• Comparison of Unmanned Aerial Vehicle Platforms for Assessing Vegetation Cover in Sagebrush Steppe Ecosystems

      Breckenridge, Robert P.; Dakins, Maxine; Bunting, Stephen; Harbour, Jerry L.; White, Sera (Society for Range Management, 2011-09-01)
      In this study, the use of unmanned aerial vehicles (UAVs) as a quick and safe method for monitoring biotic resources was evaluated. Vegetation cover and the amount of bare ground are important factors in understanding the sustainability of many ecosystems. Methods that improve speed and cost efficiency could greatly improve how biotic resources are monitored on western lands. Sagebrush steppe ecosystems provide important habitat for a variety of species including sage grouse and pygmy rabbit. Improved methods of monitoring these habitats are needed because not enough resource specialists or funds are available for comprehensive on-the-ground evaluations. In this project, two UAV platforms, fixed-wing and helicopter, were used to collect still-frame imagery to assess vegetation cover in sagebrush steppe ecosystems. This paper discusses the process for collecting and analyzing imagery from the UAVs to 1) estimate percentage of cover for six different vegetation types (shrub, dead shrub, grass, forb, litter, and bare ground) and 2) locate sage grouse using representative decoys. The field plots were located on the Idaho National Laboratory site west of Idaho Falls, Idaho, in areas with varying amounts and types of vegetation cover. A software program called SamplePoint was used along with visual inspection to evaluate percentage of cover for the six cover types. Results were compared against standard field measurements to assess accuracy. The comparison of fixed-wing and helicopter UAV technology against field estimates shows good agreement for the measurement of bare ground. This study shows that if a high degree of detail and data accuracy is desired, then a helicopter UAV may be a good platform to use. If the data collection objective is to assess broad-scale landscape level changes, then the collection of imagery with a fixed-wing system is probably more appropriate./En este estudio se evaluó el uso de vehículos aéreos no tripulados (VANT) como un método rápido y seguro para monitorear recursos bióticos. La cubierta vegetal y la cantidad de suelo desnudo son factores importantes para entender la sustentabilidad de varios ecosistemas. Métodos que mejoren la rapidez y el costo podrían mejorar la manera en que los recursos bióticos de las tierras del oeste son monitoreados. El ecosistema de estepa de artemisa provee hábitat para varias especies que incluyen al ganso sage y conejo pigmeo. Es necesario mejorar los métodos de monitoreo de estos hábitat porque no hay suficientes especialistas en recursos o fondos disponibles para evaluaciones completas en el terreno. En este proyecto, se utilizaron dos plataformas de VANT, alas fijas y helicóptero para recolectar imágenes fotográficas para evaluar la cubierta vegetal en un ecosistema de estepa de artemisa. En este artículo se discute el proceso de recolección y análisis de imágenes de un VANT para 1) estimar el porcentaje de cubierta de seis diferentes tipos de vegetación (matorral, matorral seco, zacate, hierbas, mantillo y suelo desnudo) y 2) ubicar gansos sage usando señuelos. Las parcelas experimentales se ubicaron en el Laboratorio Nacional de Idaho sitio localizado en Idaho Falls, Idaho en áreas con diferentes cantidades y tipos de cubierta vegetal. Se uso el programa de software SamplePoint junto con inspecciones oculares para evaluar el porcentaje de cubierta de seis tipos de cubiertas. Los resultados se compararon contra medidas de campo estándar para evaluar su precisión. La comparación de la tecnología de helicóptero VANT y alas fijas contra estimaciones de campo muestra buena relación para las medidas de suelo desnudo. El estudio muestra que sí se requiere alto grado de detalle y precisión en los datos el helicóptero VANT podría ser una buena plataforma para usarse. Pero sí el objetivo de recopilación de datos, es evaluar a gran escala los niveles de cambio en el paisaje entonces, la recopilación de imágenes con el sistema de alas fijas es probablemente más apropiado.
    • Understory Vegetation and Ponderosa Pine Abundance in Eastern Oregon

