Disturbed Alpine Ecosystems: Seedling Establishment of Early and Late Seral Dominant Species

This study examined the effects of seedbed and seedling environment on establishment of early and late seral dominant alpine species. Species studied included late seral dominant forbs (Geum rossii, Artemisia scopulorum, and Polemonium viscosum), early seral dominant forbs (Potentilla diversifolia and Sibbaldia procumbens), a late seral dominant grass (Festuca idahoensis), and early seral dominant grasses (Calamagrostis purpurascens and Deschampsia cespitosa). Germination responses of each species to wet vs. dry cold stratification and light vs. dark conditions were investigated. No statistical differences were observed in the seed germination of early and late seral dominant forbs or early and late seral dominant grasses, but significant differences were observed in the responses of grasses and forbs. Seed germination of forbs was greater under light than dark conditions and following wet cold storage. Effects of fertilization on growth responses and nutrient uptake of G. rossii and D. cespitosawere evaluated in a factorial greenhouse experiment in which seedlings of each species were grown at four levels of nitrogen (N) and phosphorous (P). The late seral dominant forb responded more like a species from a low-nutrient environment exhibiting lower relative growth rates, higher root:shoot ratios, and a smaller response to N than the early seral dominant. A field experiment on the Beartooth Plateau, Montana, examined the soil environment and seedling emergence, growth, and survival of seeded early and late seral dominants on loamy sand soils of a severe disturbance and on peat soils of an undisturbed area during two growing seasons. Effects of fertilizer and mulch were examined on the severely disturbed area. Differences between uncleared turf and turf cleared of vegetation (gap disturbance) were evaluated on the undisturbed area. The gap disturbance had higher levels of N and P and warmer soil than the severe disturbance or vegetated undisturbed area. Soil water potentials were never low enough to result in plant stress. Seedling growth was slow - .005 g to .04 g dry weight the first growing season and .02 g to .20 g the second growing season. Growth was greatest on the gap disturbance and on fertilized plots of the severely disturbed area. Early seral dominants had the largest seedlings and the smallest R/R+S ratios. Mortality was low - odds of .50 were rarely exceeded even after two years. Survival was higher on warm, nutrient rich soils of the gap disturbance. Mulch increased emergence and survival on the severe disturbance. Fertilization increased mortality, probably because an initial pulse of N was followed by a rapid decline. Higher mortality occurred in 1986 than 1985 as 1986 had a shorter growing season and cooler air and soil temperatures early in the growing season

Archiving of data on occurrence of breeding birds associated with fire treatments and controls

Since 2001, we have collected data on occupancy and relative abundance of Greater Sage- Grouse (Centrocercus urophasianus) and other species of breeding birds in the central Great Basin, and characterized the vegetation structure and composition of breeding birds’ habitats, through four projects supported by the Joint Fire Science Program (00-2-15, 01B-3-3-01, 05-2-1- 94, and 09-1-08-4). These projects collectively have generated dozens of refereed publications, dozens of invited papers or presentations, multiple M.S. theses and Ph.D. dissertations, and many workshops and field tours. Bird data included in refereed publications to date were based on point counts with a fixed radius of 75 or 100 m and a duration of 5 minutes per visit. These data previously were archived with the USDA Forest Service’s Research Data Archive. Since 2004, however, we also have conducted 100-m fixed-radius point counts with a duration of 8 minutes per visit. Furthermore, starting in 2002, we recorded birds detected beyond the fixed radius and during travel among point-count locations or at other times of day or night. We archived data on the incidental and longer-distance detections of birds, which included more than 22,600 records. We also archived all data on vegetation structure and the composition of dominant trees and shrubs collected through 2012. There are few sets of long-term, spatially extensive data on distributions and abundance of fauna or extensive characterizations of vegetation in the Great Basin. These data have considerable capacity to inform understanding and management of fire dynamics; changes in land cover, including conversion of native vegetation to cheatgrass (Bromus tectorum); and the status of species proposed for listing under the Endangered Species Act

Operationalizing Ecological Resilience Concepts for Managing Species and Ecosystems at Risk

