Water is a limited and highly valued resource in the semi-arid Great Basin. Surface water sources are often small and widely spaced apart, comprising only 1-3% of the surface area of the overall landscape. Despite their small size, these springs and surrounding wet meadows have a substantial effect on the surrounding environment. Springs provide drinking water, forage and cover for livestock and wildlife, habitat for diversity of plant species and a resource for human-related activities. In recent years, many of these springs have become dewatered due to diversions of groundwater for municipal water and agriculture, and climatic shifts in precipitation affecting recharge. These hydrologic changes can cause a drop in the local water table that promotes a shift in the plant community from wetland-obligates to species that have more drought-tolerance. The root masses of the new plant community are insufficient to secure soils resulting in the erosion of the thalweg. This leads to channelization through the wet meadow, which drives the water table further underground. As degradation progresses, springs and wet meadows lose their ability to store water. The purpose of this thesis is to examine the responses of both the hydrologic and biologic factors to different springbox restoration techniques. Twenty-four spring sites were chosen in the Sheldon National Wildlife Refuge in northwestern Nevada. Each site was randomly assigned one of six different treatment designs. Variables for these studies included: surface soil moisture, soil moisture at varying depths, flow rates, water chemistry, plant community cover and frequency, biomass, wildlife visits and wildlife species numbers. We observed soil moisture increase over the majority of our sites, while flow rates only increased at the control sites. This may indicate that more water is being held in the soils around the spring source instead of being allowed to flow downstream. Biomass increased in four of our six treatments. All treatment types exhibited a similar effect on springs with none having a clearly more restorative effective than any others. This research suggests that springs in the Great Basin have unique characteristics and responses to restoration, and may need individualized approaches. Additionally, studies have shown that it may take many years for plant communities to recover after hydrologic restoration. Yearly variation caused by increased precipitation may be partially responsible for changes in hydrologic and biologic aspects of springs and wet meadows. Further data collection is needed to determine the true extent of treatment and yearly effects on spring restoration. In spite of the need for individualized approaches, restoration is possible. Simple solutions may be sufficient to recover hydrologic processes that maintain ecologic resilience.

No description available.

Studies of the hydrogeology of the southern Great Basin differ widely in their conclusions regarding the origin of major springs at Ash Meadows, in the Amargosa Desert, Nevada, and in the Furnace Creek- Nevares Spring area in Death Valley, California. The diversity of opinion reflects the following. First, ground water commonly moves between intermontane basins of the region via thick, highly fractured, and areally extensive Paleozoic carbonate rocks; the resulting lack of correspondence of topographic and ground-water divides precludes routine utilization of the water-budget method in the study of these basins. Second, subsurface hydraulic data for the regional carbonate aquifer are sparse and difficult to interpret because of the complex subsurface disposition of and hydraulic barriers within the aquifer. An analysis of hydrologic, geologic, geochemical, and isotopic data permits a first approximation of the subsurface watershed tributary to the cited spring groups. Water temperature, chemistry, isotope content, hydraulic head, and geologic relations indicate that the major springs at Ash Meadows and in the Furnace Creek-Nevares Spring area, though emerging from unconsolidated Quaternary strata, are fed by water moving directly from the underlying carbonate aquifer of Paleozoic age. Joint use of potentiometric, geologic, and isohyetal maps indicates that the subsurface watershed tributary to Ash Meadows is no smaller than 4,500 square miles. The Ash Meadows ground-water basin is bordered on the south and east by the Spring Mountains and Sheep Range, the principal recharge areas, and on the west by the Belted Range, Eleana Range, and Shoshone Mountain. A northern boundary was not definable, and some underflow from White River ground-water basin, 90 miles northeast of the springs, is probable. The hydrogeologic data do not support the conclusion of earlier studies that underflow from Pahrump Valley is the major source of the spring discharge at Ash Meadows; probably no more than a few percent of the total comes from that valley. Comparison of the size, climate, and discharge from the Ash Meadows basin with that of the surface watershed tributary to the Furnace Creek-Nevares Spring area indicates that most of the spring discharge in east-central Death Valley originates well beyond its confines. Disposition of the carbonate aquifer favors the movement of ground water into Death Valley from central Amargosa Desert. Water in the carbonate aquifer in the latter area may be derived from the Ash Meadows basin, from the overlying valley fill, or both. Five hydrochemical facies were distinguished by percentage of major cations and anions in ground water from 147 sources. The hydrochemical facies reflect both the mineralogy of strata within recharge areas and downward crossflow from a Tertiary tuff aquitard into the carbonate aquifer. The areal distribution of these facies provides evidence for a northeasterly source of the Ash Meadows discharge, absence of significant underflow from Pahrump Valley to Ash Meadows, and movement of water from the central Amargosa Desert to the Furnace Creek- Nevares Spring area. The data are also compatible with southwestward underflow into the Ash Meadows basin from the White River basin. The deuterium content of 53 water samples from 27 major valleylevel springs and selected wells falls into several areally distinct patterns which suggest that 35 percent of the Ash Meadows discharge is derived from the White River basin, that underflow from Pahrump Valley is unlikely, and that water discharging in the Furnace Creek-Nevares Spring area may be related to water in the carbonate aquifer within the Ash Meadows basin. However, other interpretations are possible indicating that unequivocal interpretations about the regional flow system cannot be made from isotopic data alone.

