Natural Resources and Environmental Issues

Field Trip Overview: Habitat Loss and Plant Invasions in Northern Utah

Justin R. Williams et al. — Fri, 16 Dec 2011 08:28:55 PST

Selection and Vegetative Propagation of Native Woody Plants for Water-Wise Landscaping

Larry A. Rupp et al. — Fri, 16 Dec 2011 08:28:54 PST

Native woody plants with ornamental characteristics such as brilliant fall color, dwarf form, or glossy leaves have potential for use in water conserving urban landscapes. Individual accessions with one or more of these unique characteristics were identified based on the recommendations of a wide range of plant enthusiasts (both professional and amateur). Documentation of these accessions has been done through locating plants on-site where possible and then developing a record based on digital photography, GPS determined latitude and longitude, and place marking of Google Earth© images. Since desirable characteristics are often unique to a single plant, utilization of these plants by the landscape industry requires that they be clonally propagated. Methods of asexual propagation including grafting, budding, layering and cuttings may be successful with native plants, but are species and even accession specific. We report on the successful cutting propagation of Arctostaphylos patula, A. pungens, and Cercocarpus intricatus, and lack of success with Juniperus osteosperma, and Mahonia fremontii.

Trend of Gardner Saltbush and Halogeton in the Lower Green River Basin, Wyoming

Sherel Goodrich et al. — Fri, 16 Dec 2011 08:28:54 PST

Displacement of Gardner saltbush (Atriplex gardneri) by halogeton (Halogeton glomeratus) is being recorded at several points in the Lower Green River Basin, Wyoming by line intercept measurements and by repeat photography. This paper gives results of the monitoring studies as of 2009. Total displacement of Gardner saltbush by halogeton has taken as little as 10 years at some locations. Loss of Gardner saltbush to halogeton has major management implications.

Seasonal Soil CO2 Flux Under Big Sagebrush (Artemisia tridentata Nutt.)

Michael C. Amacher et al. — Fri, 16 Dec 2011 08:28:53 PST

Soil respiration is a major contributor to atmospheric CO2, but accurate landscape-scale estimates of soil CO2 flux for many ecosystems including shrublands have yet to be established. We began a project to measure, with high spatial and temporal resolution, soil CO2 flux in a stand (11 x 25 m area) of big sagebrush (Artemisia tridentata Nutt.) at the Logan, Utah, Forestry Sciences Laboratory. Beginning on Nov. 1, 2009, hourly soil CO2 flux measurements were made at a single location in the stand using the Li-Cor LI-8100 soil CO2 flux instrument and 20-cm long-term chamber. Beginning in April, 2010, monthly soil CO2 flux measurements were made on a grid of 11 locations within the stand using the LI- 8100 equipped with the 20-cm survey chamber. Hourly soil temperature (10-cm depth) and volumetric soil water content data were also collected. Soil CO2 flux, temperature, and water content were highly temporally and spatially variable in the sagebrush stand. Mean (std dev) soil CO2 flux, temperature, and water content for the measurement period (November 1, 2009 - October 31, 2010) were 0.96 (0.81) umol m-2 s-1, 10.59 (10.11) deg C, and 0.101 (0.062) m3 m-3, respectively. Calculated annual soil CO2 flux obtained by summing all the hourly measurements was 328 g C m-2 y-1. For semi-arid or arid sites where precipitation is less than evapotranspiration, measured total annual soil CO2 flux will be less than the potential maximum because of dry season suppression of soil respiration when soil water content is very low.

GIS Ordination Approach to Model Distribution of Shrub Species in Northern Utah

Samuel Rivera et al. — Fri, 16 Dec 2011 08:28:52 PST

Anthropogenic and natural disturbances represent a serious threat to natural ecosystems dominated by big sagebrush (Artemisia tridentata). Conservation efforts aim to restore original species composition and prevent the invasion of undesirable species. In order to restore the historic plant communities, we need a clear understanding of how species compositions are distributed along environmental gradients. Species ordination is a process of placing plant species along environmental gradients. This study was conducted in Rich County, Utah, where substantial changes in species composition have been documented in recent years. Field data, literature review, multivariate analyzes, GIS and remote sensing techniques, and expert knowledge were used to define environmental variables and their respective suitability ranges of where shrub species may occur along this area. Ordination and CART- statistical analyzes were used to estimate and predict suitability of shrub species along environmental gradients. GIS procedures were used to spatially predict species distribution. Field data and the Southwest Regional Gap Analysis Project data provided useful information to build the model and 20 percent of field data was withheld to cross-validate the findings. Final results showed that the shrub species distribution in the rangelands of Northern Utah, specifically Rich County, might be driven by precipitation and temperature gradients -influenced greatly by elevation. Slope contributing area, NDVI, and solar radiation were statistically significant factors explaining shrub distribution. To our perception, soil moisture availability might be the most explanatory variable behind these findings. In the model validation, the Kappa coefficient was K = 61.3 percent and the overall model accuracy was 74 percent. The location of species distribution areas, in the final map, can be useful to managers in order to define where resources might be allocated to preserve and restore these native rangeland ecosystems.

