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Author: Martha M. Brabec Publisher: ISBN: Category : Big sagebrush Languages : en Pages : 116
Book Description
"The loss of big sagebrush (Artemisia tridentata) throughout the Great Basin Desert has motivated efforts to restore it because of fire and other disturbance effects on sagebrush-dependent wildlife and ecosystem function. Initial establishment is the first challenge to restoration, and appropriateness of seeds, climate, and weather variability are factors that may explain success or difficulties in big sagebrush restoration efforts. This project provided several ways of assessing climate responses of big sagebrush seedlings during the critical establishment phase post-fire. We evaluated eleven different seed sources of big sagebrush from all three subspecies, dissimilar climates-of-origin, and different ploidy levels to assess how subspecies, cytotype, and climate-of-origin affect initial establishment of sagebrush in a common garden study. We assessed ecophysiological-climate adaptation as it relates to seedling performance using a suite of dependent variables, including: survival, growth, water balance, photosynthesis, and threshold freezing responses. Results indicate the importance of minimum temperatures to seedling establishment, and reveal a gradient of physiological responses to freezing that inform big sagebrush adaptation and functional diversity. We then used in-situ experimental warming to isolate minimum temperatures, and test the effects of warming on seedling physiological performance for the three dominant subspecies of big sagebrush: A.t. tridentata, A.t. vaseyana, and A.t. wyomingensis. Experimental warming further supported our minimum temperature hypothesis, indicating that warming may alter seedling freezing response thereby affect growth and survival. In a third experiment, we evaluated how initial establishment of big sagebrush is influenced by management treatments on the herb layer, as post-fire rehabilitation frequently involves alterations of the plant community and soil. Results suggest that drill seeding combined with land management treatments that cause disturbance of the herb layer and soil surface may negatively affect sagebrush during the establishment phase. Also, seedlings from local seed or faster-growing populations had greater survival than seedlings from climates that differed from the experimental site. In summary, we provide experimental evidence for the importance of minimum temperatures and seed sources to big sagebrush ecology and management of sagebrush systems. As the climate warms, selection for population-specific freezing resistance mechanisms may alter subspecies distributions. Our data indicated that warming could increase relative abundance of A.t. tridentata compared to A.t. wyomingensis at our Birds of Prey National Conservation Areas study site on the lower Snake River plain. The underlying mechanism for this is greater stress overcome by changes in resource allocation from freezing protection to growth, as well as an extraction of deeper soil water resources in A.t. tridentata. Mortality of A.t. vaseyana appeared to relate to drought stress and greater vulnerability to minimum temperature exposure. Understanding differences in big sagebrush populations' ability to compete with different types and abundances of herbs as well as variation in freezing resistance mechanisms will contribute to appropriate seed selection for particular restoration sites. The implication is that selection of seed is critical for big sagebrush restoration success.."--Boise State University ScholarWorks.
Author: Martha M. Brabec Publisher: ISBN: Category : Big sagebrush Languages : en Pages : 116
Book Description
"The loss of big sagebrush (Artemisia tridentata) throughout the Great Basin Desert has motivated efforts to restore it because of fire and other disturbance effects on sagebrush-dependent wildlife and ecosystem function. Initial establishment is the first challenge to restoration, and appropriateness of seeds, climate, and weather variability are factors that may explain success or difficulties in big sagebrush restoration efforts. This project provided several ways of assessing climate responses of big sagebrush seedlings during the critical establishment phase post-fire. We evaluated eleven different seed sources of big sagebrush from all three subspecies, dissimilar climates-of-origin, and different ploidy levels to assess how subspecies, cytotype, and climate-of-origin affect initial establishment of sagebrush in a common garden study. We assessed ecophysiological-climate adaptation as it relates to seedling performance using a suite of dependent variables, including: survival, growth, water balance, photosynthesis, and threshold freezing responses. Results indicate the importance of minimum temperatures to seedling establishment, and reveal a gradient of physiological responses to freezing that inform big sagebrush adaptation and functional diversity. We then used in-situ experimental warming to isolate minimum temperatures, and test the effects of warming on seedling physiological performance for the three dominant subspecies of big sagebrush: A.t. tridentata, A.t. vaseyana, and A.t. wyomingensis. Experimental warming further supported our minimum temperature hypothesis, indicating that warming may alter seedling freezing response thereby affect growth and survival. In a third experiment, we evaluated how initial establishment of big sagebrush is influenced by management treatments on the herb layer, as post-fire rehabilitation frequently involves alterations of the plant community and soil. Results suggest that drill seeding combined with land management treatments that cause disturbance of the herb layer and soil surface may negatively affect sagebrush during the establishment phase. Also, seedlings from local seed or faster-growing populations had greater survival than seedlings from climates that differed from the experimental site. In summary, we provide experimental evidence for the importance of minimum temperatures and seed sources to big sagebrush ecology and management of sagebrush systems. As the climate warms, selection for population-specific freezing resistance mechanisms may alter subspecies distributions. Our data indicated that warming could increase relative abundance of A.t. tridentata compared to A.t. wyomingensis at our Birds of Prey National Conservation Areas study site on the lower Snake River plain. The underlying mechanism for this is greater stress overcome by changes in resource allocation from freezing protection to growth, as well as an extraction of deeper soil water resources in A.t. tridentata. Mortality of A.t. vaseyana appeared to relate to drought stress and greater vulnerability to minimum temperature exposure. Understanding differences in big sagebrush populations' ability to compete with different types and abundances of herbs as well as variation in freezing resistance mechanisms will contribute to appropriate seed selection for particular restoration sites. The implication is that selection of seed is critical for big sagebrush restoration success.."--Boise State University ScholarWorks.