This review provides an overview and integration of the use of resilience concepts to guide natural resources management actions. We emphasize ecosystems and landscapes and provide examples of the use of these concepts from empirical research in applied ecology. We begin with a discussion of definitions and concepts of ecological resilience and related terms that are applicable to management. We suggest that a resilience-based framework for management facilitates regional planning by providing the ability to locate management actions where they will have the greatest benefits and determine effective management strategies. We review the six key components of a resilience-based framework, beginning with managing for adaptive capacity and selecting an appropriate spatial extent and grain. Critical elements include developing an understanding of the factors influencing the general and ecological resilience of ecosystems and landscapes, the landscape context and spatial resilience, pattern and process interactions and their variability, and relationships among ecological and spatial resilience and the capacity to support habitats and species. We suggest that a spatially explicit approach, which couples geospatial information on general and spatial resilience to disturbance with information on resources, habitats, or species, provides the foundation for resilience-based management. We provide a case study from the sagebrush biome that illustrates the use of geospatial information on ecological and spatial resilience for prioritizing management actions and determine effective strategies

Effects of Spring Prescribed Fire in Expanding Pinyon-Juniper Woodlands on Seedling Establishment of Sagebrush Species

Pinyon and juniper trees are expanding into mountain sagebrush communities throughout their ranges. Fire is used to restore these sagebrush communities, but limited information is available on seedling establishment of native shrubs and herbs. We examined effects of spring prescribed fire in the Great Basin on emergence and survival of five species (Artemisia tridentata vaseyana, Festuca idahoensis, Poa secunda, Eriogonum umbellatum and Lupinus argenteus) common to these communities. Data were collected in three microsites (undertree, undershrub and interspace) on a burned and unburned site following a prescribed fire and on the unburned site the year prior to the fire. Soil temperature and moisture were collected on both sites and years. Emergence and survival of A. tridentata was low. Grasses had higher emergence and survival under trees in 2003 in the unburned site, reflecting the pre-burn distribution of these species. E. umbellatum had high emergence and survival regardless of site or microsite. L. argenteus had moderate emergence that was lowest on the burned site under trees and highest on the unburned site in interspaces. Burned soils were warmer than unburned soils. Undertree microsites on the unburned site were cooler than other microsites on both sites due to shading and insulation by needle mats. Soil moisture was generally higher on the burn site due to fewer shrubs and trees. Pinyon appeared to have a facilitative role for grass seedling establishment on both sites. Spring prescribed fire did not have a negative impact on emergence or survival in these mountain sagebrush communities. Low establishment of some species indicate higher seeding rates or repeated seeding may be required. Keywords: Great Basin, sagebrush ecosystems, restoration, revegetation, seedling emergence and survival, microenvironmental condition

Editorial: Operationalizing the Concepts of Resilience and Resistance for Managing Ecosystems and Species at Risk

