• A 40-year record of tree establishment following chaining and prescribed fire treatments in singleleaf pinyon (Pinus monophylla) and Utah juniper (Juniperus osteosperma) woodlands

      Bristow, N. A.; Weisberg, P. J.; Tausch, R. J. (Society for Range Management, 2014-07)
      Chaining and prescribed fire treatments have been widely applied throughout pinyon-juniper woodlands of the western United States in an effort to reduce tree cover and stimulate understory growth. Our objective was to quantify effects of treatment on woodland recovery rate and structure and the relative dominance of the two major tree species in our Great Basin study area, singleleaf pinyon (Pinus monophylla Torr. & Frém.) and Utah juniper (Juniperus osteosperma [Torr.] Little). We resampled plots after a 40-yr interval to evaluate species-specific differences in tree survivorship and establishment from posttreatment age structures. Tree age data were collected in 2008 within four chained sites in eastern Nevada, treated in 1958, 1962, 1968, and 1969 and originally sampled in 1971. The same data were collected at five prescribed burn sites treated in 1975 and originally sampled in 1976. All chained sites had greater juniper survival than pinyon survival immediately following treatment. Chained sites with higher tree survival also had the greatest amount of new tree establishment. During the interval between treatment and the 2008 sampling, approximately four more trees per hectare per year established following chaining than following fire. Postfire tree establishment only occurred for the initial 15 yr and was dominated by juniper. Establishment after chaining was dominated by juniper for the first 15 yr but by pinyon for 15-40 yr following treatment. Results support an earlier successional role for juniper than for pinyon, which is more dependent upon favorable microsites and facilitation from nurse shrubs. Repeated chaining at short intervals, or prescribed burning at infrequent intervals, will likely favor juniper dominance. Chaining at infrequent intervals (> 20-40 yr) will likely result in regained dominance of pinyon. Chaining treatments can be rapidly recolonized by trees and have the potential to create or amplify landscape-level shifts in tree species composition. © 2014 The Society for Range Management.
    • A Basis for Relative Growth Rate Differences Between Native and Invasive Forb Seedlings

      James, Jeremy J.; Drenovsky, Rebecca E. (Society for Range Management, 2007-07-01)
      The ability of invasive plants to achieve higher relative growth rates (RGR) than their native counterparts has been widely documented. However, the mechanisms allowing invasives to achieve higher RGR are poorly understood. The objective of this study was to determine the basis for RGR differences between native and invasive forbs that have widely invaded nutrient-poor soils of the Intermountain West. Six native and 6 invasive forbs were seeded in pots in a greenhouse, and 4 harvests were conducted over a 2-month period. These 4 harvests were used to calculate RGR and the components of RGR, net assimilation rate (rate of dry matter production per unit leaf area), leaf area ratio (LAR, leaf area per unit total plant mass), leaf mass ratio (the proportion of biomass allocated to leaves), and specific leaf area (SLA, leaf area per unit leaf biomass). Mean RGR of the 12 study species ranged between 0.04 and 0.15 g g-1 d-1 but was significantly higher for invasive forbs compared to native forbs (P = 0.036). The higher RGR achieved by invasive forbs was due mainly to a greater SLA and LAR. This indicates that invasive forbs achieved higher RGR than natives primarily by creating more leaf area per unit leaf mass, not by allocating more biomass to leaf tissue or by having a higher net rate of dry matter production. A high degree of variation in RGR, SLA, and LAR was observed in native forbs, suggesting that the ability to design weed-resistant plant communities may be improved by managing for specific functional traits as opposed to functional groups. 
    • A Case Study Evaluating Economic Implications of Two Grazing Strategies for Cattle Ranches in Northwest Argentina