Author: Kyle A. Taylor Publisher: ISBN: 9781339440484 Category : Big sagebrush Languages : en Pages :
Book Description
Big sagebrush (Artemisia tridentata) ecosystems have experienced loss over large portions of their historic range throughout the intermountain western United States over the last two centuries. Leading into the 21st century, much of this loss could be attributed to anthropogenic land conversion -- particularly from regional population growth, agricultural development, and the spread of invasive species. Over the course of the 21st century, climate change and invasive grassland conversion (Bromus tectorum) are expected to further alter the structure of regional sagebrush ecosystems, potentially contributing to range loss for big sagebrush and its many obligate species. My overall objective was to investigate the exposure of sagebrush ecosystems to risks from climate change and invasive species spread. I developed a series of species distribution models (SDMs) for three major sagebrush subspecies and compare the trajectory of regional sagebrush ecosystems under future climate conditions. I assessed my confidence in range projections for big sagebrush under future climate conditions using a sensitivity analysis to explore deficiencies in the underlying data behind my SDMs. Lastly, I attempted to assess the invasibility of climatically-stable sagebrush ecosystems by developing and deploying a process-based demographic model for cheatgrass at sites throughout the intermountain region. I implemented a series of big sagebrush species distribution models (SDMs) fit to individual subspecies records of big sagebrush. I used climate variables previously described as limiting for big sagebrush as explanatory data and extrapolate the models into mid-century and end-of-century conditions using an ensemble of recent global circulation model (GCM) data. I expected all three big sagebrush subspecies to respond negatively to increases in temperature and drier summer conditions forecasted for much of the intermountain region, assuming that future environmental conditions would warm beyond the environmental tolerances to which big sagebrush is physiologically adapted to. However, at the subspecies level, this did not appear to be the case. Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) and basin big sagebrush (Artemisia tridentata ssp. tridentata) both demonstrated slight range expansion, largely along elevational gradients, under end-of-century forecasts across GCMs. Although experiencing loss within southern portions of their current range, the warmer winter conditions and slightly drier summer conditions forecasted for wyomingensis and tridentata are not so unusual that the subspecies don’t currently encounter these conditions within portions of their current range. Notably, mountain big sagebrush (Artemisia tridentata ssp. vaseyana) does respond negatively to future climate conditions, with winter temperatures increasing beyond what the subspecies experiences across its current range. Unlike ssp. tridentata and wyomingensis, vaseyana does not appear to have a large elevational gradient to retreat into under future climate conditions, which could result in potentially large losses of its current range if the subspecies is unable to adapt and compete under warmer conditions. In order to better indicate confidence in SDM predictions for big sagebrush, I used a Monte Carlo-based sensitivity analysis to demonstrate how uncertainties attributed to occurrence, absence, and climate data biases propagate through two commonly used SDM algorithms (Generalized Linear Models [GLMs] and Random Forests [RF]) for sagebrush ecosystems dominated by ssp. wyomingensis and tridentata. I derived predictive intervals for both GLM and RF and used the intervals to produce envelopes indicating areas of high and low predictive confidence in SDM predictions and explore how bias can contribute to latitudinal and elevational drift in suitability predictions. Both algorithms demonstrated sensitivities to climate and presence-record uncertainty that translated to large geographic uncertainty in predictions. I found that RF is more sensitive to bias than GLM, and that climate and presence record bias contributed to greater predictive ambiguity than absence record uncertainty. I found that uncertainties in predictions arising from data