US Rangelands Research Articles

Ecosystem Impacts of Exotic Plants Can Feed Back to Increase Invasion in Western US Rangelands

Ecosystem Impacts of Exotic Plants Can Feed Back to Increase Invasion in Western US Rangelands DOI:10.2458/azu_rangelands_v32i1_Hawkes

Ecosystem Impacts of Exotic Plants Can Feed Back to Increase Invasion in Western US Rangelands

Ecosystem Impacts of Exotic Plants Can Feed Back to Increase Invasion in Western US Rangelands

Ecosystem Impacts of Exotic Plants Can Feed Back to Increase Invasion in Western US Rangelands

Ecosystem Impacts of Exotic Plants Can Feed Back to Increase Invasion in Western US Rangelands

A Protocol for Retrospective Remote Sensing–Based Ecological Monitoring of Rangelands

The degree of rangeland degradation in the United States is unknown due to the failure of traditional field-based monitoring to capture the range of variability of ecological indicators and disturbances, including climatic effects and land use practices, at regional to national spatial scales, and temporal scales of decades. Here, a protocol is presented for retrospective monitoring and assessment of rangeland degradation using historical time series of remote sensing data and catastrophe theory as an ecological framework to account for both gradual and rapid changes of state. This protocol 1) justifies the use of time-series satellite imagery in terms of the spatial and temporal scale of data collection; 2) briefly explains how to acquire, process, and transform the data into ecological indicators; 3) discusses the use of time-series analysis as the appropriate procedure for detecting significant change; and 4) explains what reference conditions are appropriate. Landsat data have been collected and archived since 1972, and include complete coverage of US rangelands. Characteristics of land degradation can be retrospectively measured for a nearly 33-year trend using surrogate remote sensing–based indicators that correlate with changes in life-form composition (time series of thematic maps), declines in vegetation productivity (vegetation indices), accelerated soil erosion (soil indices), declines in soil quality (piospheric analysis), and changes in landscape configuration (time series of thematic maps). Aspects of 2 retrospective studies are presented as examples of application of the protocol to considerations of the land use impacts from military training and testing and ranching activities on rangelands. El grado de degradación de los pastizales en los Estados Unidos de América es desconocido debido al fracaso del monitoreo tradicional de campo para capturar el rango de variabilidad de los indicadores ecológicos y disturbios, incluyendo los efectos climáticos y prácticas de uso de la tierra, a escalas espaciales de regional a nacional y escalas temporales de décadas. Consecuentemente, es presentado un protocolo para el monitoreo retrospectivo y la evaluación de la degradación de los pastizales usando series de tiempo históricas de sensores remotos y la teoría de catástrofe como un marco ecológico para cuantificar tanto los cambios graduales como los rápidos del estado del pastizal. Este protocolo: 1) justifica el uso de series de tiempo de imágenes de satélite en términos de escalas espacial y temporal de colección de datos; 2) explica brevemente como adquirir, procesar y transformar los datos en indicadores ecológicos; 3) discute el uso del análisis de series de tiempo como un procedimiento adecuado para detectar cambios significativos; y 4) explica que condiciones de referencia son apropiadas. Datos de Landsat han sido colectados y archivados desde 1972 e incluyen una cobertura completa de los pastizales de Estados Unidos de América. Las características de la degradación de la tierra pueden ser medidas retrospectivamente para una tendencia de casi 33 años usando indicadores de remplazo basados en sensores remotos que se correlacionan con cambios en la composición de las formas de vida (series de tiempo de mapas temáticos), disminuciones en la productividad de la vegetación (índices de vegetación), erosión acelerada del suelo (índices de suelo), disminución de la calidad del suelo (análisis piosférico) y cambios en la configuración del paisaje (series de tiempo de mapas temáticos). Se presentan aspectos de dos estudios retrospectivos como ejemplo de la aplicación del protocolo para consideraciones de los impactos del uso de la tierra en entrenamiento y pruebas militares y actividades de rancho en los pastizales.