      Quiroga, R. Emiliano; Blanco, Lisandro J.; Ferrando, Carlos A. (Society for Range Management, 2009-09-01)
      In the Argentinean Chaco Arido region, cattle production based on cow-calf operations is the principal source of agricultural income, and rangeland is the main forage source for cattle. Traditional grazing strategy (TGS, high stocking rate and continuous grazing) is considered the main cause of current rangeland degradation. Research shows that rangeland and cattle production improvements are possible when using a conservative grazing strategy (CGS, moderate stocking rate and rest rotation grazing). The aim of this research was to compare the effects of TGS and CGS applications on economic results for a cattle ranch in the region. To achieve this objective we used an approach that included estimations of forage and cattle production, and economic results. The study period was 1972/73–1983/84. Results showed that during the study period forage production and herd size were almost doubled with CGS, but maintained with TGS. The difference in net income between CGS and TGS (in Argentinean pesos, ), increased linearly from negative (–2.88 ha-1) to positive (4.48 ha-1) in the first 4 yr, and then was maintained at positive values (averaging 4.48 ha-1). Data suggest that CGS leads to higher productivity and better economic results than TGS in the medium and long terms. 
    • A Common-Garden Study of Resource-Island Effects on a Native and an Exotic, Annual Grass After Fire

      Hoover, Amber N.; Germino, Matthew J. (Society for Range Management, 2012-03-01)
      Plant-soil variation related to perennial-plant resource islands (coppices) interspersed with relatively bare interspaces is a major source of heterogeneity in desert rangelands. Our objective was to determine how native and exotic grasses vary on coppice mounds and interspaces (microsites) in unburned and burned sites and underlying factors that contribute to the variation in sagebrush-steppe rangelands of the Idaho National Lab, where interspaces typically have abiotic crusts.We asked how the exotic cheatgrass (Bromus tectorum L.) and native bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Lo¨ ve) were distributed among the microsites and measured their abundances in three replicate wildfires and nearby unburned areas. We conducted a common-garden study in which soil cores from each burned microsite type were planted with seed of either species to determine microsite effects on establishment and growth of native and exotic grasses. We assessed soil physical properties in the common-garden study to determine the intrinsic properties of each microsite surface and the retention of microsite soil differences following transfer of soils to the garden, to plant growth, and to wetting/drying cycles. In the field study, only bluebunch wheatgrass density was greater on coppice mounds than interspaces, in both unburned and burned areas. In the common-garden experiment, there were microsite differences in soil physical properties, particularly in crust hardness and its relationship to moisture, but soil properties were unaffected by plant growth. Also in the experiment, both species had equal densities yet greater dry mass production on coppice-mound soils compared to interspace soils, suggesting microsite differences in growth but not establishment (likely related to crust weakening resulting from watering). Coppice interspace patterning and specifically native-herb recovery on coppices is likely important for postfire resistance of this rangeland to cheatgrass./La variación suelo-planta en relación con la isla de recursos de las plantas perennes y los montículos intercalados con la presencia de inter-espacios relativamente desnudos es la mayor fuente de heterogeneidad en pastizales áridos. Nuestro objetivo fue determinar cómo pastos nativos y exóticos varían con montículos y espacios intermedios (micro-sitios) en aéreas quemadas y no quemadas, y los factores principales que contribuyen a tal variación en los pastizales de Artemisia de Idaho National Lab. Donde los inter-espacios típicamente tienen capas abióticas. Nos preguntamos cómo el pasto exótico cheatgrass (Bromus tectorum L.) y el pasto nativo bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Löve) se distribuyeron entre los micro-sitios, y medimos su abundancia en tres replicas de incendios forestales y áreas adyacentes no incendiadas. Se condujo un estudio común de jardín en el cual muestras de suelo de cada micro-sitio incendiado se sembró con semillas de cada especie para determinar el efecto de los micro-sitios en el establecimiento y crecimiento de los pastos nativos y exóticos. Las propiedades físicas del suelo se midieron como en un estudio típico de jardín para determinar las propiedades intrínsecas de la superficie de cada micro-sitio, y las diferencias en la retención de suelo en cada micro-sitio después de la transferencia de los suelos al jardín, para el desarrollo de las plantas, y para los ciclos de humectación/secado. En el primer estudio, sólo la densidad de bluebunch wheatgrass fue mayor en los montículos que en los inter-espacios en ambas áreas incendiadas y no incendiadas. En el experimento común de jardín, se presentaron diferencias en los micro-sitios relativos a las propiedades físicas del suelo, particularmente en la dureza de la corteza y su relación con la humedad, pero las propiedades del suelo no se afectaron por el crecimiento de las plantas. De igual manera en el experimento, ambas especies tuvieron iguales densidades pero mayor producción de materia seca en los suelos de los montículos comparado con los suelos de los inter-espacios, sugiriendo diferencias entre los micro-sitios en crecimiento pero no en establecimiento (probamente relacionado con el debilitamiento de la corteza como resultado del riego). Los patrones de los montículos e inter-espacios y específicamente la recuperación de herbáceas nativas en los montículos es probablemente importante para la resistencia de este pastizal a la invasión cheatgrass después de la presencia de incendios forestales.
    • A comparison of bromus tectorum growth and mycorrhizal colonization in salt desert vs. Sagebrush Habitats