uncertainty could easily produce the same magnitude of range shift as those observed under mid-century (2050) predictions of distributional change for big sagebrush under climate change, suggesting that mid-century forecasts of change for big sagebrush are not so unusual that they couldn’t also be explained by biases affecting underlying data. However, many late-century (2100) predictions of suitability change appear to diverge from what was observed in our sensitivity analysis and deserve greater confidence. As roughly half of climatically suitable space available to big sagebrush throughout the intermountain region has experienced some degree of invasion by cheatgrass, it’s continued spread is an important factor to consider in assessing the long-term viability of big sagebrush ecosystems. Using a soil hydrology model (SOILWAT) and a meta-analysis conducted from a number of studies of cheatgrass’ demography and physiology, I built a process-based model that simulates cheatgrass population growth over time. I applied the model to current climate conditions at a number of sites sampled from sagebrush ecosystem subspecies strata across the intermountain region and found detectable differences in population suitability response. The cheatgrass demographic model demonstrates detectable differences in population response between montane sites (suitable for ssp. vaseyana) and basin sites (suitable for ssp. wyomingensis and tridentata) that suggest basin subspecies ranges are more suitable for cheatgrass than montane sites. I also demonstrate that basin subspecies are typically closer to known invasive annual grasslands throughout the intermountain region, and are probably more susceptible to cheatgrass propagule pressure. A synthesis of results across my studies suggests differing fates for regional sagebrush ecosystems. Although ssp. wyomingensis and tridentata dominated sagebrush ecosystems may be potentially robust to future climate change, they demonstrate a greater risk to cheatgrass invasion, which could challenge the long-term stability of sagebrush ecosystems in the basin interior of the intermountain region. Conversely, although montane sagebrush ecosystems dominated by ssp. vaseyana may be at comparatively less risk of cheatgrass invasion, these sagebrush ecosystems will face greater exposure to climate change stressors over the course of the 21st century.
Author: Bruce Leigh Welch Publisher: ISBN: Category : Big sagebrush Languages : en Pages : 38
Book Description
This paper examines the scientific merits of eight axioms of range or vegetative management pertaining to big sagebrush. These axioms are: (1) Wyoming big sagebrush (Artemisia tridentata ssp.wyomingensis) does not naturally exceed 10 percent canopy cover and mountain big sagebrush (A.t.ssp.vaseyana) does not naturally exceed 20 percent canopy cover; (2) As big sagebrush canopy cover increases over 12 to15 percent, bare ground increases and perennial grass cover decreases; (3) Removing, controlling, or killing big sagebrush will results in a two or three or more fold increase in perennial grass production; (4) Nothing eats it; (5) Biodiversity increases with removing, controlling, thinning, or killing of big sagebrush; (6) Mountain big sagebrush evolved in an environment with a mean fire interval of 20 to 30 years; (7) Big sagebrush is an agent of allelopathy; and (8) Big sagebrush is a highly competitive, dominating, suppressive plant species.
Author: Bruce Leigh Welch Publisher: ISBN: Category : Big sagebrush Languages : en Pages : 220
Book Description
Pioneers traveling along the Oregon Trail from western Nebraska, through Wyoming and southern Idaho and into eastern Oregon, referred to their travel as an 800 mile journey through a sea of sagebrush, mainly big sagebrush ( Artemisia tridentata). Today approximately 50 percent of the sagebrush sea has given way to agriculture, cities and towns, and other human developments. What remains is further fragmented by range management practices, creeping expansion of woodlands, alien weed species, and the historic view that big sagebrush is a worthless plant. Two ideas are promoted in this report: (1) big sagebrush is a nursing mother to a host of organisms that range from microscopic fungi to large mammals, and (2) many range management practices applied to big sagebrush ecosystems are not science based.