A Protocol for Retrospective Remote Sensing-Based Ecological Monitoring of Rangelands

The degree of rangeland degradation in the United States is unknown due to the failure of traditional field-based monitoring to capture the range of variability of ecological indicators and disturbances, including climatic effects and land use practices, at regional to national spatial scales, and temporal scales of decades. Here, a protocol is presented for retrospective monitoring and assessment of rangeland degradation using historical time series of remote sensing data and catastrophe theory as an ecological framework to account for both gradual and rapid changes of state. This protocol 1) justifies the use of time-series satellite imagery in terms of the spatial and temporal scale of data collection; 2) briefly explains how to acquire, process, and transform the data into ecological indicators; 3) discusses the use of time-series analysis as the appropriate procedure for detecting significant change; and 4) explains what reference conditions are appropriate. Landsat data have been collected and archived since 1972, and include complete coverage of US rangelands. Characteristics of land degradation can be retrospectively measured for a nearly 33-year trend using surrogate remote sensing-based indicators that correlate with changes in life-form composition (time series of thematic maps), declines in vegetation productivity (vegetation indices), accelerated soil erosion (soil indices), declines in soil quality (piospheric analysis), and changes in landscape configuration (time series of thematic maps). Aspects of 2 retrospective studies are presented as examples of application of the protocol to considerations of the land use impacts from military training and testing and ranching activities on rangelands.

Can spring cattle grazing among young bitterbrush stimulate shrub growth?

Abstract Due to its palatability and forage quality, antelope bitterbrush (Purshia tridentata Pursh DC) is a desirable shrub across western US rangelands. Because little information is available regarding grazing management of young bitterbrush, a study was undertaken to explore stocking pressure thresholds and quantify effects of light and heavy spring cattle grazing on shrub growth. Rates of browsing and trampling and forage availability were monitored over 3 years in southeast Oregon. Across years, 29% of bitterbrush endured trampling in light-grazing treatments, and 55% experienced trampling under heavy grazing. Linear models relating time and cattle density successfully explained (r2 = 0.84–0.86) probabilities of bitterbrush being trampled. Forage utilization averaged 32% and 59% in lightly and heavily grazed units, and 14 and 62% of bitterbrush were browsed in lightly and heavily-grazed pastures, respectively. Cattle began browsing when herbaceous standing crop declined to 100–150 kg ha−1. Browsing ...

Can spring cattle grazing among young bitterbrush stimulate shrub growth?

Due to its palatability and forage quality, antelope bitterbrush (Purshia tridentata Pursh DC) is a desirable shrub across western US rangelands. Because little information is available regarding grazing management of young bitterbrush, a study was undertaken to explore stocking pressure thresholds and quantify effects of light and heavy spring cattle grazing on shrub growth. Rates of browsing and trampling and forage availability were monitored over 3 years in southeast Oregon. Across years, 29% of bitterbrush endured trampling in light-grazing treatments, and 55% experienced trampling under heavy grazing. Linear models relating time and cattle density successfully explained (r2 = 0.84-0.86) probabilities of bitterbrush being trampled. Forage utilization averaged 32% and 59% in lightly and heavily grazed units, and 14 and 62% of bitterbrush were browsed in lightly and heavily-grazed pastures, respectively. Cattle began browsing when herbaceous standing crop declined to 100-150 kg ha-1. Browsing in heavily-grazed pastures reduced diameters of bitterbrush by 4.5 to 9.5 cm in 1998 and 1999, but shrub height was unaffected. Lightly-grazed stands exhibited a 50% greater increase in bitterbrush diameter, 30% greater height increment, and 8% longer twigs than shrubs in ungrazed pastures. At the end of the 1997 and 1998 growing seasons, bitterbrush in heavily-grazed pastures were 11 cm greater in diameter than ungrazed controls and equal to shrubs in lightly-grazed pastures. To stimulate bitterbrush growth, young stands can be lightly-grazed (30 to 40% utilization of herbaceous forage) by cattle when bitterbrush is flowering and accompanying grasses are in vegetative to late-boot stages of phenology.