Introducing Big Sagebrush into a Crested Wheatgrass Monoculture

Robert L. Newhall et al. — Fri, 16 Dec 2011 08:28:52 PST

Crested wheatgrass (Agropyron desertorum or A. cristatum) has been effectively used to stabilize arid and semi-arid range sites for decades. Reestablishing native plant materials into these areas is often desirable to increase wildlife habitat and ecological diversity. Due to its competitive nature, efforts to reestablish native plants into crested wheatgrass monocultures have had limited success. Tillage will control the grass but leaves the soil vulnerable to erosion and weed invasion. This publication will report on a trial conducted near Nephi, Utah to find a method of introducing native plants into a crested wheatgrass monoculture without subjecting the resource base to degradation in the conversion process. In this trial, the effect of chemically controlling crested wheatgrass before transplanting big sagebrush (Artemisia tridentata) was studied. Small container grown plants of sagebrush were transplanted either directly into a 60 year-old stand of crested wheatgrass or after chemically controlling the grass. Three different subspecies of big sagebrush; Basin big sagebrush (Artemisia tridentata Nutt. ssp. tridentata), Mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana (Rydb.) Beetle) and Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young); were planted to see if there would be differences among subspecies. Four years of data indicate that controlling crested wheatgrass prior to transplanting resulted in higher sagebrush survival and faster establishment. There were some differences among sagebrush subspecies. Basin big sagebrush survived equally well with or without grass control but grew faster with grass control. Chemical control of the grass was important for both the survival and growth of Mountain big sage and Wyoming big sage.

Range Management in the Face of Climate Change

James C. Catlin et al. — Fri, 16 Dec 2011 08:28:51 PST

Moderating Livestock Grazing Effects on Plant Productivity, Nitrogen and Carbon Storage

John Carter et al. — Fri, 16 Dec 2011 08:28:50 PST

Multi-year studies of plant communities and soils in the Bear River Range in southeastern Idaho and northeastern Utah found reduced ground cover and herbaceous production in areas grazed by livestock when compared to reference values or long-term rested areas. Reductions in these ecosystem components have lead to accelerated erosion and losses in stored carbon and nitrogen. Restoration of these ecosystem components, with their associated carbon and nitrogen storage, is possible by application of science-based grazing management.

Bottom-up Effects of Substrate on Two Adjacent Shrub Communities and the Distribution of a Rare and Endangered Plant Species, Astragalus jaegerianus Munz.

Barry A. Prigge et al. — Fri, 16 Dec 2011 08:28:49 PST

Edaphic habitats are botanically interesting because of differences in vegetation with neighboring sites and because they tend to harbor rare species. In the central Mojave Desert, there are granite colluvial substrates where creosote bush, the dominant shrub in the area, is sparser and generally smaller than in the neighboring creosote bush communities. It is on these sites that the Lane Mountain milkvetch, a rare and federally endangered species, is restricted. The milkvetch is a nitrogen-fixer and grows under and within the canopy of host shrubs. Our previous studies have demonstrated that the milkvetch has no preference for species of host shrub, except Larrea tridentata, which appears to be an unsuitable host plant for the milkvetch. In this study, we surveyed three transects within milkvetch habitats and three transects in adjacent creosote bush habitats in the year 2000 and again in 2010, a period coincident with long-term drought conditions in the Mojave Desert. Our results show that adjacent milkvetch and creosote bush shrub communities differ significantly in shrub height, shrub volume, and shrub density in the year 2000: the shrubs in milkvetch communities were more numerous but smaller compared to adjacent creosote bush scrub. Species richness also differed between communities in the year 2000: milkvetch communities contained 19 different shrub species and creosote bush communities had only 9 species. Surveys in 2010 show that the drought had significant negative effects on both shrub communities. Total shrub mortality (166 shrubs) was high compared to shrub recruitment (16 shrubs), and the majority of mortality and recruitment occurred in milkvetch communities (131 deaths and 16 recruits). Shrub densities decreased significantly in milkvetch communities in 2010, but were still considerably higher than in creosote bush communities. These results suggest that the restricted distribution of the Lane Mountain milkvetch may be the result of higher shrub densities in milkvetch shrub communities; increased shrub densities increases the proximity of suitable host shrubs, which in turn increase the probability of successful seed dispersal and establishment.