Author: Andrii Zaiats Publisher: ISBN: Category : Big sagebrush Languages : en Pages : 75
Book Description
"Post-fire restoration of degraded sagebrush ecosystems over large areas of the Great Basin is challenging, in part due to unpredictable outcomes. Low rates of restoration success are attributed to increasing frequencies of wildfires, biological invasions, and climate variability. Quantifying restoration outcomes by accounting for sources of biotic and abiotic variability will improve restoration as a predictive science. One source of biotic variability is neighbor interactions, which can regulate demographic parameters of coexisting species and are an important determinant of community structure, ecosystem functions, and population dynamics. Our objective was to quantify how intraspecific variability in big sagebrush, Artemisia tridentata, including three subspecies and two ploidy levels, is related to subspecies' reaction to conspecific neighbor presence. Neighbor interactions can alter population growth rate via competition or facilitation depending on specific environmental conditions. Using a long-term common garden experiment, we developed spatially-explicit hierarchical models to quantify the effects of size-structured crowding on plant growth and survival. We found that neighbor interactions can vary significantly over time and space, and tend to be more pronounced under wetter and cooler climate conditions. We further tested if water availability, one of the major limiting factors in arid ecosystems, can underlie competitive interactions in a common garden, including density dependence. We used a deuterium-tracer experiment to quantify belowground zone of influence and crowding effect on plant water uptake. The results suggest that intraspecific variability in lateral root extent may be linked to subspecies identity and ploidy level. We did not find strong evidence that neighbor presence and size can alter water uptake from a shallow soil horizon, potentially suggesting size-independent partitioning of water resources between neighboring plants. We further hypothesize that variability in root architecture may reflect an axis for ecohydrological niche segregation contributing to the process of plant coexistence and evolution in heterogeneous landscapes. Our study complements previous knowledge of belowground processes in big sagebrush populations, including patterns of resource acquisition, and indicates promising avenues for further research of the ecology and evolution of this species. The results highlight how local plant-plant interactions can be a source of variation in common garden experiments, which are used to evaluate adaptive capacity and seed transfer zone development for A. tridentata populations. Potential applications of our work include planting density recommendations for big sagebrush in applied and experimental contexts, and provide mechanistic understanding of intraspecific diversification and ecological tradeoffs related to local adaptations."--Boise State University ScholarWorks.
Author: Trace E. Martyn Publisher: ISBN: 9781339151410 Category : Big sagebrush Languages : en Pages : 94
Book Description
Big sagebrush (Artemisia tridentata) is endemic to semiarid western North America. Big sagebrush plant communities are important for recreating and grazing but are also essential habitat for many plant and animal species including the greater sage-grouse ( Centrocercus urophasianus). Recent predictions suggest that climatic suitability for big sagebrush under future climate change will increase along the northeastern edge of the existing big sagebrush distribution or the predicted leading edge. The main objective of my research was to characterize big sagebrush plant communities adjacent to the leading edge of the distribution using both field and modeling studies. I used a field study to characterize the established plant community and the seed bank in plant communities adjacent to the leading edge. I quantified the plant community composition, soil texture, and cover as well as the seed bank for 3 sites in northeastern Montana, USA. I also used a paired soil water and individual plant model (STEPWAT) to assess big sagebrush plant community response to climate change. I ran simulations under current and future climate conditions for mid and late-century predictions using 10 Global Circulation Models (GCMs) for 10 sites adjacent to the predicted leading edge of the big sagebrush distribution. In big sagebrush plant communities adjacent to the leading edge, there was less than 30% similarity in the relative abundance of species between the established plant community and the seed bank. This difference was primarily driven by an overrepresentation of annual forbs and an underrepresentation of big sagebrush in the seed bank compared to the established plant community. Simulations of big sagebrush plant communities adjacent to the leading edge showed no substantial change in plant community functional type composition under future climate for mid and late-century time periods. Sagebrush and total biomass decreased in the future but, depending on the scenario and GCM, there was a wide range of potential biomass values for all functional groups varying in direction of change and amplitude. These results support future predictions of no change in climatic suitability for big sagebrush plant communities adjacent to the leading edge. Current big sagebrush plant communities adjacent to the leading edge appear to be able to respond well to climate change. These communities could support big sagebrush range expansion into the leading edge given the availability of seeds. My work will help inform the management of these communities under future climate change.
Author: Martha M. Brabec
Author: Martha M. Brabec
Author: Kyle A. Taylor
Author: Bruce Leigh Welch
Author: Bruce Leigh Welch
Author: Andrii Zaiats
Author: James Russell Johnson
Author: Trace E. Martyn
Author: Charles Wesley Ferguson
Author: 
Author: Joseph Frank Pechanec