Recommended Citation Wurtsbaugh, Wayne A.; Heredia, Nick; Palacios, Patsy; Baker, Jared; Broderius, Chance; Fisher, Katie; Fuller, Jason; Pappas, G. Andrew; Smith, Christian; and Weston, Marc (2013) "A River Continuum Analysis of an Anthropogenically-Impacted System: The Little Bear River, Utah," Natural Resources and Environmental Issues: Vol. 18 , Article 1. Available at: https://digitalcommons.usu.edu/nrei/vol18/iss1/1
Western juniper (Juniperus occidentalis) woodlands in Oregon have expanded four-fold from 600,000 ha in 1930 to > 2.6 million ha, often resulting in the reduction and fragmentation of sagebrush (Artemisia spp.) communities. We documented dynamics of western juniper across the John Day Ecological Province in central Oregon by recording size class and growth form at 178 sites. We used stratified random sampling, with strata based on vegetation association (sagebrush, juniper, other) and distance from juniper stands. Only 26 percent of sites contained pre-settlement trees (in other words, > 140 years old), and 2.0-m tall size class (82 trees/ha), followed by the 0.3 to 1-m tall size class (52 trees/ha). These densities pose substantial risk to sagebrush communities in central Oregon. Questions remain about the extent of western juniper woodlands across the species' range that have replaced or are expanding into sagebrush communities versus sites that historically supported woodlands. However, our findings suggest that within sagebrush communities of the John Day province, intensive management through removal of western juniper may be prudent, while retaining pre-settlement trees.
Forage kochia (Kochia prostrata [L.] Schrad.) is a long-lived, perennial, half-shrub adapted to the temperate, semiarid regions of central Asia and the western U.S. In these areas it is a valuable fall/winter forage plant for sheep, goats, camels, cattle, horses, and wildlife. Forage kochia is extremely drought, heat, and salt tolerant. Forage kochia plants are very competitive with the annual noxious weeds cheatgrass (Bromus tectorum L.) and halogeton (Halogeton glomeratus [Stephen ex Bieb.] C.A. Mey.) and it is one of few species that can be successfully established on severely degraded, frequently burned, cheatgrass-infested rangelands. Forage kochia also is being used to establish greenstrips to stop the spread of wildfires, due to its high moisture content and ability to reduce the frequency of highly flammable cheatgrass. K. prostrata and K. scoparia are both sometimes referred to as forage kochia and summer cypress ; however, K. prostrata differs in that it has a perennial growth habit, does not spread into perennial plant stands, is not known to contain toxic levels of nitrates or oxalates, and increases biodiversity on rangelands. The cultivar Immigrant was released in 1984 and remains the only released cultivar of forage kochia in the U.S., and is a short-statured, diploid type, used for livestock and wildlife forage, rangeland reclamation, and suppression of wildfires. An active breeding program is underway to develop larger statured, more productive forage kochia cultivars to enhance its utilization as winter forage and habitat in the temperate deserts of the western U.S. Overall, forage kochia is not likely to become a noxious weed, but does have the potential to improve the sustainability of rangelands and wildlife habitat in semiarid regions that frequently experience extended drought, salinity, and wildfires. ____________________________________ In Monaco, T.A. et al. comps. 2011. Proceedings – Threats to Shrubland Ecosystem Integrity; 2010 May 18-20; Logan, UT. Natural Resources and Environmental Issues, Volume XVII. S.J. and Jessie E. Quinney Natural Resources Research Library, Logan Utah, USA.
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. ____________________________________ Proceedings to Integrity; Resources Issues,
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.