      Haubensak, K. A.; D'Antonio, C. M.; Embry, S.; Blank, R. (Society for Range Management, 2014-05)
      Cheatgrass (Bromus tectorum) has recently invaded marginal low-elevation salt desert habitats across the Great Basin. We tested the hypothesis that cheatgrass seed produced in populations from the more stressful salt desert vs. upland sagebrush habitats should grow differently in salt desert soils compared to adjacent upland sagebrush soil, and vice versa. We evaluated growth, incidence of flowering, and arbuscular mycorrhizal fungi (AMF) colonization of plants grown in the soils from which their seeds were collected vs. in the reciprocal soils from the nearest sagebrush or salt desert site in three large basins in northern Nevada. Simultaneously we measured nutrient cations, available nitrogen and phosphorus, percent carbon and nitrogen, texture, and dry-down characteristics in all soils. We found that salt desert soils were generally more nutrient poor and more saline than their upland (sagebrush) counterparts; salt desert soils also generally had a higher percentage of sand compared to their upland counterparts and were consistently drier. The most dramatic plant responses to soil and seed source were 1) lower aboveground biomass of mature plants in most salt desert soils compared to sagebrush soils, or lower biomass in plants grown from salt desert seed; 2) lower root:shoot ratios in plants grown in salt desert soil across two of three basins, irrespective of seed source; 3) a higher percentage of flowering individuals from salt desert seed sources at harvest, irrespective of soil source; 4) depressed AMF colonization of plants in salt desert soils; and 5) strong influence exerted by seed source on AMF, whereby sagebrush-originating plants grown in sagebrush soils had greater AMF colonization compared to salt desert soils but salt desert-originating seedlings had very low AMF colonization rates irrespective of soil source. These results suggest that both population level and soil-based controls are important as this widespread weed moves into marginal habitat. © 2014 The Society for Range Management.
    • A comparison of satellite-derived vegetation indices for approximating gross primary productivity of grasslands