      Carr, Craig A.; Krueger, William C. (Society for Range Management, 2011-09-01)
      Management prescriptions for contemporary ponderosa pine (Pinus ponderosa Dougl.) forests often incorporate the restoration to a structure that more closely resembles pre-European contact forests. Successful restoration programs should incorporate the herbaceous understory component; however, published research specifically addressing changes in understory species composition is minimal. Ponderosa pine influence on the undercanopy environment may be an important factor in understory vegetation distribution. In this study, we addressed the relationships among ponderosa pine abundance, undercanopy environment, and understory species composition and made inferences with respect to restoration potential. Data representing vegetation, soil, and environmental attributes were measured in 28 plots in an eastern Oregon ponderosa pine forest. Relationships among the parameters measured were evaluated using cluster analysis, indicator species analysis, and ordination. Ponderosa pine occupancy was inversely related to understory perennial bunchgrass abundance and species diversity and appeared to regulate the undercanopy habitat through alterations in light intensity, nitrogen availability, and soil temperature. Light availability was the most important ponderosa pine-influenced undercanopy environmental parameter associated with understory vegetation distribution. These data suggested that degradation in the undercanopy environment associated with higher levels of ponderosa pine abundance may be temporary and that restoration practices that reduce pine occupancy should promote undercanopy conditions favorable to perennial bunchgrass growth. However, understory vegetation recovery in stands with excessive pine ingrowth may be constrained by desired understory species loss or invasion by more competitive understory vegetation.
    • Contrasting Observation and Transect-Based Models of Cattle Distribution on Lincoln National Forest, New Mexico

      Halbritter, Heather; Bender, Louis C. (Society for Range Management, 2011-09-01)
      Perceptions of cattle distribution and resource conflicts are often based upon qualitative observations of cattle by managers or the general public. Such information on cattle presence and inferred habitat preferences may not reflect true habitat correlates of cattle because observations do not include any sampling design. We documented cattle presence and used presence data to model distribution of cattle with respect to landscape features on the Lincoln National Forest (LNF) of south-central New Mexico, an area of conflict with regard to cattle herbivory. We recorded cattle presence both from visual observations of cattle while conducting other research activities and from randomized pellet-group transects during the spring-autumn period when cattle grazed the high-elevation habitats. Distribution of cattle differed for several habitat variables between datasets, although distribution models from both datasets indicated that elevation, slope, distance to water and roads, and vegetation cover type most influenced cattle presence. Cattle presence was associated with a variety of cover types, and cattle were generally within 500 m of water and on slopes of < 15- 20%. Observation-based models showed positive associations with open cover types, including the strongest positive association with montane meadows, the area of conflict in LNF. In contrast, transect-based models showed positive associations with more cover types (11) than did observation-based (6). Observation-based models also showed higher association with areas closer to roads. Inferred habitat preferences based on casual observations of cattle may not accurately reflect true distribution or use, as transect-based models predicted much broader distribution throughout LNF and higher overall probabilities of cattle presence. Because cattle distribution included many other vegetation cover types in addition to montane meadows, management to enhance positive correlates of cattle distribution on LNF may be useful to alter cattle distribution away from areas of perceived conflict./Percepciones sobre la distribución del ganado y el conflicto de recursos se basan frecuentemente en observaciones cualitativas de los manejadores del ganado y el público en general. Esta información, sobre la presencia del ganado y la suposición de la preferencia de hábitat, tal vez no refleja la verdadera correlación entre hábitat y ganado por que las observaciones no incluyen un diseño de muestreo. Documentamos la presencia del ganado y usamos estos datos para modelar la distribución del mismo con respecto a las características del paisaje en Lincoln National Forest (LNF) en la parte Sur-Central de Nuevo México, en un área de conflictos que involucra el ganado. Se registro la presencia del ganado con observaciones visuales mientras se realizaban otras actividades de investigación y de transectos aleatorios grupo-pellet durante el periodo de primavera-otoño cuando, el ganado pastoreaba el hábitat de mayor elevación. La distribución del ganado difiere en diferentes variables del hábitat entre las bases de datos aunque, los modelos de distribución de ambas bases de datos indicaban la elevación, pendiente, distancia a los abrevaderos y caminos y cubierta vegetal que más influencian la presencia del ganado. La presencia del ganado fue asociada con una variedad de tipos de cubiertas y el ganado estuvo generalmente, a 500 metros del abrevadero y pendientes del 15-20%. Modelos basados en observaciones mostraron una asociación positiva con los tipos de cubierta abiertos incluyendo una fuerte asociación positiva con las praderas montane que es el área de conflicto en el LNF. En contraste, los modelos basados en transectos mostraron una asociación positiva con mas tipos de cubiertas (11) que los basados en observaciones (6). Los modelos basados en observaciones mostraron mayor asociación con áreas cerca de los caminos. Preferencias de hábitat basadas en deducciones y observaciones casuales del ganado no pueden reflejar de manera precisa la verdadera distribución o uso de la misma forma que lo hacen los modelos basados en transectos que predicen de manera más amplia la distribución a través del LNF y mayores probabilidades en general de presencia de ganado. Debido a que la distribución del ganado incluye algunos otros tipos de cubierta vegetal en adición a las praderas montane el manejo que promueva una correlación positiva en la distribución del ganado en el LNF podría ser de utilidad el alterar la distribución del ganado fuera de las áreas donde se percibe que hay conflicto.
    • Defoliation Effects on Herbage Production and Root Growth of Wet Meadow Forage Species