An ecosystem perspective on grasshopper control: possible advantages to no treatment

Abstract It has been hypothesized that some herbivores may increase the cycling of nutrients in ecosystems, thereby increasing plant production even after herbivore consumption is considered. Such herbivory could maintain the productivity of ecosystems and should not be curtailed. This contrasts with the traditional view whereby herbivory always reduces plant production. Two grasshoppers (Melanoplus sanguinipes and Ageneotettix deorum), considered pest species in Western US rangelands, are experimentally shown to enhance plant production under certain conditions and to diminish it under others. Plant production increased when grasshoppers' consumption increased nitrogen cycling, nitrogen being the limiting resource for plants at the study sites. This happened when grasshoppers consumed plant species with slowly decomposing litter, favoring plants whose litter decomposed rapidly, such that their store of nitrogen was more rapidly released to the soil. However, feeding preferences change between sites and w...

Soil carbon dynamics and potential carbon sequestration by rangelands

The USA has about 336 Mha of grazing lands of which rangelands account for 48%. Changes in rangeland soil C can occur in response to a wide range of management and environmental factors. Grazing, fire, and fertilization have been shown to affect soil C storage in rangelands, as has converting marginal croplands into grasslands. Carbon losses due to soil erosion can influence soil C storage on rangelands both by reducing soil productivity in source areas and potentially increasing it in depositional areas, and by redistributing the C to areas where soil organic matter mineralization rates are different. Proper grazing management has been estimated to increase soil C storage on US rangelands from 0.1 to 0.3 Mg C ha −1year −1 and new grasslands have been shown to store as much as 0.6 Mg C ha −1year −1. Grazing lands are estimated to contain 10–30% of the world’s soil organic carbon. Given the size of the C pool in grazing lands we need to better understand the current and potential effects of management on soil C storage.

Conditioned food aversions: principles and practices, with special reference to social facilitation.

Conditioned food aversion is a powerful experimental tool to modify animal diets. We have also investigated it as a potential management tool to prevent livestock from grazing poisonous plants such as tall larkspur (Delphinium barbeyi), white locoweed (Oxytropis sericea) and ponderosa pine (Pinus ponderosa) on western US rangelands. The following principles pertain to increasing the strength and longevity of aversions: mature animals retain aversions better than young animals; novelty of the plant is important, although aversions can be created to familiar plants; LiCl is the most effective emetic, and the optimum dose for cattle is 200 mg/kg body weight; averted animals should be grazed separately from non-averted animals to avoid the influence of social facilitation which can rapidly extinguish aversions. Social facilitation is the most important factor preventing widespread application of aversive conditioning. When averted animals see other animals eat the target food they will sample it, and if there is no adverse reaction they will continue eating and extinguish the aversion. However, if averted animals can be grazed separately, aversions will persist. Aversive conditioning may provide an effective management tool to prevent animals from eating palatable poisonous plants that cause major economic loss.

Selenium-induced "blind staggers" and related myths. A commentary on the extent of historical livestock losses attributed to selenosis on western US rangelands.

,~~~,~~~ Signs of acute toxicity appear in diets containing selenium in excess of 5 ~pm.’~~ A common form of acute selenosis in cattle, sheep, and pigs at present is accidental overs~pplementation.~~.~~J~~J~~J~~ Concern about spontaneous forms of selenosis reemerged in the early 1980s due to a controversy about the extent and significance of losses in waterfowl at the Kesterson Wildlife Refuge in California, following contamination of irrigation wastewater by selenium.L07J21J22 Wildlife biologists concluded that deaths and teratogenic effects in wildfowl were due to selenosis, and regulatory agencies subsequently tightened regulations intended to restrict the exposure of people, domestic animals, and wildlife to se1enium.l The Federal Drug Administration recently attempted unsuccessfully to reduce the approved level of selenium in animal feeds from 0.3 to 0.1 mg/kg (dry Amended regulations have potentially significant implications for producers in selenium-deficient areas, and for imgation district^^^,^^ and mining industrie~~~,~~,~~ in seleniferous areas. Reviewers of the extent of selenosis in people living in seleniferous areas in the United States conclude that the problem is ~are.~O.~’ A localized problem developed under unusual circumstances in people in one area of China.163 Notwith