      Zhou, Y.; Zhang, L.; Xiao, J.; Chen, S.; Kato, T.; Zhou, G. (Society for Range Management, 2014-01)
      Gross primary productivity (GPP) is a key component of ecosystem carbon fluxes and the carbon balance between the biosphere and the atmosphere. Accurate estimation of GPP is essential for quantifying plant production and carbon balance for grasslands. Satellite-derived vegetation indices (VIs) are often used to approximate GPP. The widely used VIs include atmospherically resistant vegetation index, enhanced vegetation index (EVI), normalized difference greenness index, normalized difference vegetation index, reduced simple ratio, ratio vegetation index, and soil-adjusted vegetation index (SAVI). The evaluation of the performance of these VIs for approximating GPP, however, has been limited to one or two VIs and/or using GPP observations from one or two sites. In this study, we examined the relationships between the nine VIs derived from the moderate resolution imaging spectroradiometer (MODIS) and tower-based GPP at five eddy covariance flux sites over the grasslands of northern China. Our results showed that the nine VIs were generally good predictors of GPP for grasslands of northern China. Overall, EVI was the best predictor. The correlation between EVI and GPP also declined from the south to the north, indicating that EVI and GPP exhibited closer relationships in more southerly sites with higher vegetation cover. We also examined the seasonal influence on the correlation between VIs and GPP. SAVI exhibited the best correlation with GPP in spring when the grassland canopy was sparse, while EVI exhibited the best correlation with GPP in summer when the grassland cover was dense. Our results also showed that VIs could capture variations in observed GPP better in drought period than in nondrought period for an alpine meadow site because of the suppression of vegetation growth by drought. © 2014 The Society for Range Management.
    • A Critical Examination of Timing of Burning in the Kansas Flint Hills

      Gene Towne, E.; Craine, J.M. (Society for Range Management, 2016)
      Frequent burning is a crucial ecological and economic component of the Kansas Flint Hills. Although burning is important for the preservation of tallgrass prairie and improving livestock production, it has become a controversial societal issue because of its potential impact on air quality standards. Over the past 80 years, recommendations on burning in Kansas have ranged from total fire exclusion to burning only in late April; and for the past 40 years, the concept that burning should only occur in late spring has become ingrained in the cultural practices of rangeland management. Yet the scientific basis for these recommendations has received little rigorous scrutiny. Herein, we critically review the research on dormant-season burning in the Flint Hills that formed the foundation for modern burn practices in Kansas. Close examination of the historical data does not support the tenet that burning must be limited to a narrow window in late spring. Many conclusions of the research that led to recommending burning only in late spring were ambiguous, not subjected to statistical analysis, or were influenced by an antiburn bias. Current research suggests that timing of a burn is not as critical as ranchers have been led to believe and burning does not have to be restricted to a narrow window in late April. There is an absence of scientific evidence that burning earlier in the spring adversely affects forage production, plant species composition, soil moisture, or cattle weight gain. Although there is a need for research on the consequences of burning grazed pastures at different times of the year, expanding the window for burning earlier in the dormant season should help alleviate air quality issues downwind of the burned areas and potentially be beneficial to ranchers. © 2016 Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • A Direct Approach for Quantifying Stream Shading

      Clark, Patrick E.; Johnson, Douglas E.; Hardegree, Stuart P. (Society for Range Management, 2008-05-01)
      Management and regulatory standards for stream shading have been established to mitigate excessive stream temperature. Existing shade assessment tools, however, are inadequate for monitoring extensive stream networks. Our objectives were to develop and evaluate an efficient, low-cost field technique for sampling stream-surface shading using digital images and to evaluate the efficiencies and effectiveness of eight different digital image analysis techniques for shade assessments. We developed a quadrat-based technique and associated field equipment to directly photograph stream-surface shading. Sampling at random points (pixels) within the resultant digital images was the most accurate, efficient, and robust image analysis technique. An approach pairing the photographic field technique and the random point-sampling image analysis technique should enable managers to conduct ground-based assessments of stream shading over extensive stream networks. This approach may also provide an efficient means of collecting ground truth samples for even broader scale, remote sensing-based stream- shade assessments. 
    • A Fence Design for Excluding Elk Without Impeding Other Wildlife