      Volesky, Jerry D.; Schacht, Walter H.; Koehler, Ann E.; Blankenship, Erin; Reece, Patrick E. (Society for Range Management, 2011-09-01)
      Root growth is important to the competitive ability of plants, and understanding how herbage defoliation affects root growth has implications for development of management strategies. Objectives were to determine the effects of defoliation intensity and frequency on root characteristics and herbage production of slender wheatgrass (Elymus trachycaulus [Link.] Shinners), Nebraska sedge (Carex nebrascensis C. Dewey), and ‘‘Steadfast’’ birdsfoot trefoil (Lotus corniculatus L.). Plants of each species were transplanted into containers that had been placed in the ground at wet meadow field sites the prior year. There were eight replications of a control and five defoliation treatments, which were combinations of different frequencies (two or five times) and intensities (light or heavy) and haying. Treatments were applied for a single growing season, and aboveground biomass was collected. Containers were extracted in October, and plant crowns, rhizomes, and roots were separated from the soil. Defoliation treatment did not affect total root weight, length, and surface area of Nebraska sedge or birdsfoot trefoil (P > 0.10). Slender wheatgrass total root weight was less when defoliated five times (4.46 g container-1) than when defoliated twice (6.62 g container-1) during the growing season. More frequent defoliation of slender wheatgrass also reduced length (20%) and surface area (21%) compared to less frequent defoliation. However, defoliation frequency did not affect aboveground biomass. Defoliation intensity did not affect aboveground production or root characteristics of the three species. Abundant soil moisture in meadows likely buffers negative effects of defoliation. For all species, two defoliation events (e.g., haying followed by grazing) does not appear to negatively affect root growth and herbage production.
    • Condensed Tannin in Drinking Water Reduces Greenhouse Gas Precursor Urea in Sheep and Cattle Urine

