ), considered shrub steppe-associated species, was also related to big sagebrush communities, but at large spatial extents. Although relationships between anthropogenic variables and occurrence were weak for most species, the consistent relationship with sagebrush habitat variables suggests direct habitat loss and not edge or additional fragmentation effects are causing declines in the avifauna examined in the WBEA area. Thus, natural and anthropogenic disturbances that result in loss of critical habitats are the biggest threats to these species. We applied our models spatially across the WBEA area to identify and prioritize key areas for conservation.

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Chapter 7: Occurrence and abundance of ants, reptiles, and mammals

Sagebrush ( Artemisia spp.)- associated wildlife are threatened by habitat loss and fragmentation and by impacts associated with anthropogenic disturbances, including energy development. Understanding how species of concern as well as other wildlife including insects, reptiles, and mammals respond to type and spatial scale of disturbance is critical to managing future land uses and identifying sites that are important for conservation. We developed statistical models to describe species occurrence or abundance, based on area searches in 7.29-ha survey blocks, across the Wyoming Basins Ecoregional Assessment (WBEA) area for six shrub steppe-associated species: harvester ant ( Pogonomyrmex spp.), thatch ant ( Formica spp.), short-horned lizard ( Phrynosoma hernandesi ), white-tailed jackrabbit ( Lepus townsendii ), cottontail ( Sylvilagus spp.) and least chipmunk ( Tamius minimus ). We modeled patterns in occupancy or abundance relative to multi-scale measures of vegetation type and pattern, abiotic site characteristics, and anthropogenic disturbance factors. Sagebrush habitat was a strong predictor of occurrence for shorthorned lizards and white-tailed jackrabbits, but weak for the other four species. Vegetation and abiotic characteristics were strong determinants of species occurrence, although the scale of response was not consistent among species. All species, with the exception of the short-horned lizard, responded to anthropogenic disturbance, although responses again varied as a function of scale and direction (negative and positive influences). Our results improve our understanding of how environmental and anthropogenic factors affect species distributions across the WBEA area and facilitate a multi-species approach to management of this sagebrush ecosystem.

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Chapter 8: Occurrence of large and medium-sized mammals: Occurrence but not count models predict pronghorn distribution

Management of medium to large-sized terrestrial mammals (Antilocapridae, Canidae, Cervidae, Leporidae, Mustelidae, Ochotonidae) in the western United States is multifaceted and complex. Species in this group generally are charismatic and provide economic opportunities, although others are considered a nuisance at one extreme or are listed as species of conservation concern at the other. Understanding the relative influence of land cover, habitat fragmentation, and human land use on their distribution during the breeding season is imperative to inform management decisions on land use and conservation planning for these species. We surveyed medium to large-sized sagebrush ( Artemisia spp.)-associated mammal species in 2005 and 2006 on 141 random transects (mean length = 1.1 km) in the Wyoming Basins, an area undergoing rapid land cover transformation due to human actions including energy development. Overall, we observed 10 species but only obtained enough observations of pronghorn ( Antilocapra americana ) to develop spatially explicit distribution models. For pronghorn, occurrence related positively to proportion of sagebrush land cover within 0.27 km, mixed shrubland land cover within 3 km, riparian land cover within 5 km, Normalized Difference Vegetation Index (NDVI) within 0.27 km, road density within 5 km, and decay distance to power line corridors at 1 km, but negatively to salt-desert shrubland cover within 18 km and an interaction between sagebrush and NDVI within 0.27 km. We found excellent predictive capability of this model when evaluated with independent test data. The model provides a basis for assessing the effects of proposed development on pronghorn and can aid planning efforts to avoid or mitigate adverse effects on pronghorn.

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Chapter 9: Occurrence of small mammals: Deer mice and challenge of trapping across large spatial extents

Small mammal communities living in sagebrush ( Artemisia spp. ) may be sensitive to habitat isolation and invasion by exotic grass species. Yet there have been no spatially explicit models to improve our understanding of landscape-scale factors determining small mammal occurrence or abundance. We live-trapped small mammals at 186 locations in the Wyoming Basin Ecoregional Assessment area to develop species distribution (habitat) models for each species. Most small mammal species (n = 14) were trapped at a only few locations. As a result, we developed a small mammal model only for the deer mouse ( Peromyscus maniculatus ). Deer mice were associated with areas having moderately productive habitat as measured by Normalized Difference Vegetation Index (NDVI), increased grassland land cover, contagion of sagebrush land cover, and proximity to intermittent water. The proportion of big sagebrush ( Artemisia tridentata ) within 0.27 km, proportion of mixed shrubland within 5 km, soil clay content, and proximity to pipelines were inversely related to the occurrence of deer mice. Understanding habitat characteristics for deer mice helps our overall understanding of the ecological processes within sagebrush habitats because deer mice act as predator, prey, competitor, and disease reservoir. Development of the empirical data necessary for spatially explicit habitat modeling of small mammal distributions at large spatial extents requires an extensive trapping effort in order to obtain enough observations to construct models, calculate robust detectability estimates, and overcome issues such as trap shyness and population cycling.