Synergistic Monitoring – Addressing the Threats and Identifying Opportunities

John C. Swanson et al. — Fri, 16 Dec 2011 08:28:49 PST

For many years, land managers and scientists have been applying a variety of land treatments to improve or protect rangeland ecosystems. Collectively, we have studied the response of these treatments and wildfire events to identify opportunities for maintaining or improving Nevada sagebrush ecosystem health and functionality. In partnership with collaborators, we initiated a State-wide effort to capture, consolidate, and summarize implementation, monitoring, and research information for these events. We are conducting field studies to identify and fill information gaps. We seek a new and expanded information base that is available to Nevada land managers, scientists, and others interested in healthy and resilient sagebrush sites. We plan to identify the consequences of passive and active management; develop predictive tools for adaptive management; identify research needs; and increase accessibility to location, implementation and monitoring information for these events. Through the collaborative integration of our field study results with historic and current research and monitoring information, we seek to increase knowledge of landscape-level and site-specific ecological processes. This will further develop our ability to manage and predict rangeland health, integrity, resilience (after disturbance), and resistance (to undesired change under significant disturbance regimes) in the context of multiple-use management.

Native Annual Plant Response to Fire: an Examination of Invaded, 3 to 29 Year Old Burned Creosote Bush Scrub from the Western Colorado Desert

Robert J. Steers et al. — Fri, 16 Dec 2011 08:28:48 PST

Creosote bush scrub vegetation typically contains high diversity of native annual plants relative to shrubs, cacti, perennial herbaceous species, or other plant life forms. This vegetation type is also very susceptible to exotic, invasive annual plants, which promote fire by changing fuel properties. The impact of fire on most perennial species is severe but the impact on native annual plants is not well understood. We measured annual species composition in five sites that each contained paired burned and unburned stands in the western Colorado Desert, California. The burned stands at each site ranged in time since fire from 3 to 29 years ago. Annual plant cover, species richness, and soil chemical and physical properties were compared in the paired burned and unburned reference stands. Differences between paired stands at the time of each fire are assumed negligible since shrub cover across fuel breaks did not differ prior to each fire based on aerial photographs. Fires elevated soil pH but otherwise had little effect on other soil properties. In recently burned stands, invasive annual grass abundance increased while native annual plant cover and species richness decreased. However, in older burned stands, annual plant composition did not always differ between paired stands because invasive annual plant abundance was very high in both stands. Thus, while fires can have long-lasting negative impacts to perennial components of creosote bush scrub, invasive species can displace native annual plants regardless of whether or not a site burns, although fire disturbance appears to accelerate invasive plant dominance.

Reinterpreting Historical Data for Evidence-Based Shrubland Management

Jeb C. Williamson et al. — Fri, 16 Dec 2011 08:28:47 PST

Long-term vegetation dynamics in the Chihuahuan Desert of southern New Mexico have been intensively studied for over a century, and interpretations of the broad scale drivers of these dynamics are numerous. We now understand that interpretation of spatially heterogeneous change requires a more nuanced, contextualized, and detailed understanding of edaphic features and landscape characteristics. Recently, state and transition models (STMs) have been employed to represent landscape-specific dynamics for each ecological site within a Major Land Resource Area (MLRA). We re-examined data characterizing vegetation across the public lands of the northern Chihuahuan Desert at two points in time, the 1930s and 2005. In this study, our objectives were to (1) develop geospatial data layers of historical and current vegetation states, (2) compare vegetation states between the 1930s and 2005 where the two data layers overlap, and (3) interpret any major vegetation state changes over this ~70 year period within the context of specific ecological sites. It was our hypothesis that ecological dynamics would vary in interpretable ways among ecological sites. Three primary observations are drawn from our results: (1) the bulk of the region was relatively stable during this period, (2) approximately the same amount of area experienced increased grass dominance as experienced increased shrub dominance, and (3) dynamics are strongly influenced by the properties of specific ecological sites. Major vegetation state changes, involving either increased grass dominance or increased shrub dominance, only occurred to any extent in 11 of 18 ecological sites within this study area. More important to management, significant increases in shrubs occurred within only four ecological sites. These sites were sandy, deep sand, shallow sandy, and gravelly sand. All other ecological sites within this region were relatively stable over the ~70 year period between observations. The obvious management implication is the importance of stratifying by ecological site prior to application of shrub control treatments.

