Planting native species after a major disturbance is a critical tool land managers use to stabilize soils, restore ecosystem processes, and prevent weed invasion. However, within the sagebrush steppe and other arid and semi-arid environments the percentage of sown seeds that produce an adult plant is remarkably low. Applying fertilizers at the time of planting may improve native plant establishment by increasing the ability of the seedlings to cope with environmental stresses. However, traditional fertilizer applications are often economically infeasible and may be counterproductive by encouraging weed invasion. Seed coating technology allows for the efficient application of fertilizers within the microsite of the seeded species. The objective of our research was to determine the optimal rate of fertilizer to apply to the seed to improve seedling emergence and plant growth. We applied a phosphorus (P) rich fertilizer (0.13 g P g-1) to bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) Á. Löve) seeds in a rotary coater at rates ranging from 0 to 50 g of fertilizer 100 g-1 seed. Three separate studies were conducted to test germination, biomass, relative growth rate, and tissue nutrient uptake. Study one showed decreasing root and shoot biomass and increasing time to 50% germination as fertilizer rates increased. Study two showed no difference in relative growth rate between the controls and fertilizer treatments. Study three showed no difference in root and shoot biomass or nutrient concentration between treatments except in the lowest fertilizer treatment (10 g fertilizer 100 g-1 seed), which was significantly lower in root and shoot biomass than all other treatments but had higher P tissue concentrations than all other treatments. Collectively these results showed no evidence that a P fertilizer coating could aid in bluebunch wheatgrass seedling establishment. Because bluebunch wheatgrass and similar late-seral plants have evolved with low nutrient requirements they may not be physiologically capable of handling increased nutrient supply, which may explain the results of our studies. Continued studies and fieldwork need to be performed to evaluate the potential of fertilizer seed coatings in restoration efforts.

Identifying genetically appropriate plant materials for seed based restoration relies on the principle of local adaptation where the objective is to match adaptive genetic characteristics to variation in ecological clines pertinent to plant establishment and persistence. In this study, basin wildrye (Leymus cinereus (Scribn. & Merr.) Á. Löve) sources from 25 wild populations and 4 commercial varieties were planted at 4 test sites. We assessed initial establishment and short term persistance. Plantings failed at 2 sites in both 2013 and 2014, with too few plants to quantify differences. At the remaining 2 sites, local sources had higher initial establishment in just 1 of 10 comparisons. Among commercial sources, the cultivars Magnar and Trailhead initially outperformed local pooled materials at Fountain Green but not at Nephi. Initial establishment under row cover was dramatically better than uncovered controls at both sites, but only persisted for 4 years after planting at the Fountain Green site. The native forb study evaluated the effects of species, sowing depth and row cover on field emergence of 20 forbs. Overall, emergence was very low ranging between 0.2% and 1.0% for 16 of the 20 species. Four species exceeded 1% emergence. Depth effects were species, site and year dependent. The odds of emergence decreased with increasing depth for four species, increased for three species and were mixed between sites and years for the remaining species. The odds of emergence were better under row cover than for uncovered control plots. Depths evaluated were deeper than recommended for most species and likely hindered emergence for some species. Site and year had much more effect on observed emergence than depth or treatment. Developing simple diagnostics to identify subspecies is key in the restoration of sagebrush ecosystems. We evaluated the SoilWeb app as a tool to identify sagebrush in the field. We evaluated the accuracy of the Richardson et.al. (2015) technique to classify sagebrush stands and evaluated data modeling strategies to improve classification accuracy. We found the SoilWeb app to be an accurate and informative tool to identify native-wild sagebrush populations. The Richardson et.al. (2015) seed weight criteria correctly classified just 19% of our sample populations to the correct subspecies. To improve upon this, we evaluated multifactor modeling using recursive partitioning and classification trees. Our most accurate classification tree correctly classified 80% of 2x tridentata sites but just 45% of wyomingensis sites.