Crested wheatgrass (Agropyron cristatum [L.] Gaertn.) is one of the most commonly seeded grass species in the western United States and dominates thousands of hectares in the Great Basin. Although many degraded Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) plant communities have been seeded with crested wheatgrass, successional pathways, influence of soil attributes, and cultivation history on the vegetation of these communities have not been fully characterized. I sought to identify community phases, vegetative differences, and soil attributes that explain variation among 35 Wyoming big sagebrush communities historically seeded with crested wheatgrass. All communities were more than 30 years old and had not experienced fire, or received subsequent chemical or mechanical treatments following their original seeding. Species richness, diversity, vegetation cover, and soil samples were measured in four 20 x 5 m intensive Modified Whittaker plots per community. Hierarchical clustering and principal component analysis of three indicator species (crested wheatgrass, Sandberg bluegrass, and Wyoming big sagebrush) identified four distinct community phases. Community phase 1 was dominated by crested wheatgrass and had the lowest species richness and cover of big sagebrush. Phases 2 and 3 had the highest species richness and cover of native species. Phase 4 was dominated by big sagebrush and had the lowest cover of crested wheatgrass. Community phases differed significantly for soil texture, soil nitrogen, and ground cover characteristics. Bare soil was almost double on loam-textured soils and rock cover was higher on clay loam texture soils (P < 0.05) as well as native plant cover. Communities previously cropped occurred on more coarse-textured soils and had 6-fold lower native species cover and double exotic herbaceous and crested wheatgrass cover. Cropping occurred on favorable, low rock, fine-texture soils, the same soils that favor crested wheatgrass production and reduce resilience of native plant composition. Delineation of community phases provided a new, empirically based state-and-transition model, while the characterization of soil attributes and disturbance history provided information about feedback mechanisms influencing dominant species that delineate community phases and effect community structure. This information can be used to assist in the development of management strategies in crested wheatgrass seeded communities.

The range of a species often extends across a diverse landscape, necessitating that individuals make different movement and habitat decisions, despite consistent food and shelter requirements. Great Basin gophersnakes (Pituophis catenifer deserticola) are threatened in Canada, where they occur at the northern extent of their range in southern interior river valleys of British Columbia such as the Okanagan Valley. I followed 39 radio-transmittered adult gophersnakes at four sites in the Okanagan, to obtain information on life history, movement and range patterns, and habitat use. Habitat selection and movement patterns exhibited by gophersnakes differed between study sites, sexes, and months, indicating that snake choice varies depending on resources and life history traits. Despite these fine-grain differences, males moved more than females in the spring. In addition to this, females moved more than males in the summer and fall. Differences in movement and range were apparent among the study sites. Habitat selection differed by study site, however rock-outcrops were consistently selected overall. Microhabitat selection varied, but retreat sites including logs, rocks, and holes in the ground, were consistently located closer than random. Hibernation sites in the south Okanagan were in rock features, while in the north Okanagan a good proportion were in rodent burrows in hillsides. Hibernation site fidelity was low, and annual reproduction was common. Oviposition sites were on south-facing slopes of moderate grade with little to moderate grass cover. Three ecdysis periods were observed when most or all transmitter-equipped snakes shed their skin. These findings will be very valuable to species conservation goals in British Columbia when developing guidelines on the habitats and sizes of areas to protect. With an iii understanding of the movement and ranges patterns exhibited by individuals, the area required to sustain a healthy population of gophersnakes can be determined. Knowledge of the habitats and microhabitats gophersnakes select makes it possible to identify and protect important areas at sites known to contain gophersnakes, including the Vaseux, Ripley, and Vernon study sites. Characterization of hibernation and oviposition sites allows surveys to identify these areas in locations that may support gophersnakes. Finally, identification of the timing of various important life history behaviours means human disturbance can be avoided during mating and oviposition periods, especially on sites such as Vernon, where land is used for multiple purposes.