Ecological resilience is essential for maintaining ecosystem services in an era of rapid global change, but successful attempts to operationalize it for managing ecosystems at risk have been limited. Clear formulation and application of ecological resilience concepts can guide ecosystem management so that it enhances the capacity of ecosystems to resist and recover from disturbances and provides adaptive space for periods of ecological reorganization. As originally defined, ecological resilience measures the amount of perturbation required to change an ecosystem from one set of processes and structures to a different set of processes and structures, or the amount of disturbance that a system can withstand before it shifts into a new regime or alternative stable state (Holling, 1973). In applied ecology, ecological resilience is increasingly used to evaluate the capacity of ecosystems to absorb, persist, and adapt to inevitable and often unpredictable change, and to use that information to determine the most effective management strategies (e.g., Chambers et al., 2014; Curtin and Parker, 2014; Pope et al., 2014; Seidl et al., 2016). As the scale and magnitude of ecological change increases, operationalizing ecological resilience for ecosystem management becomes ever more important. To date, much of the literature on ecological resilience has focused on theory, definitions, and broad conceptualizations (e.g., Gunderson, 2000; Folke et al., 2004, 2010; Walker et al., 2004; Folke, 2006; Gunderson et al., 2010). Much of the more applied research has focused on the importance of species diversity and species functional attributes in affecting responses to stress and disturbance (e.g., Pope et al., 2014; Angeler and Allen, 2016; Baho et al., 2017; Roberts et al., 2018). Recent, interdisciplinary research demonstrates that information on the relationships between an ecosystem’s environmental characteristics (climate, topography, soils, and potential biota) and its response to stress and disturbance provides a viable mechanism for assessing ecosystem resilience and relative risks (Chambers et al., 2014; Hessburg et al., 2016; Cushman et al., 2017; Kaszta et al., 2019). Approaches have been developed that enable application of resilience concepts at the scales needed for effective management of ecosystems experiencing progressive and deleterious change. For example, in the sagebrush biome of the western U.S. the concepts of resilience to fire and resistance to non-native invasive annual grasses have recently been used in an interagency framework to enhance conservation and restoration and help prevent listing of greater sage-grouse (Centrocercus urophasianus) under the Endangered Species Act (Chambers et al., 2017). In ecosystems around the globe, levels of ecological stress and disturbance are increasing while resources for natural resources management remain limited. Fully developing the capacity to operationalize the concept of ecological resilience can enable managers to prioritize the types and locations of management activities needed to optimize ecosystem conservation and restoration

Information and tools to conserve and restore Great Basin ecosystems

Keywords: Ecosystem health, Great Basin, Conservation of Natural Resource

Post-fire vegetation response at the woodland-shrubland interface is mediated by the pre-fire community

Understanding the drivers of ecosystem responses to disturbance is essential for management aimed at maintaining or restoring ecosystem processes and services, especially where invasive species respond strongly to disturbance. In this study, we used repeat vegetation surveys from a network of prescribed fire treatments at the woodland-shrubland interface in the Shoshone Mountains, Nevada, USA, to investigate post-fire responses of the understory plant community. First, we characterized post-fire community trajectories for sites located along an elevational gradient, hypothesizing a positive relationship between elevation and resistance to invasion. Unburned understory communities and their responses to disturbance differed along the gradient. As hypothesized, lower elevations experienced greater species turnover and higher invasive annual grass (Bromus tectorum) cover after fire. Second, we characterized post-fire plant community trajectories for sites with varying levels of pre-fire pinyon and juniper cover, hypothesizing that pre-fire tree dominance and associated reductions in perennial understory species lead to less predictable post-fire trajectories. Among sites with low-to-moderate tree cover, burning largely eliminated differences in understory composition, suggesting that biotic legacies were sufficient to result in predictable trajectories. In contrast, sites with high pre-fire tree cover transitioned into an annual forb-dominated community with sparse vegetation cover, suggesting that the loss of the understory community initiated unpredictable and divergent post-fire trajectories. Because plant communities were still changing four years after fire, it is unclear whether the alternate trajectories in sites with high tree cover will result in the formation of alternate states, or whether community composition will eventually converge with other sites at the same elevation. Results indicate that careful evaluation of site characteristics can be used to predict treatment outcomes at the woodland-shrubland interface, and to guide the appropriate use of prescribed fire or other management practices

Response of Conifer-Encroached Shrublands in the Great Basin to Prescribed Fire and Mechanical Treatments

In response to the recent expansion of piñon and juniper woodlands into sagebrush-steppe communities in the northern Great Basin region, numerous conifer-removal projects have been implemented, primarily to release understory vegetation at sites having a wide range of environmental conditions. Responses to these treatments have varied from successful restoration of native plant communities to complete conversion to nonnative invasive species. To evaluate the general response of understory vegetation to tree canopy removal in conifer-encroached shrublands, we set up a region-wide study that measured treatment-induced changes in understory cover and density. Eleven study sites located across four states in the Great Basin were established as statistical replicate blocks, each containing fire, mechanical, and control treatments. Different cover groups were measured prior to and during the first 3 yr following treatment. There was a general pattern of response across the wide range of site conditions. There was an immediate increase in bare ground and decrease in tall perennial grasses following the fire treatment, but both recovered by the second or third growing season after treatment. Tall perennial grass cover increased in the mechanical treatment in the second and third year, and in the fire treatment cover was higher than the control by year 3. Nonnative grass and forb cover did not increase in the fire and mechanical treatments in the first year but increased in the second and third years. Perennial forb cover increased in both the fire and mechanical treatments. The recovery of herbaceous cover groups was from increased growth of residual vegetation, not density. Sagebrush declined in the fire treatment, but seedling density increased in both treatments. Biological soil crust declined in the fire treatment, with no indications of recovery. Differences in plant response that occurred between mechanical and fire treatments should be considered when selecting management options