Yellowstone Sage Belts 1958 to 2008: 50 Years of Change in the Big Sagebrush (Artemisia tridentata) Communities of Yellowstone National Park

Pamela G. Sikkink — Fri, 16 Dec 2011 08:28:47 PST

In 1958, 13 belt transects were established within the ungulate winter range in the northern portion of Yellowstone National Park to study how shrub communities were affected by grazing from ungulate populations. Between 1958 and 2008, the belts have been measured and photographed by different researchers at least once per decade, which has resulted in a comprehensive 50 year time series of how these communities have responded to climatic change, herbivory, and natural disturbance. In this study, we compare the percent cover, seedling establishment, and plant survival in these communities at two points in time (1958 and 2008); and explore which factors – climatic, herbivory, or disturbance – were most influential to changes in canopy cover and number of seedlings after 50 years. The recovery of the big sagebrush community after the North Fork fire is also discussed. Herbivory has controlled tree growth on the shrub belts. Climate and lack of disturbance have resulted in an increase in big sagebrush (Artemisia tridentata) cover on many shrub belts inside and outside of exclosures. Invasive annual species have become important drivers of vegetation change at the lowest elevation site.

Strategic Use of Forage Kochia (Kochia prostrata) to Revegetate Wildlife Habitat

Blair L. Waldron — Fri, 16 Dec 2011 08:28:46 PST

Estimating Historical Sage-Grouse Habitat Abundance Using a State-and-Transition Model

Louisa Evers et al. — Fri, 16 Dec 2011 08:28:45 PST

Use of reference conditions to compare current conditions what managers believed represented healthy and functioning systems has become a common approach to evaluate vegetation and habitat conditions and aid development of land management plans. Often reference conditions attempt to describe landscapes as they existed and functioned prior to about 1850, and often largely rely on expert opinion. We developed reference conditions for sagebrush (Artemisia spp. L.) ecosystems in eastern Oregon based on ecological site descriptions, soil surveys, climate data, wildfire records, expert opinion, and literature using a state-and-transition (STM) modeling framework. Using ecological site descriptions for the Malheur High Plateau Major Land Resource Area (MHP), we divided sagebrush communities into four groups based on grass productivity in low, average and high productivity years. Literature helped us determine which disturbance factors to include, the community phases for each model, and associated seasonal habitat for greater sage-grouse (Centrocercus urophasianus). We developed successional timelines in the absence of disturbance, and determined the probable outcomes of a given type of disturbance event. We used fire records and climate data to develop disturbance event probabilities and periodicities. Contrary to our expectations, fire did not appear to be the most important factor influencing sagebrush ecosystems under reference conditions in our models. The modeled historical abundance of sage-grouse breeding and brood-rearing habitat was within range of or greater than the amount recommended by sage-grouse biologists, but the abundance of wintering habitat was less. By using objective criteria as much as possible, our approach should also be repeatable in other locations. Since we used climate criteria to define most disturbance probabilities, our models provide an opportunity to examine how changes in climate could affect plant communities, disturbance regimes, and the quality and quantity of sage-grouse habitat in future modeling efforts.

Potential Impacts of Energy Development on Shrublands in Western North America

Amy Pocewicz et al. — Fri, 16 Dec 2011 08:28:44 PST

Impending rapid development of the abundant energy resources found in western North America may have dramatic consequences for its terrestrial ecosystems. We used lease and license data to provide an approximate estimate of direct and indirect potential impacts from renewable and non-renewable energy development on each of five major terrestrial ecosystems and completed more detailed analyses for shrubland ecosystems. We found that energy development could impact up to 21 percent (96 million ha) of the five major ecosystems in western North America. The highest overall predicted impacts as a percent of the ecosystem type are to boreal forest (23-32 percent), shrublands (6-24 percent), and grasslands (9-21 percent). In absolute terms, the largest potential impacts are to shrublands (9.9 to 41.1 million ha). Oil, gas, wind, solar, and geothermal development each have their greatest potential impacts on shrublands. The impacts to shrublands occur in all ecological regions across western North America, but potential impacts are greatest in the North American Deserts (up to 27 percent or 25.8 million ha), Great Plains (up to 24 percent or 8.9 million ha), and Northern Forests (up to 47 percent or 4.3 million ha). Conventional oil and gas development accounts for the largest proportion of the potential impact in all three of these regions. Some states or provinces may experience particularly large impacts to shrublands, including Alberta and Wyoming, where potential for oil and gas development is especially high, and New Mexico, where solar development could potentially affect large areas of shrubland. Understanding the scale of anticipated impacts to these ecosystems through this type of coarse-scale analysis may help to catalyze policy makers to engage in proactive planning.