      Kronberg, Scott L.; Leibig, Mark A. (Society for Range Management, 2011-09-01)
      Ingestion of small amounts of condensed tannin (CT) by ruminants may provide benefits including reduction of ammonia and nitrous oxide emissions by reducing urine urea excretion. However, providing grazing ruminants with sufficient amounts of CT- containing forages is difficult, and an alternative may be to provide CT in their drinking water. We conducted three trials to determine if urine urea levels in sheep and cattle decrease after they drink water containing CT. In two initial trials, blood serum urea was measured as a surrogate for urine urea when lambs or steers drank tap water containing low to higher amounts of quebracho tannin (QT). Serum urea concentration was measured after lambs drank the treatments for 7 d or steers for 4-6 d. Lambs consumed pellets (16% crude protein [CP] as fed) at 3.5% of body weight, and steers were fed cubes (15% CP as fed) at 3% of body weight. Mean serum urea concentration in sheep was reduced when they consumed water with QT (P = 0.03) and was also reduced for cattle (P < 0.001). In a third trial with a Latin-square design, four wethers were fed pellets (22% CP, DM basis) and given tap water or tap water with low, medium, or high amounts of QT, and their urine urea excretion was measured. There was a linear effect of QT intake on daily urine urea excretion as a percentage of nitrogen intake (P = 0.03). Reductions in daily urea excretion as a percentage of nitrogen intake were 3.5%, 6.6%, and 12.6%, respectively, for the low, medium, and high QT intake. Small amounts of QT in the drinking water of grazing ruminants can reduce their urine urea excretion./La ingestión de pequen ̃as cantidades de taninos concentrados (TC) por los rumiantes podría traer beneficios incluyendo, la reducción de emisiones de amonia y oxido nitroso al reducir la excreción de urea por la orina. Sin embargo, proveer a los rumiantes en pastoreo con suficiente cantidad de TC en el forraje es difícil y una alternativa podría ser agregar el TC en los abrevaderos. Realizamos tres pruebas para determinar sí el nivel de urea en la orina en ovinos y bovinos disminuía después que estos animales bebieran agua con TC. En dos pruebas iniciales, se medio suero sanguino con urea como sustituto de orina de corderos y novillos que bebieron agua conteniendo baja y alta cantidad de tanino de quebracho (TQ). Se midió el suero de urea concentrado después de que los corderos bebieron del tratamiento por 7 días y los novillos de 4 a 6 días. Los corderos consumieron el 3.5% de su peso vivo de suplemento en forma de pellets (16% de PC) y los novillos suplemento en forma de cubos (15% de PC) en cantidad correspondiente al 3% de su peso vivo. La media de la concentración de suero de urea en borregas se redujo cuando consumieron agua con TQ (P = 0.03), y también se redujo en bovinos (P < 0.001). En una tercera prueba con diseño de Cuadro Latino, cuatro corderos se alimentaron con pellets (22% PC, en base a materia seca) y tuvieron acceso a agua sin TQ o agua con cantidades bajo, media y alto de TQ y se medio las excreciones de urea en la orina. Hubo un efecto linear en el consumo de TQ y las excreciones diarias de urea en la orina como un porcentaje del consumo de nitrógeno (P=0.03). La reducción de excreciones diarias de urea en la orina como porcentaje de consume de nitrógeno fueron 3.5%, 6.6%, y 12.6% respectivamente para el bajo, medio y alto consumo de TQ. Cantidades pequeñas de TQ en el agua de beber para ovinos en pastoreo puede reducir la excreción de urea en la orina.
    • Rebuttal: Disturbance to Surface Lithic Components of Archaeological Sites by Drill Seeding

      Rust, Jeffrey A.; Earl, Dale (Society for Range Management, 2011-09-01)
    • Fire and Invasive Plants Special Feature Impacts of Fire and Invasive Species on Desert Soil Ecology

      Allen, Edith B.; Steers, Robert J.; Dickens, Sara Jo (Society for Range Management, 2011-09-01)
      A review of literature shows that both fire and invasive species may cause changes in biological, chemical, and physical properties of desert soils. Although soil may recover from the impacts of fire during succession, these changes are permanent under persistent invasive species. The most severe effects of fire occur under high temperatures with high fuel buildup and soil moisture that conducts heat downward. Deserts typically have low fuel mass and low soil moisture, both conditions that would contribute to lower impacts of fire than in mesic soils. Soil is a good insulator, so soil microorganisms will survive a few centimeters deep even in hot surface fires. Immediately postfire there is often an increase in mineral nitrogen (N) and a decrease in soil carbon (C) and organic N, but these changes are often minimal in desert soils, except under fertile shrub islands that have higher fuel loads and fire temperature. Both hot and cold deserts have experienced slow recovery of native shrubs and increased growth of invasive grasses following fire. Invasive species may either increase or decrease soil N and C depending on fire temperature and site and species characteristics. Mineralization and fixation of N are often high enough after fire that subsequent productivity balances N losses. The elimination of islands of fertility coupled with postfire erosion may be a major impact after fire in grass-invaded shrub lands. In the long term, the interaction of fire and invasive species may result in more frequent fires that eliminate fertile islands and reduce the productivity of deserts. Managers may use fire as a tool to control desert invasives without the concern that N will be irrevocably lost, but this must be done judiciously to avoid eliminating shrubs and further increasing invasive species.
    • Land-Use Legacies and Vegetation Recovery 90 Years After Cultivation in Great Basin Sagebrush Ecosystems