Developing a Model Framework for Predicting Effects of Woody Expansion and Fire on Ecosystem Carbon and Nitrogen in a Pinyon-Juniper Woodland

Sagebrush-steppe ecosystems are one of the most threatened ecosystems in North America due to woodland expansion, wildfire, and exotic annual grass invasion. Some scientists and policy makers have suggested that woodland expansion will lead to increased carbon (C) storage on the landscape. To assess this potential we used data collected from a Joint Fire Sciences Program demonstration area to develop a Microsoft Excel™ based biomass, carbon, and nitrogen (N) spreadsheet model. The model uses input for tree cover, soil chemistry, soil physical properties, and vegetation chemistry to estimate biomass, carbon, and nitrogen accumulation on the landscape with woodland expansion. The model also estimates C and N losses associated with prescribed burning. On our study plots we estimate in treeless sagebrush-steppe ecosystems, biomass accounts for 4.5 Mg ha−1 C and 0.3 Mg ha−1 N this is \u3c10% of total estimated ecosystem C and N to a soil depth of 53 cm, but as tree cover increases to near closed canopy conditions aboveground biomass may account for 62 Mg ha−1 C and 0.6 Mg ha−1 N which is nearly 53% of total estimated ecosystem C and 13% of total estimated ecosystem N to a soil depth of 53 cm. Prescribed burning removes aboveground biomass, C and N, but may increase soil C at areal tree cover below 26%. The model serves as a tool by which we are able to assess our understanding of the system and identify knowledge gaps which exist for this ecosystem. We believe that further work is necessary to quantify herbaceous biomass, root biomass, woody debris decomposition, and soil C and N with woodland expansion and prescribed fire. It will also be necessary to appropriately scale these estimates from the plot to the landscape

Plant Functional Groups and Species Contribute to Ecological Resilience a Decade After Woodland Expansion Treatments

Woody plant expansions are altering ecosystem structure and function, as well as fire regimes, around the globe. Tree-reduction treatments are widely implemented in expanding woodlands to reduce fuel loads, increase ecological resilience, and improve habitat, but few studies have measured treatment outcomes over long timescales or large geographic areas. The Sagebrush Treatment Evaluation Project (SageSTEP) evaluated the ecological effects of prescribed fire and cut-and-leave treatments in sagebrush communities experiencing tree expansion in North American cold desert shrublands. We used 10 yr of data from the SageSTEP network to test how treatments interacted with pre-treatment tree dominance, soil climate, and time since treatment to affect plant functional groups and dominant species. Non-sprouting shrub (Artemisia spp.), sprouting shrub, perennial graminoid, and annual grass responses depended on tree dominance and soil climate, and responses were related to the dominant species\u27 life-history traits. Sites with warm and dry soils showed increased perennial graminoid but reduced Artemisia shrub cover across the tree dominance gradient after prescribed burning, while sites with cool and moist soils showed favorable post-burn responses for both functional types, particularly at low to moderate tree dominance. Cut-and-leave treatments sustained or increased native perennial plant functional groups and experienced smaller increases in exotic annual plants in both soil climates across the tree dominance gradient. Both treatments reduced biocrust cover. Selecting appropriate tree-reduction treatments to achieve desired long-term outcomes requires consideration of dominant species, site environmental conditions, and the degree of woodland expansion. Careful selection of management treatments will reduce the likelihood of undesirable consequences to the ecosystem