Wyoming shrublands have undergone extensive energy development in recent years. Much of this development occurs on public land designated for multiple uses. Reclamation of these areas has proven difficult due to the harsh climate and alteration of the thin, nutrient poor topsoil during development activities. Energy development and reclamation activities often lead to topsoil dilution, rapid mineralization of nutrients and soil organic matter (SOM), and loss of soil structure. These changes have the potential to degrade the suitability of the soil as a medium to sustain a desirable plant community. Reclamation of land disturbed for energy development in this area has largely been executed by the extraction companies and evaluated by the governing agency (typically, the Bureau of Land Management (BLM)). Other parties who rely on this land, such as ranchers with grazing permits, are not typically involved in reclamation. In this study, we examine an unconventional reclamation technique that aims to involve ranchers in the reclamation process: controlled livestock impact. The theory behind this technique is that by confining livestock on a seeded and reclaimed site the animals will improve the seedbed and seed to soil contact through fertilization and hoof action. Natural gas well pads that were reclaimed in the fall of 2009 were selected from three Wyoming natural gas fields. Two treatment plots were established on each well pad: traditionally reclaimed and reclaimed with the cattle impact treatment. Cattle treatments were applied in fall 2009 immediately after reclamation and seeding. Soil samples were taken from the reclaimed plots and before and after the cattle impact on treated plots. Soil samples were then analyzed for SOM parameters including percent light fraction organic matter (LF) and labile C and N. Post-cattle treatment plots had more mineralizable C and more N variability than pre-cattle plots, which indicates an impact from the cattle treatment on SOM characteristics. ____________________________________ In Monaco, T.A. et al. comps. 2011. Proceedings – Threats to Shrubland Ecosystem Integrity; 2010 May 18-20; Logan, UT. Natural Resources and Environmental Issues, Volume XVII. S.J. and Jessie E. Quinney Natural Resources Research Library, Logan Utah, USA.
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. ____________________________________ In Monaco, T.A. et al. comps. 2011. Proceedings – Threats to Shrubland Ecosystem Integrity; 2010 May 18-20; Logan, UT. Natural Resources and Environmental Issues, Volume XVII. S.J. and Jessie E. Quinney Natural Resources Research Library, Logan Utah, USA.
In recent years, natural gas extraction activities have disturbed thousands of acres of arid and semiarid regions in Wyoming s sagebrush steppe ecosystem. Thin, nutrient poor topsoils, combined with subsoils potentially high in salts, limit the resilience of these arid and semiarid soil systems. Stripping, stockpiling, and respreading topsoil stimulates decomposition and loss of soil organic matter (SOM) by breaking apart soil structure and eliminating inputs of plant residues,which can result in reduced SOM content When the soil structure is disturbed organic matter can rapidly decompose, releasing mineral nutrients that are mobile and can be lost to weeds, leaching, erosion, or volatilization.The purpose of this study is to gain an understanding of how natural gas development and reclamation activities impact soil properties, plant growth re-establishment, and the ability of disturbed sagebrush ecosystems to recover over time. Soil samples were collected from stockpiles,respread topsoil and adjacent undisturbed areas from three natural gas fields located in Western Wyoming. Results suggest that soil organic matter needed for plant growth becomes mineralized or released when the soil is disturbed. The data show a small increase in plant-available mineral nitrogen (N) concentrations after stripping and stockpiling compared to undisturbed soils, and then a large increase in available N following respreading for reclamation. This suggests that easily decomposable organic matter exposed by destruction of soil structure during stripping is conserved in deep stockpiles but then rapidly decomposed upon re-exposure to air and moisture with respreading. The spike in mineral N likely originates from organic compounds that,in undisturbed conditions,hold and slowly release N and other nutrients. It represents a significant potential loss of this important “time-release” nutrient pool. The spike in mineral nutrients probably stimulates prolific weed production often observed on reclaimed sites. Weeds that stay and decompose on site may conserve and recycle the nutrients, but the data suggest a need for a better way to accomplish this. ____________________________________ In Monaco, T.A. et al. comps. 2011. Proceedings – Threats to Shrubland Ecosystem Integrity; 2010 May 18-20; Logan, UT. Natural Resources and Environmental Issues, Volume XVII. S.J. and Jessie E. Quinney Natural Resources Research Library, Logan Utah, USA.
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. ____________________________________ In Monaco, T.A. et al. comps. 2011. Proceedings – Threats to Shrubland Ecosystem Integrity; 2010 May 18-20; Logan, UT. Natural Resources and Environmental Issues, Volume XVII. S.J. and Jessie E. Quinney Natural Resources Research Library, Logan Utah, USA.
The 29 papers in this proceedings are divided into the main organized sessions of the 16th Wildland Shrub Symposium, including the plenary session to introduce the theme of threats to shrubland ecosystem integrity, impacts of energy development and reclamation on ecosystem function, invasive plant ecology. wildlife habitats: impacts and restoration opportunities, historical perspectives in shrublands, ecosystem threats due to fire in the Mojave Desert, and modeling and monitoring of shrubland ecosystems. An overarching goal of the symposium was to make linkages between research and management.