Understanding the relative importance of density-dependent and density-independent factors in driving population dynamics is one of the oldest challenges in ecology, and may play a critical role in predicting the effects of climate change on populations. We used long-term observational data to describe patterns in plant population regulation for 57 forb and grass species from three different ecosystems (arid desert grassland, semiarid sagebrush steppe, and subhumid mixed-grass prairie). Using a hierarchical partitioning approach, we (i) quantified the relative influence of conspecific density, heterospecific composition, and climate on temporal variation in population growth rates, and (ii) asked how the relative importance of these drivers depends on site aridity, species growth form and life expectancy, and abundance and spatial patterns. The data from one of the sites in this analysis are presented in one of the chapters of this thesis. We found that density-dependence had the strongest effect on species. Climate often had a significant effect, but its strength depended on growth form. Community composition rarely explained significant variation in growth rates. The relative importance of density, composition, and climate did not vary among sites, but was related to species' life histories: compared to forbs, grasses were more sensitive to climate drivers. Abundance and spatial clustering were negatively correlated with the importance of density dependence, suggesting that local rarity is a consequence of self-limitation. Our results show that interspecific interactions play a weaker role than intraspecific interactions and climate variability in regulating plant populations. Forecasting the impacts of climate change on populations may require understanding how changes in climate variables will affect the strength of density-dependence, especially for rare species.

The decline in greater sage-grouse (Centrocercus urophasianus; sage-grouse) populations across western North America has been primarily attributed to loss and fragmentation of their sagebrush (Artemisia spp.) habitats. This habitat loss is largely the result of increased human activities, with grazing by domestic livestock as the most predominant land use across the sagebrush ecosystem in North America. The goal of my research was to increase our understanding of the effects of livestock on sage-grouse populations. I reviewed the peer-reviewed literature for all published studies that reported potential effects of grazing on grouse species worldwide. I found that there was an overall negative effect of domestic livestock grazing on grouse populations in general. I compared sage-grouse nest success on two study sites managed under differing prescribed livestock grazing practices to determine their relative effects on sage-grouse nest survival. I found that nest survival was slightly higher in areas managed under high-intensity low-frequency rest-rotation practices. The difference was not statistically significant (P < 0.05). However, these areas received lower precipitation and were grazed at a higher stocking rate (AUM · ha-1) without negatively affecting nest survival compared to areas of that were mostly grazed as single pastures from May-September. Because livestock grazing in the sagebrush ecosystem has been historically facilitated with sagebrush reduction treatments to increase forage for livestock, I compared the relative effects of these treatments with the more direct effect from livestock grazing. Sagebrush treatments were found to have a greater effect on female sage-grouse survival than livestock grazing. This understanding can be useful for land managers looking to attenuate the effects of management decisions related to livestock grazing systems in the sagebrush ecosystem.

Management of greater sage-grouse (Centrocercus urophasianus) in the west has changed over the last several decades in response to environmental and anthropogenic causes. Many land and wildlife management agencies have begun manipulating sagebrush with herbicides, machinery, and fire. The intent of these manipulations (treatments) is to reduce sagebrush canopy cover and increase the density of grass and forb species, thus providing higher quality sage-grouse brood-rearing habitat. However, monitoring of sage-grouse response to such manipulations has often been lacking or non-existent. The objective of our study was to determine the response of sage-grouse to sagebrush reduction treatments that have occurred recently in Rich County, Utah. Our study areas were treated with a pasture aerator with the intent of creating sage-grouse brood-rearing habitat. We used pellet transects, occupancy sampling, and GPS radio telemetry to quantify sage-grouse habitat use in treated and untreated areas. Pellet transect, occupancy, and GPS radio telemetry methods all showed a strong pattern of sage-grouse use of treated sites during the breeding and early brood-rearing periods. Sage-grouse use of treated sites was greatest in lower elevation habitat (1950 to 2110 m), and use was highest during the breeding and early brood-rearing periods. We found very little use of higher elevation (2120 to 2250 m) treated or untreated sites. Our results suggest that sagebrush reduction treatments can have positive impacts on sage-grouse use at lower elevations and can be successful in creating brood-rearing habitat. Elevation differences and period of sage-grouse use were significant factors in our study in determining how beneficial sagebrush reduction treatments were for sage-grouse.