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Chapter 10: Occurrence of non-native invasive plants: The role of anthropogenic features

The invasion of non-native plants in the Wyoming Basins Ecoregional Assessment (WBEA) area is a major economic and ecological stress, with invasions thought to be hastened by energy developments. Given the potential impacts of nonnative invasive plants and the rapid changes in land use in the WBEA, broad-scale assessments and predictive models of nonnative invasive plant distribution are needed. Using this information, the current extent of populations for targeting treatment and monitoring can be identified, the habitat affinities for forecasting where weeds may establish next determined, and the responses to individual human disturbances (such as energy developments) predicted. To address these needs, we conducted vegetation surveys across the WBEA area at 317 individual survey blocks (five plots per survey block) during the summers of 2005 and 2006. Survey blocks were stratified by both human disturbance and habitat productivity; in each of five plots per survey block the occurrence of 23 common nonnative invasive plants was recorded during early and late season surveys. Here, we report on the four most common invasive plants, crested wheatgrass ( Agropyron cristatum ), cheatgrass ( Bromus tectorum ), halogeton ( Halogeton glomeratus ), and Russian thistle ( Salsola spp. ). Occurrence models were generated for each species using random-effects logistic regression to account for nesting of plots within sample sites. Predictors of occupancy included local habitat, abiotic condition, and distance to anthropogenic features. Although occurrences of all four invasive plants were affected by habitat, abiotic, and anthropogenic factors, cheatgrass and Russian thistle were most strongly associated with anthropogenic disturbance, primarily major roads and energy well sites. We assessed relationships between environmental and anthropogenic predictors and species occurrences to identify the major factors affecting current species distribution, examined shape of the response in occurrence in relation to proximity to individual anthropogenic disturbances, and provided spatial predictions of the locations where invasive plants are most likely to occur.

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Chapter 11: Management considerations

We conducted an ecoregional assessment of sagebrush ( Artemisia spp. ) ecosystems in the Wyoming Basins and surrounding regions (WBEA) to determine broad-scale species-environmental relationships. Our goal was to assess the potential influence from threats to the sagebrush ecosystem on associated wildlife through the use of spatially explicit occurrence and abundance models. These models were developed using information from field surveys conducted along gradients of vegetation productivity and human disturbance integrated with spatial datasets delineating land cover, topography, and human land use in the WBEA area. Our evaluation included all sagebrush-associated wildlife species across multiple taxa whose habitat requirements and distributions were appropriate for modeling and interpretation at the broad scales of this assessment. Dominant land uses were included in delineating the human footprint. Although overall levels of the cumulative human footprint were generally low across the WBEA area, oil and gas activities have decreased the amount of shrubland habitats and increased fragmentation within development regions over the last century. At the scale of this assessment, the influence of humans was primarily expressed as an indirect function through actions that altered or reduced available habitat. We identified 65 plant species of conservation concern; 28 of 40 vertebrate species associated with sagebrush were species of concern in at least one state. We modeled environmental relationships for 15 wildlife species from data collected from surveys conducted in 2005 and 2006 designed to sample multiple species and taxa along land cover and land use gradients across the WBEA area. Occurrence of 3 species was negatively influenced by human features; anthropogenic features were a positive influence for 3 species, 8 had a mixed response, and 1 had no measurable relationship. Sagebrush land cover, considered in all wildlife models, was important to most species but differed among species in the proportion of sagebrush required and at what spatial extent. For most species examined, the spatial extent at which sagebrush cover influenced the probability of occupancy was much larger than an individual’s home range size. Exotic plants were strongly associated with human features, particularly roads, which may function as linear vectors to facilitate spread of exotic plants across the WBEA area. We used coarse-grained spatial and thematic data because of the large spatial extent (350,000 km 2 ) of the WBEA area and the need for a consistent land cover map for the region. Distributions of species occurrence or abundance mapped in this assessment need to be corroborated with information on population demographics. In addition, our results should be interpreted relative to assumptions inherent in broad-scale ecoregional assessments. Our assessment provides managers with extensive and detailed maps of occurrence and abundance, allowing for status assessments of native species, diversity and richness, natural communities, and ecological systems present within the Wyoming Basins.

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Introduction: An ecoregional assessment of the Wyoming Basins

The Wyoming Basins Ecoregional Assessment (WBEA) area in the western United States contains a number of important land cover types, including nearly one-fourth of the sagebrush ( Artemisia spp.) in North America. Although relatively unappreciated until recent decades, the broad open landscapes dominated by sagebrush communities have received increasing attention for their ecological value and the resources that they contain (Knick and Connelly 2011). As many as 350 wildlife species depend on sagebrush ecosystems for all or part of their life requirements (Wisdom et al. 2005a). Within the WBEA, intact sagebrush landscapes provide an important stronghold for populations of greater sage-grouse ( Centrocercus urophasianus ), recently listed as a candidate species under the Endangered Species Act (U.S. Department of the Interior 2010). Numerous other plant and vertebrate species of state or national concern also occur within the WBEA study area (Ch. 2). Conserving sagebrush ecosystems is a major conservation challenge that will require an understanding not only of current trajectories and scales of habitat change due to natural and anthropogenic disturbances (Leu and Hanser 2011), but also the potential exacerbation of these trends from climate change (Wiens and Bachelet 2010, Miller et al. 2011).

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