      VerCauteren, Kurt C.; Seward, Nathan W.; Lavelle, Michael J.; Fischer, Justin W.; Phillips, Gregory E. (Society for Range Management, 2007-09-01)
      Concentrated herbivory by elk (Cervus elaphus) can degrade vegetative communities and alter ecosystem processes. Areas severely damaged by elk are commonly protected with woven wire fence, which can exclude other animals. Complete exclusion and prevention of large mammal herbivory might not always be necessary to restore vegetative communities. We designed and evaluated a simple fence that excluded elk, but maintained access for deer and other species. We enclosed a 1-ha stand of quaking aspen (Populus tremuloides Michaux) with our fence in an area with a high density of elk. We monitored effectiveness of the fence with trackplots, animal-activated cameras, and changes in aspen stem height and density. We documented only 1 elk within the exclosure in 2 years of monitoring. Mammals that used the exclosure included beaver (Castor canadensis), black bear (Ursus americanus), bobcat (Lynx rufus), coyote (Canis latrans), deer (Odocoileus spp.), mountain lion (Puma concolor), raccoon (Procyon lotor), red fox (Vulpes vulpes), and lagomorph (Leporidae). After 1 year of protection, mean aspen stem height increased 14.5 cm more inside the exclosure than outside, but stem density in the exclosure changed little compared to outside. Our fence design effectively excluded elk and has potential for protecting a variety of resources. 
    • A Landscape Similarity Index: Multitemporal Remote Sensing to Track Changes in Big Sagebrush Ecological Sites

      Hernandez, Alexander J.; Ramsey, R. Douglas (Society for Range Management, 2013-01-01)
      A similarity index for big sagebrush ecological sites was developed in northern Utah. In contrast to field measurements used to calculate similarity to reference states, our approach relies on the utilization of historic archives of satellite imagery to measure the ecological distance to benchmarks of undesired conditions such as invasion by exotic annuals and woodland encroachment. Our benchmarks consisted of locations for which there are field data collected for monitoring and evaluation purposes for several time periods. We utilized a temporal series of Landsat thematic mapper (TM) imagery that spanned 1984 to 2008 from which the soil-adjusted vegetation index (SAVI) and other transformations were extracted. Topographic and climatic variables were also included as ancillary data. Multidimensional scaling (MDS) was used to obtain scores in reduced ordination space for two periods of interest: 1984-1996 and 1997-2008. Interannual SAVI mean-variance plots provided evidence that the benchmarks and ecological sites have a distinct temporal response that allows an objective comparison. Our MDS results also show that natural clusters can be identified in the reduced statistical space for ecological sites that are a dominant component of a soil map unit. The two MDS solutions allowed the ordination of ecological sites in two gradients of productivity and bare ground. Interpretations of the transitions and trajectories of mountain, Wyoming, and basin big sagebrush sites correlated well with the ecological expectation. We anticipate that range conservationists and others actively working in rangeland evaluation can use this application to develop and update ecological site descriptions and state-and-transition models from a remotely sensed perspective.
    • A Laser Point Frame to Measure Cover

      VanAmburg, L. K.; Booth, D. T.; Weltz, M. A.; Trlica, M. J. (Society for Range Management, 2005-09-01)
      The point sample method has been a standard plotless method for measurement of ground cover on ragelands since it was introduced by Levy in 1927. The instrument most commonly used to do point sampling is the point frame. Since its introduction, the point frame has undergone numberous modifications to improve efficiency and ease of use. This article introduces a laser point frame (LPF) that was designed by the Agricultural Research Service for measurement of ground cover and utilizes lasers in place of conventional metal pins. A comparative pilot study was conducted on a shortgrass prairie in northern Colorado to compare data collected using a magnetic point frame (MPF) with data collected using the LPF. Cover by species was measured from identical plots using 100 points per plot for each point frame, and sampling times were recorded for each plot. Correlations between cover data collected using the MPF and the LPF were relatively high (r2 = 0.62-0.81). Total average vegetative cover measured with the MPF was 35%, compared with 40%, using the LPF. Cover of total grasses, C4 grasses, C3 grasses, and litter, were significantly greater with the LPF method. Total sampling time per 100 points was almost half using the LPF compared with the MPF. The LPF was easy to use, efficient for measurement of cover, and is a potential replacement for conventional point frames.
    • A Mark-Recapture Technique for Monitoring Feral Swine Populations

