Vegetation Characteristics of Mountain and Wyoming Big Sagebrush Plant Communities in the Northern Great Basin

Dominant plant species are often used as indicators of site potential in forest and rangelands. However, subspecies of dominant vegetation often indicate different site characteristics and, therefore, may be more useful indicators of plant community potential and provide more precise information for management. Big sagebrush (Artemisia tridentata Nutt.) occurs across large expanses of the western United States. Common subspecies of big sagebrush have considerable variation in the types of sites they occupy, but information that quantifies differences in their vegetation characteristics is lacking. Consequently, wildlife and land management guidelines frequently do not differentiate between subspecies of big sagebrush. To quantify vegetation characteristics between two common subspecies of big sagebrush, we sampled 106 intact big sagebrush plant communities. Half of the sampled plant communities were Wyoming big sagebrush (A. tridentata subsp. wyomingensis [Beetle & A. Young] S. L. Welsh) plant communities, and the other half were mountain big sagebrush (A. tridentata subsp. vaseyana [Rydb.] Beetle) plant communities. In general, mountain big sagebrush plant communities were more diverse and had greater vegetation cover, density, and biomass production than Wyoming big sagebrush plant communities. Sagebrush cover was, on average, 2.4-fold higher in mountain big sagebrush plant communities. Perennial forb density and cover were 3.8- and 5.6-fold greater in mountain compared to Wyoming big sagebrush plant communities. Total herbaceous biomass production was approximately twofold greater in mountain than Wyoming big sagebrush plant communities. The results of this study suggest that management guidelines for grazing, wildlife habitat, and other uses should recognize widespread subspecies as indicators of differences in site potentials.     

Restoration of Sagebrush in Crested Wheatgrass Communities: Longer-Term Evaluation in Northern Great Basin

Crested wheatgrass (Agropyron cristatum [L] Gaertm. and Agropyron desertorum [Fisch.] Schult.), an introduced bunchgrass, has been seeded on millions of hectares of sagebrush steppe. It can establish near-monocultures; therefore, reestablishing native vegetation in these communities is often a restoration goal. Efforts to restore native vegetation assemblages by controlling crested wheatgrass and seeding diverse species mixes have largely failed. Restoring sagebrush, largely through planting seedlings, has shown promise in short-term studies but has not been evaluated over longer timeframes. We investigated the reestablishment of Wyoming big sagebrush (Artemisia tridentata spp. wyomingensis [Beetle & A. Young] S.L. Welsh) in crested wheatgrass communities, where it had been broadcast seeded (seeded) or planted as seedlings (planted) across varying levels of crested wheatgrass control with a herbicide (glyphosate) for up to 9 yr post seeding/planting. Planting sagebrush seedlings in crested wheatgrass stands resulted in full recovery of sagebrush density and increasing sagebrush cover over time. Broadcast seeding failed to establish any sagebrush, except at the highest levels of crested wheatgrass control. Reducing crested wheatgrass did not influence density, cover, or size of sagebrush in the planted treatment, and therefore, crested wheatgrass control is probably unnecessary when using sagebrush seedlings. Herbaceous cover and density were generally less in the planted treatment, probably as a result of increased competition from sagebrush. This trade-off between sagebrush and herbaceous vegetation should be considered when developing plans for restoring sagebrush steppe. Our results suggest that planting sagebrush seedlings can increase the compositional and structural diversity in near-monocultures of crested wheatgrass and thereby improve habitat for sagebrush-associated wildlife. Planting native shrub seedlings may be a method to increase diversity in other monotypic stands of introduced grasses.     