      Morris, L. R.; Monaco, T. A.; Sheley, R. L. (Society for Range Management, 2011-09-01)
       Agricultural land use is known to alter ecological processes, and native plant communities can require decades to centuries to recover from the disturbance of cultivation. ‘‘Recovery’’ is typically measured by comparison to undisturbed adjacent sites as a control. Recovery following cultivation in sagebrush ecosystems of the Great Basin remains largely unexamined even though nearly a half million hectares of land were dry-farmed and abandoned in the early 1900s. We tested the hypothesis that the native vegetation has not recovered from this exotic disturbance by evaluating differences in canopy cover of shrubs, grasses, and forbs between paired sets of historically dry-farmed land and adjacent never-cultivated areas. Paired sites were located in three ecological sites in northwestern Utah. We found that vegetation recovery from cultivation is variable by growth form, species, and ecological site. Shrub recovery was different among sagebrush (Artemisia) species. Yellow rabbitbrush (Chrysothamnus viscidiflorus [Hook.] Nutt.) and black greasewood (Sarcobatus vermiculatus [Hook.] Torr.), which often increase following disturbance, maintained higher cover inside old fields. At one of the paired sets, shrub composition was altered from a mix of four species to dominance of mainly Wyoming big sagebrush (Artemisia tridentata Nutt. subsp. wyomingensis Beetle Young). Total forb cover was generally lower in cultivated areas and some species, such as spiny phlox (Phlox hoodii Richardson), had not recovered. The most common grass species encountered across all ecological sites, bottlebrush squirreltail (Elymus elymoides [Raf.] Swezey), had higher cover in cultivated areas. Surprisingly, exotic annual species, such as cheatgrass (Bromus tectorum L.), did not dominate these sites as they have for decades after cultivation in other areas of the Great Basin. This study demonstrates that the land-use legacy of dry farming on vegetation remains nearly a century after cultivation has ceased, and has direct implications for describing ecological site conditions. Resumen Es sabido que la actividad agr ́ıcola altera los procesos ecolo ́gicos y las comunidades de plantas nativas pueden requerir de ́cadas o siglos para recuperarse del disturbio provocado por el cultivo. La ‘‘Recuperacio ́n’’ es mide normalmente, comparando un sitio con disturbio con otro sin disturbio como control. La recuperacio ́n de los ecosistemas de artemisa del Great Basin, en los Estados Unidos de Norteame ́rica permanece sin investigar aun cuando cerca de medio millo ́n de hecta ́reas de tierra fueron abiertas al cultivo y despue ́s abandonadas a principios del 1900. Probamos la hipo ́tesis de que la vegetacio ́n nativa no se ha recuperado de ese disturbio, evaluando diferencias en la cubierta del dosel de arbustos, pastos y hierbas entre parcelas pares; una histo ́ricamente cultivada en condiciones de temporal y otra parcela adyacente nunca cultivada. Las parcelas apareadas fueron ubicadas en tres sitios ecolo ́gicos en la parte noroeste de Utah. Encontramos que la recuperacio ́n de la vegetacio ́n por efecto del cultivo es variable por formas de crecimiento, especies y sitio ecolo ́gico. La recuperacio ́n de los arbustos fue diferente entre las especies de artemisas. Las especies Chrysothamnus viscidiflorus (Hook.) Nutt. y Sarcobatus vermiculatus (Hook.) Torr. que normalmente incrementan despue ́s del disturbio mantuvieron alta cobertura en las tierras de cultivo abandonadas. En uno de los grupos de parcelas, la composicio ́n de arbustos fue dominada principalmente, por cuatro especies Artemisia tridentata Nutt. subsp. wyomingensis Beetle Young. La cubierta de hierbas fue generalmente baja en a ́reas cultivadas y algunas especies como Phlox hoodii Richardson no tuvieron recuperacio ́n. La especie de pasto comu ́nmente encontrada en todos los sitios ecolo ́gicos fue, Elymus elymoides (Raf.) Swezey que mostro alta cobertura en areas cultivadas. Sorpresivamente, especies exo ́ticas anuales como Bromus tectorum L no dominaron esos sitios como lo han hecho por de ́cadas en tierras abiertas al cultivo en otras partes de la Great Basin. Este estudio demuestra que la herencia dejada por la agricultura en condiciones de temporal se mantiene despue ́s de casi un siglo que la actividad agrı ́cola haya terminado y tiene implicaciones directas para describir la condicio ́n de sitio ecolo ́gico.
    • Fire, Plant Invasions, and Erosion Events on Western Rangelands