      Reidy, Matthew M.; Campbell, Tyler A.; Hewitt, David G. (Society for Range Management, 2011-05-01)
      Techniques to monitor populations of feral swine (Sus scrofa) relative to damage control activities are needed on rangelands. Our objectives were to describe and assess a mark-recapture technique using tetracycline hydrochloride (TH) for monitoring feral swine populations. We established bait stations at study sites in southern and central Texas. During 1 d, we replaced normal soured corn bait with bait containing TH and counted the number of feral swine that consumed bait with observers. We conducted feral swine removal using box-style traps and helicopters, at which time we collected teeth for TH analysis. In southern Texas, we estimated population reduction to be 43%. In central Texas, we estimated population reduction of 31%. Our mark-recapture population monitoring technique would complement programs to manage feral swine populations and damage through lethal control./Se necesitan técnicas para monitorear poblaciones de cerdos ferales (Sus scrofa) para actividades de control de daños en pastizales naturales. Nuestros objetivos fueron describir y evaluar una técnica de marca-recaptura utilizando hidrocloruro de tetraciclina (HT) para monitorear las poblaciones de cerdos ferales. Establecimos estaciones con cebo en las a ́reas de estudio en el sur y el centro de Tejas. Durante un día, remplazamos el cebo de maíz fermentado con cebo conteniendo HT y con observadores, contamos el número de cerdos ferales que consumieron el cebo. En el sur de Tejas, se estimó una reducción del 43% de la población. En el centro de Tejas, la reducción estimada fue del 31% de la población. Nuestra técnica de monitoreo de marca-recaptura podría complementar programas de manejo de control letal de las poblaciones de cerdos ferales y los daños que los mismos ocasionan.
    • A Method for Landscape-Scale Vegetation Assessment: Application to Great Basin Rangeland Ecosystems

      Forbis, Tara A.; Provencher, Louis; Turner, Lee; Medlyn, Gary; Thompson, Julie; Jones, Gina (Society for Range Management, 2007-05-01)
      The growth of landscape-scale land management necessitates the development of methods for large-scale vegetation assessment. Field data collection and analysis methods used to assess ecological condition for the 47 165-h North Spring Valley watershed are presented. Vegetation cover data were collected in a stratified random design within 6 Great Basin vegetation types, and the probability of detecting change in native herbaceous cover was calculated using power analyses. Methods for using these quantitative assessment data are presented to calculate a departure index based on reference condition information from LANDFIRE (an interagency effort to map and model fire regimes and other biophysical characteristics at a mid-scale for the entire United States) Biophysical Setting models for the mountain big sagebrush (Artemisia tridentata Nutt. subsp. vaseyana [Rydb.] Beetle) vegetation type. For mountain big sagebrush in the North Spring Valley landscape, we found that the earliest successional classes were underrepresented and that mountain big sagebrush moderately invaded by conifers was more abundant than predicted by the LANDFIRE reference based on the historic range of variability. Classes that were most similar to the reference were mountain big sagebrush with the highest conifer cover and late development mountain big sagebrush with perennial grasses. Overall, results suggested that restoration or approximation of the historic fire regime is needed. This method provides a cost-effective procedure to assess important indicators, including native herbaceous cover, extent of woody encroachment, and ground cover. However, the method lacks the spatial information that would allow managers to comprehensively assess spatial patterns of vegetation condition across the mosaics that occur within each major vegetation type. The development of a method that integrates field measurements of key indicators with remotely sensed data is the next critical need for landscape-scale assessment. 
    • A Nondestructive Method to Estimate Standing Crop of Purple Threeawn and Blue Grama