Herbicide-Assisted Restoration of Great Basin Sagebrush Steppe Infested With Medusahead and Downy Brome

Downy brome or cheatgrass (Bromus tectorum) and medusahead (Taeniatherum caput-medusae) are the most problematic invasive annual grasses in rangelands of the western United States, including sagebrush communities that provide habitat to sage grouse. Rehabilitation of infested sites requires effective weed control strategies combined with seeding of native plants or desirable competitive species. In this study, we evaluated the effect of three fall-applied pre-emergence herbicides (imazapic, rimsulfuron, and chlorsulfuron + sulfometuron), and one spring-applied postemergence herbicide (glyphosate) on the control of downy brome and medusahead and the response of seeded perennial species and resident vegetation in two sagebrush communities in northeastern California. All pre-emergence treatments gave > 93% control of both invasive species at both sites in the first year. Glyphosate was less consistent, giving > 94% control at one site and only 61% control of both species at the other site. Imazapic was the only herbicide to maintain good control (78–88%) of both species 2 yr after treatment. No herbicide caused detectible long-term damage to either perennial grasses or annual forbs, and imazapic treatment resulted in an increase in resident native forb cover 3 yr after treatment. Broadcast seeding with or without soil incorporation did not result in successful establishment of perennial species, probably due to below-average precipitation in the year of seeding. These results indicate that several chemical options can give short-term control of downy brome and medusahead. Over the course of the study, imazapic provided the best management of both invasive annual grasses while increasing native forb cover.     

Effects of Sagebrush Restoration and Conifer Encroachment on Small Mammal Diversity in Sagebrush Ecosystem

Conifer encroachment in sagebrush ecosystems reduces habitat heterogeneity, niche space, and resource availability, all of which negatively affect many wildlife populations. Sagebrush restoration is recommended as a management action to mitigate conifer encroachment and restore wildlife across millions of hectares in the Great Basin. Despite this recommendation, the effects of conifer encroachment and sagebrush restoration are unknown for most wildlife species. Small nonvolant mammal communities include keystone species, consumers and prey; facilitate energy flow and ecological function; and provide important ecological goods and services. We assessed causal relationships between conifer encroachment and sagebrush restoration (conifer removal and seeding native plants) on small mammal communities over 11 yr using a Before-After-Control–Impact design. Sagebrush habitat supported an additional small mammal species, twice the biomass, and nearly three times higher densities than conifer-encroached habitat. Sagebrush restoration increased shrub cover, decreased tree cover, and density but failed to increase native herbaceous plant density. Restoration caused a large increase in the non-native, invasive annual cheatgrass (Bromus tectorum L.). Counter to prediction, small mammal diversity did not increase in response to sagebrush restoration, but restoration maintained small mammal density in the face of ongoing conifer encroachment. Piñon mice (Peromyscus truei), woodland specialists with highest densities in conifer-encroached habitat, were negatively affected by sagebrush restoration. Increasing cheatgrass due to sagebrush restoration may not negatively impact small mammal diversity, provided cheatgrass density and cover do not progress to a monoculture and native vegetation is maintained. The consequences of conifer encroachment, a long-term, slow-acting impact, far outweigh the impacts of sagebrush restoration, a short-term, high-intensity impact, on small mammal diversity. Given the ecological importance of small mammals, maintenance of small mammal density is a desirable outcome for sagebrush restoration.     

Land-Use Legacies and Vegetation Recovery 90 Years After Cultivation in Great Basin Sagebrush Ecosystems

Agricultural land use is known to alter ecological processes, and native plant communities can require decades to centuries to recover from the disturbance of cultivation. “Recovery” is typically measured by comparison to undisturbed adjacent sites as a control. Recovery following cultivation in sagebrush ecosystems of the Great Basin remains largely unexamined even though nearly a half million hectares of land were dry-farmed and abandoned in the early 1900s. We tested the hypothesis that the native vegetation has not recovered from this exotic disturbance by evaluating differences in canopy cover of shrubs, grasses, and forbs between paired sets of historically dry-farmed land and adjacent never-cultivated areas. Paired sites were located in three ecological sites in northwestern Utah. We found that vegetation recovery from cultivation is variable by growth form, species, and ecological site. Shrub recovery was different among sagebrush (Artemisia) species. Yellow rabbitbrush (Chrysothamnus viscidiflorus [Hook.] Nutt.) and black greasewood (Sarcobatus vermiculatus [Hook.] Torr.), which often increase following disturbance, maintained higher cover inside old fields. At one of the paired sets, shrub composition was altered from a mix of four species to dominance of mainly Wyoming big sagebrush (Artemisia tridentata Nutt. subsp. wyomingensis Beetle & Young). Total forb cover was generally lower in cultivated areas and some species, such as spiny phlox (Phlox hoodii Richardson), had not recovered. The most common grass species encountered across all ecological sites, bottlebrush squirreltail (Elymus elymoides [Raf.] Swezey), had higher cover in cultivated areas. Surprisingly, exotic annual species, such as cheatgrass (Bromus tectorum L.), did not dominate these sites as they have for decades after cultivation in other areas of the Great Basin. This study demonstrates that the land-use legacy of dry farming on vegetation remains nearly a century after cultivation has ceased, and has direct implications for describing ecological site conditions.     