      Pierson, Frederick B.; Williams, C. Jason; Hardegree, Stuart P.; Weltz, Mark A.; Stone, Jeffrey J.; Clark, Patrick E. (Society for Range Management, 2011-09-01)
      Millions of hectares of rangeland in the western United States have been invaded by annual and woody plants that have increased the role of wildland fire. Altered fire regimes pose significant implications for runoff and erosion. In this paper we synthesize what is known about fire impacts on rangeland hydrology and erosion, and how that knowledge advances understanding of hydrologic risks associated with landscape scale plant community transitions and altered fire regimes. The increased role of wildland fire on western rangeland exposes landscapes to amplified runoff and erosion over short- and long-term windows of time and increases the risk of damage to soil and water resources, property, and human lives during extreme events. Amplified runoff and erosion postfire are a function of storm characteristics and fire-induced changes in site conditions (i.e., ground cover, soil water repellency, aggregate stability, and surface roughness) that define site susceptibility. We suggest that overall postfire hydrologic vulnerability be considered in a probabilistic framework that predicts hydrologic response for a range of potential storms and site susceptibilities and that identifies the hydrologic response magnitudes at which damage to values-at-risk are likely to occur. We identify key knowledge gaps that limit advancement of predictive technologies to address the increased role of wildland fire across rangeland landscapes. Our review of literature suggests quantifying interactions of varying rainfall intensity and key measures of site susceptibility, temporal variability in strength/influence of soil water repellency, and spatial scaling of postfire runoff and erosion remain paramount areas for future research to address hydrologic effects associated with the increased role of wildland fire on western rangelands.
    • Economic and Social Impacts of Wildfires and Invasive Plants in American Deserts: Lessons From the Great Basin

      Brunson, Mark W.; Tanaka, John (Society for Range Management, 2011-09-01)
      Research on the impacts of wildfire and invasive plants in rangelands has focused on biophysical rather than human dimensions of these environmental processes. We offer a synthetic perspective on economic and social aspects of wildfire and invasive plants in American deserts, focusing on the Great Basin because greater research attention has been given to the effects of cheatgrass expansion than to other desert wildfire/invasion cycles. We focus first on impacts at the level of the individual decision-maker, then on impacts experienced at the human community or larger socio-political scales. Economic impacts of wildfire differ from those of invasive grasses because although fire typically reduces forage availability and thus ranch profit opportunities, invasive grasses can also be used as a forage source and ranchers have adapted their grazing systems to take advantage of that circumstance. To reduce the threat of increased ranch bankruptcies, strategies are needed that can increase access to alternative early-season forage sources and/or promote diversification of ranch income streams by capturing value from ranch ecosystem services other than forage. The growth of low-density, exurban subdivisions in Western deserts influences not only the pattern and frequency of wildfire and plant invasions but also affects prevailing public opinion toward potential management options, and thereby the capacity of land management agencies to use those options. Outreach efforts can influence public opinion, but must be rooted in new knowledge about multiple impacts of invasion and increased wildfire in American deserts./La investigación se ha centrado en el impacto biofísico del los incendios naturales y las plantas invasoras en los pastizales, en lugar de la dimensión humana en esos procesos medioambientales. Ofrecemos una perspectiva sintética sobre aspectos económicos y sociales de los incendios naturales y las plantas invasoras en los desiertos de América, enfocándonos a la región de la Grean Basin debido a la importancia de las investigaciones sobre el efecto de la expansión del zacate cheatgrass que a otros incendios/ciclos de invasión en los otros desiertos. Nos enfocamos primero, en los impactos a nivel individual de toma de decisiones después, en los impactos experimentados a nivel comunidades humanas o escalas socio-políticas mayores. El impacto económico de los incendios naturales difiere de aquel provocado por la invasión de pastos porque, mientras el fuego reduce la disponibilidad de forraje y la oportunidad de un ingreso en el rancho, pastos invasores también pueden ser usados como fuente de forraje y los rancheros han adaptado sus sistemas de pastoreo para sacar ventaja de esta circunstancia. Para reducir el riesgo de bancarrota en el rancho, se requieren estrategias que incrementen el acceso a fuentes de alternativas de forraje al principio de la temporada y/o promover la diversificación del ingreso del rancho valorando los servicios medioambientales de éste, en lugar de solo el forraje. El crecimiento de subdivisiones ex-urbanas de baja densidad en los desiertos del Oeste, influencian no solo el patrón y frecuencia de incendios naturales e invasión de plantas sino también, afectan la opinión pública actual hacia opciones potencial de manejo y como consecuencia la capacidad de las agencias que manejan las tierras de aplicar esas opiniones. Los esfuerzos para influenciar la opinión pública tienen que estar basados en conocimiento nuevo a cerca del impacto múltiple de las invasiones y aumento de incendios naturales en los desierto de América.
    • New Rangeland Residents in Wyoming? A Survey of Exurban Landowners