Digital soil mapping (DSM) relies on quantitative relationships between easily measured environmental covariates and field and laboratory data. We applied innovative sampling and inference techniques to predict the distribution of soil attributes, taxonomic classes, and dominant vegetation across a 30,000-ha complex Great Basin landscape in southwestern Utah. This arid rangeland was characterized by rugged topography, diverse vegetation, and intricate geology. Environmental covariates calculated from digital elevation models (DEM) and spectral satellite data were used to represent factors controlling soil development and distribution. We investigated optimal sample size and sampled the environmental covariates using conditioned Latin Hypercube Sampling (cLHS). We demonstrated that cLHS, a type of stratified random sampling, closely approximated the full range of variability of environmental covariates in feature and geographic space with small sample sizes. Site and soil data were collected at 300 locations identified by cLHS. Random forests was used to generate spatial predictions and associated probabilities of site and soil characteristics. Balanced random forests and balanced and weighted random forests were investigated for their use in producing an overall soil map. Overall and class errors (referred to as out-of-bag [OOB] error) were within acceptable levels. Quantitative covariate importance was useful in determining what factors were important for soil distribution. Random forest spatial predictions were evaluated based on the conceptual framework developed during field sampling.

The range of a species often extends across a diverse landscape, necessitating that individuals make different movement and habitat decisions, despite consistent food and shelter requirements. Great Basin gophersnakes (Pituophis catenifer deserticola) are threatened in Canada, where they occur at the northern extent of their range in southern interior river valleys of British Columbia such as the Okanagan Valley. I followed 39 radio-transmittered adult gophersnakes at four sites in the Okanagan, to obtain information on life history, movement and range patterns, and habitat use. Habitat selection and movement patterns exhibited by gophersnakes differed between study sites, sexes, and months, indicating that snake choice varies depending on resources and life history traits. Despite these fine-grain differences, males moved more than females in the spring. In addition to this, females moved more than males in the summer and fall. Differences in movement and range were apparent among the study sites. Habitat selection differed by study site, however rock-outcrops were consistently selected overall. Microhabitat selection varied, but retreat sites including logs, rocks, and holes in the ground, were consistently located closer than random. Hibernation sites in the south Okanagan were in rock features, while in the north Okanagan a good proportion were in rodent burrows in hillsides. Hibernation site fidelity was low, and annual reproduction was common. Oviposition sites were on south-facing slopes of moderate grade with little to moderate grass cover. Three ecdysis periods were observed when most or all transmitter-equipped snakes shed their skin. These findings will be very valuable to species conservation goals in British Columbia when developing guidelines on the habitats and sizes of areas to protect. With an iii understanding of the movement and ranges patterns exhibited by individuals, the area required to sustain a healthy population of gophersnakes can be determined. Knowledge of the habitats and microhabitats gophersnakes select makes it possible to identify and protect important areas at sites known to contain gophersnakes, including the Vaseux, Ripley, and Vernon study sites. Characterization of hibernation and oviposition sites allows surveys to identify these areas in locations that may support gophersnakes. Finally, identification of the timing of various important life history behaviours means human disturbance can be avoided during mating and oviposition periods, especially on sites such as Vernon, where land is used for multiple purposes.