Ecosystem Water Availability in Juniper versus Sagebrush Snow-Dominated Rangelands

Western Juniper (Juniperus occidentalis Hook.) has greatly expanded in the past 150 + years and now dominates over 3.6 million ha of rangeland in the Intermountain Western United States. The impacts of juniper encroachment on critical ecohydrological relationships among snow distribution, water budgets, plant community transitions, and habitat requirements for wildlife, such as the greater sage grouse (Centrocercus urophasianus), remain poorly understood. The goal of this study is to better understand how juniper encroachment affects water availability for ecohydrologic processes and associated wildlife habitat in snow-dominated sagebrush (Artemisia spp.) steppe ecosystems. A 6-yr combined measurement and modeling study is conducted to explore differences in snow distribution, water availability, and annual water balances between juniper-dominated and sagebrush-dominated catchments. Although there is large interannual variability in both measured weather data and modeled hydrologic fluxes during the study, results indicate that juniper-dominated catchments have greater peak accumulations of snow water equivalent, earlier snow melt, and less streamflow relative to sagebrush-dominated catchments. Water delivery is delayed by an average of 9 days in the sagebrush-dominated scenario compared with the juniper-dominated scenario as a result of increased water storage in snow drifts. The delayed water input to sagebrush-dominated ecosystems in typical water years has wide-ranging implications for available surface water, soil water, and vegetation dynamics associated with wildlife habitat for sagebrush obligates such as sage grouse. Results from this study imply that the retention of high-elevation, sagebrush-dominated landscapes may become crucial for sage grouse habitat management if mid- and low-elevation precipitation continues to transition from snow to rain dominated.     

Acceptance,Acceptability, and Trust for Sagebrush Restoration Options in the Great Basin: A Longitudinal Perspective

In surveys of residents in three urban and three rural locations in the Great Basin we examined the social acceptability of six management practices showing promise for restoring sagebrush-dominated rangelands. Unlike most studies of range management perceptions that have relied on single measurements, we used longitudinal data from a questionnaire mailed in 2006 to residents that were resurveyed in 2010. Overall, 698 respondents comprised the panel. Respondents' self-reported levels of knowledge about the health and management of Great Basin rangelands decreased from 2006 to 2010. In both years, mean acceptance was greater for the use of prescribed fire, grazing, felling, and mowing, but relatively low for chaining and herbicide use. Overall, acceptability ratings were similar in 2006 and 2010 but individually about half of the acceptance responses differed between years. Practices were more acceptable to respondents who expressed greater concern about threats posed by inaction, except that the threat of wildfire was negatively associated with acceptance for prescribed burning. Acceptance was not significantly related to concern about overall health of Great Basin rangelands, or to self-reported knowledge level. Rural/urban residence and general attitudes toward environmental protection were sometimes influential, but more so in 2006 than in 2010. By far the best predictor of acceptance was trust in agencies' ability to implement the practice. In both years respondents were more likely to judge a practice acceptable than to trust agencies to use the practice. Positive or negative change in trust level was the most significant predictor of change in acceptability judgment from 2006 to 2010. Results suggest that efforts to increase acceptance of practices among Great Basin stakeholders should focus on activities designed to build trust rather than simply providing more or better information.     