Forecasting the effects of climate change on plant and animal populations is a high priority in ecology. We studied the effects of climate on plant populations through the use of observational and experimental data, as well as analytical models. Our research questions were: (1) Do the effects of interannual climate variation on the population growth rates of widespread species show a coherent pattern across gradients of mean annual climate? (2) How well can population models fit to observational data predict the response of populations to field experiments that manipulate climate? And (3) does niche overlap between competitors predict the magnitude of competition-mediated indirect effects in mechanistic resource competition models? To test the first question, we assessed how interannual variation in climate affected the abundance of big sagebrush (Artemisia tridentata) at 131 monitoring sites across its range. We found that years of above average temperature increased sagebrush abundance at cold sites, but decreased sagebrush abundance at hot sites. This pattern indicates that sagebrush distribution may be limited by hot and cold temperatures at the extremes of its distribution. We addressed iv our second research question by fitting statistical models to over 25 years of observational data on the performance of four dominant plant species in a sagebrush steppe community. We then experimentally manipulated soil moisture in this community and tested how well the statistical models fit to observational data could predict species’ responses to the experimental treatments. In two out of four species, we found that including climate effects in our models helped us predict the population-level responses to the experiment. Moreover, effects of historical soil moisture variation on vital rates were generally consistent with the effects of drought and irrigation treatments. Our results provide some evidence that observational data can be used to predict species’ responses to climate change in the future. We addressed our third question by simulating environmental change in analytical models of resource competition and quantifying the size of direct and competition-mediated indirect effects that resulted. We showed that the magnitude of indirect effects increased as the niche overlap between competitors increased.

Sagebrush shrubsteppe ecosystems have increasingly garnered attention as an endangered ecosystem. Ninety nine percent of all sagebrush ecosystems are thought to have been impacted by humans, and over 50% of grassland and shrubsteppe species are believed to be in decline. Most of the research on sagebrush ecosystems has been conducted at lower elevations and in large expanses of sagebrush. A considerable amount of sagebrush is found at higher elevations, often in meadows found within a forest matrix. The role of this high-elevation habitat is poorly understood. We conducted bird, small mammal, vegetation, and soil surveys in sagebrush-dominated mountain meadows within the Wasatch-Cache National Forest in northeastern Utah. Meadows ranged from 0.6 to 782 hectares in size and included an impressive list of associated plant species. We detected two sagebrush-obligate species and numerous shrubsteppe-associated species. Each species appears to respond to different habitat characteristics, but all species that showed a significant relationship with meadow size were more likely to occur in larger meadows. Many species showed no relationship with size, suggesting that while larger meadows were preferred by some species, small meadows could also play an important role as habitat. While sagebrush-dominated mountain meadows were important for some species, we also failed to detect a number of species of interest. In particular, Sage Thrasher, Sage Sparrow, and pygmy rabbit were not found within the study area. North American Breeding Bird data suggests that Sage Thrashers can be found nearby. It is likely that these birds are only found in large expanses, and none of our meadows were large enough to support them. Sagebrush-dominated mountain meadows appear to be an important supplement to large expanses of sagebrush shrubsteppe habitat, but are not substitutable for all species.

Sagebrush plant communities are among the most threatened in North America. This project had two goals: to test how increased temperature affects native and nonnative forb species common to the Western sagebrush region and to evaluate land manager beliefs about changes in their ecosystems, including those affecting forb species. Native forbs Sphaeralcea munroana, Crepis acuminata, Linum lewisii, Penstemon palmeri, and Oenothera pallida and non-natives Erodium cicutarium and Lactuca serriola were each subjected to two treatments: experimental warming using open-top chambers and a control. Knowing how forbs used in restoration might respond to future conditions is both practical and economical information for land managers. Responses to an open-top chamber treatment suggest that S. munroana, L. lewisii, and P. palmeri may be resilient to predicted increases in temperature, while C. acuminata and O. pallida should be used with caution. As expected, temperature did not affect E. cicutarium fitness but did lead to earlier germination. This result supports the concept that competitive interactions between non-natives and natives could be compounded by increased temperature. Transplanted L. serriola was negatively affected by warming. Semi-structured phone interviews of range managers in Utah, Idaho, Nevada, Wyoming, Oregon, and Montana addressed demographics, local climate and land changes, and forb knowledge. Additionally, local long-term climate data sets were compared to responses. Most states respondents were evenly split about beliefs of climate change in their area (half said there were no changes, and have said they thought there were some changes). Montana was the exception; Montana’s recent increases in climate-related events may explain most of the managers noting changes. Managers that had more years at their job gave more qualified, but also more accurate climate answers. Managers saying there was no change tended to base their answers on recent weather conditions, while managers that said they did notice changes tended to base their answers on long-term patterns. Forbs typically were not viewed as an important indicator of ecosystem health or resilience. This study indicates restoration organizations might benefit from more specified outreach to managers which focuses on local climate, forbs (especially those known to be used by Greater sage-grouse), and solutions.