Impacts of Fire on Sage-grouse Habitat and Diet Resources

Jon D. Bates et al. — Fri, 16 Dec 2011 08:28:44 PST

Predicting the Impact of Climate Change on Cheat Grass (Bromus tectorum) Invasibility for Northern Utah: A GIS and Remote Sensing Approach

Samuel Rivera et al. — Fri, 16 Dec 2011 08:28:43 PST

Cheat grass (Bromus tectorum) invasibility represents a serious threat to natural ecosystems dominated by sagebrush (Artemisia tridentata). Ecosystem susceptibility to annual grass invasion seems to be driven by specific biophysical conditions. The study was conducted in Rich County, Utah, where cheat grass invasion is not yet an apparent problem, but an imminent invasion might be just a matter of time (temporal scale) to meet spatial variations in environmental conditions (spatial scale). Literature review and expert knowledge were used to define biophysical variables and their respective suitability ranges of where cheat grass takeover might occur. GIS, remote sensing and logistic regression-statistical analyses were employed to estimate probability of cheat grass invasion along environmental gradients. GIS procedures were used to spatially predict areas prone to be invaded by cheat grass under present climatic conditions (model prediction power was 47 percent). Afterwards, simulated climatic change projections (for 2099 year) from the Community Climatic System Model (CCSM-3) were used to model the invasibility risk of cheat grass. The 2099 cheat grass prediction map showed a favorable reduction of around 25 percent in the areas affected by cheat grass invasion, assuming that climate changes occurred as predicted by the CCSM model. The location of highly predisposed areas can be useful to alert managers and define where resources might be allocated to reduce a potential invasion and preserve native rangeland ecosystems.

Associations of Near-Surface Soil Moisture and Annual Plant Community Dynamics

Lauren P. Ducas et al. — Fri, 16 Dec 2011 08:28:42 PST

Invasive species have become an increasingly large concern, particularly in already degraded ecosystems, such as sagebrush (Artemisia tridentata)-steppe of the Intermountain West. Much of this ecosystem is already infested with large cheatgrass (Bromus tectorum) stands and is potentially at risk for future invasions depending on biotic and abiotic conditions. In these ecosystems, the existing vegetation, whether native or non-native, may not effectively utilize the soil moisture resources in the upper portion of the soil, termed the growth pool. If the existing vegetation does not effectively utilize moisture in the growth pool, an open resource is left for the establishment of other plants, including invasives. Through a combination of soil moisture modeling and observational studies, we identified three potential invasion pathways, particularly by annual plants, into a cheatgrass-dominated system, all consistent with the fluctuating resource hypothesis, and all resulting from an available water resource in the growth pool. Results suggest these arid and semi-arid systems are likely to be protected from novel invasive species by complete utilization of growth pool soil water resources by any existing vegetation, whether native or non-native. Our results also suggest the same features which make the site more prone to novel annual invaders may also be useful in guiding establishment of desired vegetation during restoration efforts.

Morphological and Physiological Traits Account for Similar Nitrate Uptake by Crested Wheatgrass and Cheatgrass

A. Joshua Leffler et al. — Fri, 16 Dec 2011 08:28:41 PST

Millions of hectares throughout the Intermountain West are either dominated or threatened by the invasive annual grass Bromus tectorum (cheatgrass). This invasion is largely linked to disturbance and few regions appear immune. Disturbance liberates resources in a community and cheatgrass appears exceptionally able to capitalize on these resources. One species, however, is consistently competitive with cheatgrass. Agropyron cristatum (crested wheatgrass), an improved plant material developed from several populations in central Asia, is drought resistant, grazing tolerant, and largely excludes cheatgrass in stands established within the Great Basin. While previous studies document high resource uptake ability by crested wheatgrass, it remains unknown if high uptake in this species is due to morphological or physiological adaptation. We examined N uptake and tissue morphology of four grasses common in the Intermountain West, including cheatgrass and crested wheatgrass. We also included two native grasses, Pseudoroegneria spicata (bluebunch wheatgrass) and Elymus elymoides (bottlebrush squirreltail). We observed similar rates of N uptake by cheatgrass and crested wheatgrass and their uptake was greater than the native perennial species. A multivariate analysis suggests that, of the three perennial grasses examined here, crested wheatgrass is morphologically most similar to cheatgrass, but that morphology only accounts for 57 percent of the variation in N uptake capacity among species. Consequently, physiological traits such as induction of N uptake or N efflux likely play a role in the ability of crested wheatgrass to achieve N uptake rates similar to cheatgrass.