Validating a Time Series of Annual Grass Percent Cover in the Sagebrush Ecosystem

We mapped yearly (2000–2016) estimates of annual grass percent cover for much of the sagebrush ecosystem of the western United States using remotely sensed, climate, and geophysical data in regression-tree models. Annual grasses senesce and cure by early summer and then become beds of fine fuel that easily ignite and spread fire through rangeland systems. Our annual maps estimate the extent of these fuels and can serve as a tool to assist land managers and scientists in understanding the ecosystem’s response to weather variations, disturbances, and management. Validating the time series of annual maps is important for determining the usefulness of the data. To validate these maps, we compare Bureau of Land Management Assessment Inventory and Monitoring (AIM) data to mapped estimates and use a leave-one-out spatial assessment technique that is effective for validating maps that cover broad geographical extents. We hypothesize that the time series of annual maps exhibits high spatiotemporal variability because precipitation is highly variable in arid and semiarid environments where sagebrush is native, and invasive annual grasses respond to precipitation. The remotely sensed data that help drive our regression-tree model effectively measures annual grasses’ response to precipitation. The mean absolute error (MAE) rate varied depending on the validation data and technique used for comparison. The AIM plot data and our maps had substantial spatial incongruence, but despite this, the MAE rate for the assessment equaled 12.62%. The leave-one-out accuracy assessment had an MAE of 8.43%. We quantified bias, and bias was more substantial at higher percent cover. These annual maps can help management identify actions that may alleviate the current cycle of invasive grasses because it enables the assessment of the variability of annual grass ? percent cover distribution through space and time, as part of dynamic systems rather than static systems.     

Aboriginal Precedent for Active Management of Sagebrush-Perennial Grass Communities in the Great Basin

Until recently, most contemporary ecologists have ignored or diminished anecdotal historical accounts and anthropologists' reports about aboriginal fire in the Great Basin. Literature review shows that Indians practiced regular use of fire for many purposes, including the obvious reasons of increasing the availability of desired plants, maintaining habitats for animals used as food, and driving game during hunts. Historical accounts of prehistoric anthropogenic firing, inferences from fire-scar data, and data regarding annual production capability of representative sagebrush (Artemisia spp.)-perennial grass ecological sites indicate that prehistoric conditions were neither fuel- nor ignition-limited. According to many sources, this “active management” by Indians was widespread, significant, and more common than lightning-caused fires, resulting in mosaic vegetation patterns that subsequently moderated the behavior of “natural fires.” This interaction between Indian-burning and lightning fires may have strongly influenced the pre-Euro-American settlement vegetation of the Great Basin. At the very least, the landscape was a patchwork of areas altered by aboriginal people and areas shaped primarily by bio-physical processes. Based on this prehistoric precedent, current historically unprecedented conditions (fuel load and exotic weed invasion threats), and predicted climate change, contemporary active management of sagebrush-perennial grass communities is paramount. Restoration measures should be scientifically based and tailored to achieve ecological resilience and functionality in specific sites. Prescribed fire is not always ecologically appropriate or judicious, especially in Wyoming big sagebrush (A. tridentata spp. wyomingensis) communities, so managers should consider using other alternatives where an intentional low severity distubance is deemed necessary. Properly planned active management would disrupt fuel continuity for lighthning fires, ensure ecological process and successional integrity, and benefit multiple uses on a landscape scale.     