      Mealer, Rachel D.; Meiman, Paul J.; Hild, Ann L; Taylor, David T.; Thompson, Jennifer S. (Society for Range Management, 2011-09-01)
      Rapid conversion of rural land to exurban development and the ensuing impacts on natural resources have been well-documented, but information about exurban landowners is lacking. To address this knowledge gap, we surveyed exurban landowners in six Wyoming counties and documented demographic characteristics, motivations, knowledge, and attitudes about natural resources and land management. The overall response rate was 55.6%. Generally, respondents were of retirement age, had lived in Wyoming for about 13 yr, and were raised in areas with a population < 10 000. Wyoming respondents lived in exurbia for the lifestyle and aesthetic values and did not expect economic gains from their property. Most respondents had knowledge about, and interest in, invasive species, water quality, landscaping, and gardening. More than half of respondents (54%) had never looked for information regarding land management. Information from this study can be used to strengthen the development and delivery of educational programs. Programs that focus on water quality or weed control likely will appeal to more exurban landowners than those that focus solely on grazing management. Our findings provide an accurate characterization of this audience and their motivations and attitudes regarding land management, and suggest that using a multipronged approach for outreach efforts, which includes both cost- and time-efficient ways to conduct important land management practices, might increase participation in educational programs.
    • Fire and Invasive Plants Special Feature Climate Change in Western US Deserts: Potential for Increased Wildfire and Invasive Annual Grasses

      Abatzoglou, John T.; Kolden, Crystal A. (Society for Range Management, 2011-09-01)
      Anthropogenic climate change is hypothesized to modify the spread of invasive annual grasses across the deserts of the western United States. The influence of climate change on future invasions depends on both climate suitability that defines a potential species range and the mechanisms that facilitate invasions and contractions. A suite of downscaled climate projections for the mid-21st century was used to examine changes in physically based mechanisms, including critical physiological temperature thresholds, the timing and availability of moisture, and the potential for large wildfires. Results suggest widespread changes in 1) the length of the freeze-free season that may favor cold-intolerant annual grasses, 2) changes in the frequency of wet winters that may alter the potential for establishment of invasive annual grasses, and 3) an earlier onset of fire season and a lengthening of the window during which conditions are conducive to fire ignition and growth furthering the fire-invasive feedback loop. We propose that a coupled approach combining bioclimatic envelope modeling with mechanistic modeling targeted to a given species can help land managers identify locations and species that pose the highest level of overall risk of conversion associated with the multiple stressors of climate change.
    • Resistance to Invasion and Resilience to Fire in Desert Shrublands of North America

