The literature, long-term temporal data sets, and spatial data points surrounding livestock watering pints within rangeland communities wearer used to examine common assumptions and concepts used in models of vegetation dynamics. Of the stability concepts examined, the constancy concept was invalidated using long-term relict area data, whereas long-term data following disturbance indicated that sagebrush-dominated areas could be considered as resilient under circumstances examined. Pioshpere as well as relict and post-disturbance data indicated that the individualistic notion of vegetation change was favored. Species showing the most predictability (based on repeatability of abundance curves, and spatial and temporal serial correlations) were sagebrush and cheatgrass, specifically in their response to fire. Bunchgrasses were characterized by their persistence in abundance under all circumstances (grazing disturbance and fire disturbance) except long-term absence of fire. This, together with the support of the individualistic notion of plant community change, suggests examining change on a vital attributes basis with kinetic framework. It was found that most models of vegetation dynamics could be validated, because of the multivariate nature of the data examined. A closer examination of the requirements of range management for a models to be used as a basis for range condition and trend analysis determined that three basic model types are needed by range managers: First, a conceptual model for marrying divergent perspectives of different rangeland user groups; send, mechanistic models for the exploration of vegetation dynamics; and third, expert systems for information transfer. Further emphasis was placed on deriving a suitable conceptual models subscribing to the Objective of linking vegetation dynamics, range management, and monitoring within sagebrush-dominated areas. Important characteristics (derived from the data sets examined) included in this model are the recognition of static and dynamic plant communities, swathes of change rather than predefined pathways, the individualistic nature of change, and the recognition of spatial heterogeneity. Predictability at various scales was incorporated by focusing on cheatgrass and sagebrush, since these species indicated the most repeatable dynamics observed in the data sets, and were “common denominator”’ species (thus overcoming the problem of spatial heterogeneity). The undesired effects of cheatgrass and sage brush on other growth-forms suggest that monitoring and managing these undesired species may be a proactive way of managing for a desired plant community incorporating a balance of growth-forms.

The particular purpose of this study was to determine the effects of large-scale sagebrush reseeding projects on sage grouse populations and whether such effects were partly or entirely beneficial, neutral, or detrimental to the survival of such populations. During two seasons of field work, the studies initiated on a short-time basis had the following specific objectives: To compare the utilization by sage grouse of reseeded and non-reseeded lands for the seasonal activities of mating, nesting, raising a brood, fall coveying, and wintering. To compare the utilization by sage grouse of reseeded and non-reseeded lands for daily activities of feeding, watering, resting, hiding, and roosting. To determine fall and winter movements of the grouse in relation to reseeded lands. To determine the food and cover available to grouse on randomly selected sample plots To arrive at an index to food preferences through comparison of stomach analysis and food availability studies. To determine the effect of livestock grazing of reseeded lands on sage grouse. To determine the effect of plant succession on availability of food and cover within reseeded lands.

Wyoming big sagebrush (Artemisia tridentata Nutt.) is an important native shrub in the Great Basin because of its wide distribution where it dominates over 60 million ha and provides essential habitat and forage for many varied species. The hand collection of sagebrush seed often results in seed scarcity and the available seed quantities are at times inadequate to revegetate large areas that have been disturbed, resulting in a demand for sagebrush seed. Study locations were selected near Scipio and Sahara sand dunes of Utah, and treatments were 1-) control, no treatment applied area left undisturbed 2-) general chemical strip thinning 3-) general chemical thinning of entire stand, 4-) general mechanical strip thinning, and 5-) general mechanical thinning of the entire stand. Significant differences among treatments in seed yields were collected in 2011 at Scipio but not at Sahara. At Scipio, the mechanical strip of competing sagebrush in 3m strips was the most effective of all treatment and produced 2.47kg/ha compared to 4.624kg/ha in the control, but the mechanical land area was only utilizing half the compared control area. The chemical treatments produced 1.819kg/ha and 1.31kg/ha. The percent of sagebrush mortality by each treatment determined the level of competition killed in treatment areas. All treatments at both locations killed at least 57% of the sagebrush. Chemical treatments had a consistent kill rate at both locations, although lower than anticipated, but mechanical kill was the highest at 93% in Scipio. Both mechanical and chemical treated plots had increased cover levels of cheatgrass when compared to the control plots.