Restoration of Great Basin sagebrush communities is often attempted without understanding the potential impacts of either restoration treatments on the seed pool or the seed pool on restoration efforts. In addition, few studies have examined seed pools of the Great Basin and the role of vegetation in structuring seed pool communities. I evaluated soil seed pool dynamics of a Great Basin sagebrush community in a restoration context. In Chapter 1, I determined the relationship between the compositions of the seed pool and aboveground vegetation and the effect of shrubs (microhabitat effects) and perennial bunchgrass cover (community phase effects) on the seed pool community composition, seed density, and seed pool species richness. To evaluate the relationship between the two communities and the effects of microhabitat and community phase, the aboveground vegetation and the soil seed pools of different community phases and microhabitats were sampled prior to restoration. Similarity and distance metrics and non-metric multidimensional scaling (NMDS) were used to asses the relationship between the two communities. NMDS and analysis of variance (ANOVA) were used to determine the effects of aboveground community phase and microhabitat on the seed pool community. Results suggest that the relationship between the aboveground vegetation and seed pool community compositions varied according to the organizational level used for vegetation. In addition, microhabitat and community phase did influence seed density but not species richness. I sought to evaluate the effects of restoration treatments on the seed pool community in Chapter 3. To assess the impacts of restoration treatments, the seed pool community before and after treatments was censused. NMDS of the seed pool community and ANOVA on dominant species of the seed pool were performed to determine treatment effects. Results from this research suggest seed pool community composition and seed density varied temporally and spatially. Tebuthiuron and Plateau may have altered community composition whereas prescribed burn affected seed density. This research is applicable for land managers by helping determine the most effective restoration treatment, which will include effects on the seed pool.

Spraying with the chemical herbicide 2,4-D is the most widely used method of controlling big sagebrush. Spraying is very effective in increasing forage production and generally is not poisonous to either man or animals. Two procedures can be used to calculate the internal rate of return to big sagebrush control: standard and modified discounting. Standard discounting assumes all nonuse costs are incurred in the year of treatment, and the annual income stream is constant throughout the effective life of treatment. Modified discounting correctly assumes the nonuse cost is incurred in the period of deferment, and the income stream does not reach its full potential until after deferment. Thus, modified discounting yields a lower internal rate of return. Three big sagebrush control methods (spraying, burning, and chaining) offer internal rates of return which are greater than 8 percent (cost of obtaining capital for range improvement). The most important factors in determining the internal rate of return are the site vigor index and the amount of forage present before treatment. A larger pre-treatment forage yield will give a larger internal rate of return, assuming the vigor index is sufficiently high. If state and private rangelands infested with big sagebrush are not improved by spraying or other big sagebrush control methods, certain benefits, called opportunity costs, will be foregone. For spraying alone, the expected annual opportunity costs would be $3,048,102. The economic feasibility of controlling nearly 2 1/2 million acres of state and private rangelands infested with big sagebrush are excellent. The expected annual increase in carrying capacity of 1,830,000 acres of sagebrush rangeland meriting improvement by spraying is 765,855 AUMs. The remaining 623,000 acres meriting control other than by spraying could possibly increase the total number of additional AUMs to over 1 million.