      Brooks, Matthew L.; Chambers, Jeanne C. (Society for Range Management, 2011-09-01)
      Settlement by Anglo-Americans in the desert shrublands of North America resulted in the introduction and subsequent invasion of multiple nonnative grass species. These invasions have altered presettlement fire regimes, resulted in conversion of native perennial shrublands to nonnative annual grasslands, and placed many native desert species at risk. Effective management of these ecosystems requires an understanding of their ecological resistance to invasion and resilience to fire. Resistance and resilience differ among the cold and hot desert shrublands of the Great Basin, Mojave, Sonoran, and Chihuahuan deserts in North America. These differences are largely determined by spatial and temporal patterns of productivity but also are affected by ecological memory, severity and frequency of disturbance, and feedbacks among invasive species and disturbance regimes. Strategies for preventing or managing invasive plant/fire regimes cycles in desert shrublands include: 1) conducting periodic resource assessments to evaluate the probability of establishment of an altered fire regime; 2) developing an understanding of ecological thresholds associate within invasion resistance and fire resilience that characterize transitions from desirable to undesirable fire regimes; and 3) prioritizing management activities based on resistance of areas to invasion and resilience to fire.
    • Estimating Aboveground Net Primary Production in Grasslands: A Comparison of Nondestructive Methods

      Byrne, Kerry M.; Lauenroth, William K.; Adler, Peter B.; Byrne, Christine M. (Society for Range Management, 2011-09-01)
      Aboveground net primary production (ANPP) is an important ecosystem property that is affected by environmental variability. ANPP in grasslands is typically measured by clipping peak live plant material. However, this method is time intensive (and therefore expensive), making it difficult to capture spatial and temporal variability. Additionally, it is impractical to use a destructive method to estimate ANPP in long-term, permanent plots. Thus, many double-sampling techniques have been developed to reduce costs and increase sample size. The objective of our study was to assess the accuracy and precision of nondestructive techniques to estimate ANPP as supplements to the traditional method of peak biomass harvest at two grassland sites. We harvested biomass and compared estimates from the same plots to 1) canopy interception using a point frame, 2) green cover estimates derived from a digital camera, and 3) reflectance measurements using a handheld radiometer. We calculated the optimum allocation of sampling effort to direct and indirect methods to minimize sampling cost yet achieve a desired precision. We found that the point frame technique explained the highest proportion of the variability in biomass at both sites (R2 = 0.91, 0.90). However, our cost-optimization analysis revealed that the radiometer technique, although less accurate (R2 = 0.38, 0.51), could achieve a desired precision for lower labor costs than the point frame. The radiometer and point frame methods will be a useful tool for grassland ecologists and rangeland managers who desire fast, nondestructive estimates of ANPP./La producción primaria neta PPN es una propiedad importante en el ecosistema que es afectada por la variabilidad medioambiental. La PPN en pastizales se mide normalmente por medio de cortes de la parte viva de la planta. Sin embargo, este método consume mucho tiempo (y es caro) haciendo difícil estimar la variabilidad espacial y temporal. Además, es impráctico usar métodos destructivos para estimar la PPN en el largo plazo en parcelas permanentes. Por esto, técnicas de doble muestreo se han desarrollado para reducir el costo y aumentar el taman ̃ o de muestra. El objetivo de nuestro estudio fue evaluar la eficacia y eficiencia de técnicas no destructivas para estimar la PPN como complementos del método tradicional de cosecha de la biomasa en dos tipos de pastizales. Se cosecho la biomasa y se comparo las estimaciones de las mismas parcelas para 1) intercepción del dosel con el método del punto, 2) estimación de la cubierta verde derivada de una cámara digital, y 3) medidas de reflejo usando un radiómetro manual. Calculamos la ubicación óptima de esfuerzo de muestreo por métodos directos e indirectos para reducir el costo de muestreo y lograr la precisión deseada. Encontramos que la técnica del punto explico la mayor proporción de la variabilidad de biomasa en ambos sitios (R2 = 0.91, 0.90). Sin embargo, el análisis optimización-costo revelo que la técnica del radiómetro aunque menos precisa (R2 = 0.38, 0.51) podría lograr la precisión deseada con menor costo que el punto. Los métodos del radiómetro y el punto serán herramientas útiles para ecólogos y manejadores de pastizales que requieren de estimaciones de PPN rápidas y no destructivas.
    • Fire and Invasive Plants Special Feature Wildfire and Invasive Plants in American Deserts: A Special Feature

      Weltz, Mark A.; Coates-Markle, Linda; Narayanan, Rang (Society for Range Management, 2011-09-01)