Galls of Artemisia tridentata Nutt. of Utah County were collected and described in detail. Of the ten galls collected, seven were caused by members of the Itonididae, two by members of the Trypetidae, and one by a member of the Curculionidae. Of the seven Itonid galls, six were caused by species of Diarthronomyia, and one by a species of Rhopalomyia. Two of the galls were caused by new species of Diarthronomyia. Three genera of the Scelionidae (Hymenoptera) and four genera of the Chalcidoidea (Hymenoptera) were also reared from the galls. A key to the ten galls was constructed, but does not necessarily include all the galls of big sagebrush of Utah County. To the writer's knowledce this is a first report of Eutreta diana O. S. (U. S. Geol. Sur. of Terr., 1877) in Utah. The position of the galls in their relationships as to complexity and specialization and possible origin has been pointed out.

Declining greater sage-grouse populations (Centrocercus urophasianus; hereafter sage-grouse) have led to increased concern regarding the long-term stability of the species. Previous research has identified factors contributing to the observed population declines. Habitat degradation and loss have been implicated as major factors in population declines. Although much is known about sage-grouse biology, more information is needed about population responses to specific management actions. This research was conducted to document sage-grouse responses to site-specific management actions. Additionally, I evaluated sage-grouse temporal and seasonal habitat-use and the comparability of techniques used by range and wildlife managers to measure vegetation responses of habitat management. Specifically, I evaluated 1) whether chemical analysis (gas chromatography) of sage-grouse fecal pellets could identify sagebrush species in sage-grouse winter diets, 2) the comparability of the line-point intercept and Daubenmire canopy cover methods for estimating canopy cover, 3) the response of sage-grouse broods to prescribed burns in a high elevation sagebrush community in northeastern Utah, and 4) the vegetation and insect characteristics of sites used by sage-grouse broods during a 24-hour period. I was able to determine wintering sage-grouse diets using gas chromatography by analyzing fecal pellets. This research also confirmed that black sagebrush (Artemisia nova) was an important component of sage-grouse winter diets in western Box Elder County and Parker Mountain populations. The line-point intercept and Daubenmire methods for estimating canopy cover are not comparable. Sage-grouse broods selected small (~ 25 ha) patchy prescribed burns in high elevation mountain big sagebrush (A. tridentata vaseyana) communities in northeastern Utah. Sage-grouse brood-site use in northwestern Utah did not differ during the diurnal hours, but nocturnal roost sites were characterized by shorter statured shrubs and more bare ground when compared to midday sites.

Since plants utilize CO��� as the substrate for photosynthesis, terrestrial plants may be directly affected by increasing levels of CO��� in the atmosphere. Plants native to the sagebrush steppe are predicted to increase in growth in response to elevated CO��� through increased water use efficiency and higher photosynthetic rates. This study examined the interactions between edaphic factors and CO��� in order to determine how species native to the sagebrush steppe may respond to elevated CO���. The objectives of these experiments were to: 1. determine if Sitanion hystrix, Artemisia tridentata ssp. wyomingensis, and Stipa thurberiana alter their growth and physiology in response to CO��� and soil temperature. 2. determine if Sitanion hystrix and Artemisia tridentata ssp. wyomingensis alter their growth and physiology in response to CO��� and water stress. Two experiments were conducted using environmentally controlled chambers. In the first experiment, Sitanion hystrix, Artemisia tridentata and Stipa thurberiana were exposed to ambient (374 ppm) or high (567 ppm) CO��� conditions and low (13��C) or high (18��C) soil temperature. After four months in the chambers, plants were harvested and plant material was divided into shoots, roots, and leaves. Results from the first experiment demonstrated that carbon dioxide and soil temperature modified the growth of these species. Sitanion hystrix increased its shoot and root weights at elevated CO��� when grown under low soil temperatures. Artemisia tridentata had lower plant weights under elevated CO��� and 18 ��C soil temperature than plants grown at ambient CO��� and 13��C. Shoots of Stipa thurberiana were responsive to soil temperature and roots were responsive to CO��� at 18��C. In the second experiment, Sitanion hystrix and Artemisia tridentata were exposed to ambient (371 ppm) or high (569 ppm) CO��� and well-watered or water stressed conditions. Results indicated that there were no interactive effects betweeen CO��� and water stress with respect to plant growth or physiology. CO��� increased water use efficiency in S. hystrix and increased water use efficiency of A. tridentata at the beginning of the experiment but had no interactive effects with water stress on growth or photosynthesis. Results suggested that the effect of CO��� on plant growth and productivity of the sagebrush steppe is dependent upon the soil temperature to which the plants are exposed. Differences between species in their response to CO���, soil temperature, and water stress were also apparent in this experiment. These controlled environment studies should pave the way for field studies in the sagebrush steppe in order to determine if differences in carbon allocation, resulting from changes in CO��� and soil temperature, are realized in the field. Alterations in carbon allocation may potentially alter the competitive relationships between species and influence successional processes in the sagebrush steppe. / Graduation date: 1997

Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 27-31). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 58-61). Also available on the World Wide Web.

Subalpine ecosystems are experiencing rapid changes in snow pack, temperature, and precipitation regime as a result of anthropogenic climate forcing. These changes in climate can have a profound effect on subalpine ecosystem structure and functioning, which may ultimately feed back to climate change. In this study, I examined the response of the subalpine meadow plant communities at the Rocky Mountain Biological Laboratory to natural and simulated climate change. First, I looked at whether changes in growing season precipitation or temperature regime would have the larger effect on subalpine ecosystem carbon flux. In a simulated warming experiment, changes in growing season precipitation had a tenfold larger effect on cumulative carbon flux than did the warming treatment. Along a natural climatic and elevational gradient, precipitation stimulates carbon uptake, particularly at higher elevations. Given projected decreases in summer precipitation in the high elevation Rockies, we predict a 20% decrease in carbon uptake from subalpine meadows. Second, I compared the taxonomic, phylogenetic and functional structure of plant communities along an elevational gradient to infer which climatic and biotic factors influence community assembly at each elevation. Floral and phenology traits become overdispersed at high elevation, mirroring phylogenetic relatedness, and suggesting pressure to diversify to attract pollinators during the abbreviated growing season. At the same time, leaf functional traits become clustered at high elevation, indicating multiple opposing assembly mechanisms in subalpine communities. Finally, I studied the natural history of sagebrush, Artemisia tridentate ssp. vaseyana, at its elevational range limit in subalpine meadows. In particular, I focused on the importance of warming and species interactions in elevational advance of the species. I found that facilitation by neighboring forbs was critical for sagebrush seedling survival, decreasing mortality by 75%. Seedling mortality was overwhelmingly due to desiccation of seedlings; therefore, neighboring forbs moderate temperature and water stress for seedlings. Despite the extremely limited growing season at high elevation caused by subfreezing temperatures, subalpine ecosystem structure and function are closely tied to water availability during the growing season. Therefore, improved predictions of future precipitation regimes over the Rocky Mountains will be our best tool for conservation of these fragile habitats.

The sagebrush (Artemisia spp.) steppe is undergoing rapid ecological change. The degradation of sagebrush steppe rangelands has resulted in the listing of more than 350 animals and plants as species of conservation concern. In addition, there has been a decrease in recreational values, reduced forage production, degraded water resources, and an increase in fire frequency. In the sagebrush steppe, success rates for seeding sagebrush after wildfire are notoriously low. Not only are sagebrush seeds hard to sow due to their small size and associated flower parts, but seedlings are exposed to numerous stresses that lowers their survivability. To improve sowing efficiency and reduce the associated stresses to seedling development we use seed enhancement technologies. In Chapter 1, we explain how a rotary seed coater can be used to agglomerate and apply enhancements to Wyoming big sagebrush (Artemisia tridentata spp. wyomingensis) seed. Using a mix of compost and clay we used a rotary seed coater to create small uniform agglomerates that allowed for enhancements to be applied to the seed. Our study demonstrated that agglomerates have no negative effects on seed germination and increased the overall flow of seed. In Chapter 2, we analyzed the addition of the plant hormone abscisic acid (ABA) in seed coatings. This hormone may delay seed germination and allow seedlings to avoid mortality due to over-winter freezing. We determined effects of different concentrations of ABA on total germination and timing of germination. Using a wet-thermal accumulation model, we estimated germination timing of seeds using soil temperature and water potential data for six different sites in the Great Basin. These models illustrate the variation in germination timing across the Great Basin. From our results we proposed the idea of using ABA to create a bet- hedging strategy in seed mixes to increase the probability that some seeds would germinate when conditions are favorable for seedling success.