Biophysical Factors and Canopy Coupling Control Ecosystem Water and Carbon Fluxes of Semiarid Sagebrush Ecosystems

The sagebrush-steppe ecosystem covers much of western North America, and its productivity is sensitive to warming and increasingly variable precipitation. Interannual variation in precipitation has been shown to be the most significant factor controlling biogeochemical cycling while both soil and atmospheric drought are dominant factors of ecosystem fluxes. We show that plant canopies can also act to limit water losses through stomatal and aerodynamic control. We use 4 data-yr from 2 sites (2 069 and 2 469 m above sea level elevation, respectively) to evaluate control of carbon and water fluxes and to calculate the degree to which the ecosystem canopy and atmosphere are decoupled. Environmental conditions were similar between the two sites, although the lower elevation site was slightly warmer (1.8°C higher temperature) and drier (0.2 kPa higher vapor pressure deficit). Ecosystem responses of net ecosystem exchange (NEE) and evapotranspiration (ET) to environmental drivers were similar between sites and years, with the wet site-yr 2009 having the largest ET and NEE fluxes. Canopy leaf area led to divergent behavior of the canopy-atmosphere decoupling parameter under high (> 11% by volume) soil moisture conditions. During low (< 11%) soil moisture periods, both sites had tight ecosystem stomatal control on ET with little NEE activity. This study highlights how semiarid ecosystems can alter their canopy leaf area in order to control how decoupled semi-arid canopies are to the atmosphere, potentially moderating impacts of climate change.     

Influence of Ecosystem Services on Management Decisions by Public Land Ranchers in the Intermountain West,United States

Ecosystem services are benefits humans obtain as a result of ecosystem processes and conditions. In the western United States, public rangelands are managed for a spectrum of ecosystem services on behalf of multiple stakeholders. Decisions of ranchers who hold public land grazing allotments must balance operational needs for forage with societal expectations for other ecosystem services. To better understand their choices regarding ecosystem services, we interviewed ranchers to learn about the bases for their management decisions and identify services they believe rangelands provide. A total of 19 services were identified, many of which reflected ranchers’ recognition that they manage within the context of a broader social-ecological system (e.g., maintaining open space). We then conducted a mail survey of Bureau of Land Management grazing permittees in six states to understand the importance they personally place on different services, as well as the extent to which they manage with those services in mind. Fourteen of the 19 ecosystem services identified in interviews were reported by at least 50% of the survey sample (N = 435) as influencing their management decisions. Most respondents reported trying to manage deeded and leased land to the same standard. Aside from forage for livestock (ranked #1), ranchers were less likely to report managing for provisioning services than for cultural, supporting, and regulating services. Importance ratings for ecosystem services followed a similar pattern, although there were a few differences in rank order. Ranchers tended to report managing for more ecosystem services if they had larger operations, earned at least 50% of their income from ranching, spent more time out on the ranch, and relied on multiple sources for information about range management. Results indicate public land ranchers believe they are managing for multifunctionality, balancing their own operational needs with those of society.     

Climate-Driven Interannual Variability in Net Ecosystem Exchange in the Northern Great Plains Grasslands

The Northern Great Plains grasslands respond differently under various climatic conditions; however, there have been no detailed studies investigating the interannual variability in carbon exchange across the entire Northern Great Plains grassland ecosystem. We developed a piecewise regression model to integrate flux tower data with remotely sensed data and mapped the 8-d and 500-m net ecosystem exchange (NEE) for the years from 2000 to 2006. We studied the interannual variability of NEE, characterized the interannual NEE difference in climatically different years, and identified the drought impact on NEE. The results showed that NEE was highly variable in space and time across the 7 yr. Specifically, NEE was consistently low (?35 to 322 g C·m^?2·yr^?1) with an average annual NEE of ?2 ± 242 g C·m^?2·yr^?1 and a cumulative flux of ?152 g C·m^?2. The Northern Great Plains grassland was a weak source for carbon during 2000–2006 because of frequent droughts, which strongly affected the carbon balance, especially in the Western High Plains and Northwestern Great Plains. Comparison of the NEE map with a drought monitor map confirmed a substantial correlation between drought and carbon dynamics. If drought severity or frequency increases in the future, the Northern Great Plains grasslands may become an even greater carbon source.     