The range of a species often extends across a diverse landscape, necessitating that individuals make different movement and habitat decisions, despite consistent food and shelter requirements. Great Basin gophersnakes (Pituophis catenifer deserticola) are threatened in Canada, where they occur at the northern extent of their range in southern interior river valleys of British Columbia such as the Okanagan Valley. I followed 39 radio-transmittered adult gophersnakes at four sites in the Okanagan, to obtain information on life history, movement and range patterns, and habitat use. Habitat selection and movement patterns exhibited by gophersnakes differed between study sites, sexes, and months, indicating that snake choice varies depending on resources and life history traits. Despite these fine-grain differences, males moved more than females in the spring. In addition to this, females moved more than males in the summer and fall. Differences in movement and range were apparent among the study sites. Habitat selection differed by study site, however rock-outcrops were consistently selected overall. Microhabitat selection varied, but retreat sites including logs, rocks, and holes in the ground, were consistently located closer than random. Hibernation sites in the south Okanagan were in rock features, while in the north Okanagan a good proportion were in rodent burrows in hillsides. Hibernation site fidelity was low, and annual reproduction was common. Oviposition sites were on south-facing slopes of moderate grade with little to moderate grass cover. Three ecdysis periods were observed when most or all transmitter-equipped snakes shed their skin. These findings will be very valuable to species conservation goals in British Columbia when developing guidelines on the habitats and sizes of areas to protect. With an iii understanding of the movement and ranges patterns exhibited by individuals, the area required to sustain a healthy population of gophersnakes can be determined. Knowledge of the habitats and microhabitats gophersnakes select makes it possible to identify and protect important areas at sites known to contain gophersnakes, including the Vaseux, Ripley, and Vernon study sites. Characterization of hibernation and oviposition sites allows surveys to identify these areas in locations that may support gophersnakes. Finally, identification of the timing of various important life history behaviours means human disturbance can be avoided during mating and oviposition periods, especially on sites such as Vernon, where land is used for multiple purposes. / Irving K. Barber School of Arts and Sciences (Okanagan) / Biology, Department of (Okanagan) / Graduate

Little information is available on the extent of local adaptation for many native grass species. This is the case for squirreltail (Elymus section Sitanion), despite this group's prevalence and importance in rangeland restoration efforts. I evaluated 32 populations of E. elymoides ssp. brevifolius race C, a phylogenetic subdivision of bottlebrush squirreltail (E. elymoides) centered in the northern Intermountain West, for phenotypic variables and neutral genetic markers to measure their association with geographical origin. Phenotypic traits were measured in common field and greenhouse environments, and genetic diversity was assessed using Amplified Fragment Length Polymorphism. Three factors were extracted from the phenotypic data set using common factor analysis. Factor 1 explained 37.7% of the variation among all of the variables; it had positive factor loadings for phenology (late maturity), biomass, and leaf area index, negative loadings for leaf area and root length, and was negatively correlated with elevation (r = -0.71). Factor 2 explained 14.5% of the variation among all of the variables; it had positive factor loadings for plant height and leaf number per tiller, negative loadings for seed yield and tiller number, and was positively correlated with longitude (r = 0.54) and average annual minimum temperature (r = 0.39). Factor 3 explained 12.8% of the variation among all of the variables; it had highly positive factor loadings for specific root length and specific leaf area, negative loadings for canopy height and mass per tiller. Correlations among phenotypic, environmental, genotypic, and geographic-origin distances were positive (r = 0.723-0.900), which suggests that ecotypic variation is an important feature of this group. This information, in conjunction with previously established Level III ecoregions, was used to delineate four adaptive zones for race C.

Heterogeneous spatial and temporal distributions of soil resources important to plant growth have been documented in the sagebrush steppe ecosystem. There can exist as much variability in soil resources within the root zone of individual plants as exists across an entire field. The objective of this dissertation research was to evaluate how plants respond to, utilize and influence the spatial heterogeneity of soil resources. The three specific sets of questions addressed are outlined in the three main chapters of this dissertation. My first study addressed how the number and concentration of phosphorus (P) patches in the root zone of an individual Artemisiaplant influenced the ability of the plant to increase root P uptake capacity from the enriched patches as compared to roots from unenriched soil. I found that root uptake kinetics in the most enriched patches in general was not limited by the number or concentration of phosphorus patches experienced by the plant. However, the plants could modulate the quantity of P acquired from a target patch as the number of patches experienced increased. My second study addressed how six species common to the Great Basin, which represent three different growth forms, utilized nitrogen (N) from patches or a uniform distribution. The two species within the two perennial growth forms, shrub and tussock grass, revealed different capacities for acquiring N from concentrated patches immediately adjacent to a plant and from N applications at a distance from plants. This suggests the potential for different root foraging behavior. The two annual species used concentrated N patches more effectively than uniform applications. My third study described decimeter scale variability of soil water potential (Ψs) in the interspace of two perennial plants at different time scales and at different soil moisture conditions. The mean Ψs was more spatially consistent in the interspace between plants during a midsummer dry period compared to an early summer period. Diel Ψs fluctuations during an early summer dry period was more spatially consistent than a midsummer dry period. When soil moisture was recharged by precipitation there were no spatial diel patterns and the mean Ψs was autocorrelated across the area evaluated.