Public Perceptions of Significant Wildlife in Hyogo,Japan

Public perceptions of wildlife vary by species, context, and culture. Understanding these perceptions helps managers understand how their decisions may generate conflict among stakeholders. We mailed questionnaires to residents in the northern region of Hyogo prefecture in Japan to examine their willingness to tolerate wildlife species of greatest concern to government officials, including: (a) native species frequently causing agricultural damage (wild boar [Sus scrofa], sika deer [Cervus nippon], Japanese macaque [Macaca fuscata]), (b) vulnerable species (Asiatic black bear [Ursus thibetanus]), (c) endangered species (reintroduced oriental white stork [Ciconia boyciana]), and (d) non-native, invasive species (nutria [Myocastor coypus]). We used the Potential for Conflict Index (PCI₂) to analyze our data, and found that respondents’ (n?=?868) acceptance was highest for the endangered oriental white stork and lowest for the non-native nutria. These perceptions also varied with sociodemographic characteristics, including a significant negative relationship between age and willingness to have boar, deer, macaque, bears, and nutria nearby.     

Postfire Seeding and Plant Community Recovery in the Great Basin

As wildland fire frequency increases around the globe, a better understanding of the patterns of plant community recovery in burned landscapes is needed to improve rehabilitation efforts. We measured establishment of seeded species, colonization of Bromus tectorum and other nonnative annual plants, and recovery of nonseeded native species in topographically distinct areas within five fires that burned Great Basin shrub-steppe communities in Elko County, Nevada. Plant density, frequency, and cover data were collected annually for 4 yr postfire. Vegetation composition varied among flat areas and north- and south-facing aspects, and changed over the course of the sampling period; recovery varied among sites. In general, B. tectorum densities were higher on south aspects, particularly 3 and 4 yr after fire, when densities increased dramatically relative to prefire conditions. Nonseeded native perennial grasses, forbs, and shrubs were abundant in three of the five fire sites, and were more likely to be present on north aspects and flat areas. Over time, nonseeded perennial grass densities remained relatively constant, and nonseeded forbs and shrubs increased. Seeded species were most likely to establish in flat areas, and the density of seeded perennial grasses, forbs, and shrubs decreased over time. Frequency and density measurements were highly correlated, especially for perennial species. Our results emphasize the value of considering site aspect and the potential for native regrowth when planning and monitoring restorations. For example, effective rehabilitation of south aspects may require the development of new restoration methods, whereas north aspects and flat areas in sites with a strong native component were not improved by the addition of seeded species, and may require weed control treatments, rather than reseeding, to improve recovery. Tailoring revegetation objectives, seed mixes, seeding rates, and monitoring efforts to conditions that vary within sites may lead to more cost effective and successful restoration.     

Basalt Milkvetch Responses to Novel Restoration Treatments in the Great Basin

The restoration of native forbs in the Great Basin and similar dryland ecosystems remains a great challenge for land managers. Variable soil water, precocious germination and emergence, and the presence of soil fungal pathogens often reduce plant establishment. Novel restoration treatments that increase soil water during early forb life stages, delay germination and emergence to coincide with favorable spring conditions, and reduce mortality from soil fungal pathogens may benefit native forb restoration. We compared the efficacy of three novel treatments—snow fencing, plant protection fabric, and seed coatings—to improve establishment of a forb species native to the Great Basin, basalt milkvetch (Astragalus filipes Torr. ex A. Gray). We replicated treatments plus a no-treatment control at three sites in the Great Basin in a randomized complete block design over 2 yr. To evaluate the efficacy of our restoration treatments, we measured germination, seedling emergence, establishment, and second-yr survival. The effects of snow fencing and plant protection fabric varied by site and life stage and were likely influenced by the wet spring conditions across sites, particularly the two northern sites. Snow fencing increased establishment and second-yr survival at one site. Plant protection fabric did not benefit any life stage at any site. Seed coatings increased seedling emergence at all sites but did not affect establishment or survival. Overall, second-yr survival remained low across all sites and treatments. Our study indicates that our treatments can positively affect basalt milkvetch emergence, establishment, and survival, but additional management actions are needed to improve long-term restoration success of native forbs.