      Sorensen, Grant E.; Wester, David B.; Rideout-Hanzak, Sandra (Society for Range Management, 2012-09-01)
      We used multiple regression analysis to develop models to predict standing crop of purple threeawn (Aristida purpurea Nutt.) and blue grama (Bouteloua gracilis [H.B.K.] Griffiths) nondestructively. Data were collected for 3 yr on the Texas Tech University Native Rangeland, Lubbock, TX, USA. Independent variables included plant length and area measurements (basal area and cross-sectional area at a 7.5-cm plant height and at 50% of total plant height). One hundred randomly selected plants of each species were measured in June 2008; 50 plants of each species were measured in June 2009 and 2010. Coefficients of determination exceeded 0.91 for both species in all 3 yr of measurement. For both species and years, cross-sectional area at 7.5 cm was the most important single predictor variable. For each species, models differed among years. Our regression models were successful at predicting mid- to late-season standing crop of purple threeawn and blue grama grass and provide an effective method for nondestructive monitoring of these species. This approach should be applicable to similar morphotypes of these species./Usamos un análisis de regresión múltiple para desarrollar modelos no destructivos para predecir la producción de purple threeawn (Aristida purpurea Nutt.) y blue grama (Bouteloua gracilis [H.B.K.] Griffiths). Los datos fueron recolectados durante 3 años en el pastizal nativo de Texas Tech University, Lubbock TX, USA. Variables independientes incluyeron longitud de la planta, y mediciones de área (área basal y área de la sección transversal a 7.5 cm de la altura de la planta, área de la sección transversal al 50% del total de la longitud de la planta). Cien plantas de cada especie fueron seleccionadas aleatoriamente y medidas en junio de 2008; 50 plantas de cada especie fueron medidas en junio de 2009 y 2010. Los coeficientes de determinación excedieron 0.91 para ambas especies durante los tres años que se llevaron a cabo las mediciones. Para ambas especies y años, el área transversal a la altura de 7.5 cm fue la variable única de predicción más importante. Para cada especie,los modelos fueron diferentes entre años. Nuestros modelos de regresión fueron exitosos en la predicción de la biomasa en la etapa media a tardía de crecimiento de de los pastos purple threeawn y blue grama y proporcionan un método efectivo no destructivo para el monitoreo de estas especies. Esta metodología debería ser aplicable para morfo tipos similares de estas especies.
    • A Passive Application Watering System for Rangeland Plots

      Reece, Patrick E.; Koehler, Ann E.; Whisenhunt, W. Douglas; Volesky, Jerry D.; Schacht, Walter H. (Society for Range Management, 2007-03-01)
      Soil water is generally the most limiting factor for plant growth in arid and semiarid rangeland ecosystems. Interactions between precipitation regimes and optimum air temperatures for growth of different species often have measurable effects on peak standing herbage and species composition. Simulating multiple precipitation regimes in a single year will enhance our ability to quantify plant-environment interactions. Evaluating the seasonal effects of variation in timing and quantity of precipitation will require controlled water applications with little or no runoff. A diversity of plot watering systems has been developed for different kinds of agronomic and rangeland research. However, most of these systems were designed to simulate heavy pre- cipitation events and features of all previously described systems limit the number of plots and/or variation in site characteristics that can be included in rangeland field studies. Therefore, we developed the Passive Application Watering System (PAWS), which is composed of a graduated polyethylene application tank connected to a discharge system of polyvinyl chloride (PVC) and soaker hose subunits. It is portable and suitable for applying water over a wide range of slope, soil texture, and residual herbage conditions with little or no runoff. Application rates are controlled by the amount of hydrostatic pressure, which is determined by the head, the difference in height between the tank’s water level, and the soaker hoses. Heads of 0.1 m and 2.0 m produce application rates of 5 mm hr-1 and 40 mm hr-1 which correspond to the permeability of clay loam and silt loam, respectively. Application rates increase about 1.8 mm hr-1 +/- 0.15 SE for each 10-cm increase in head. We have successfully used the PAWS in 3 research projects on range sites with sandy and loamy soil texture classes. 
    • A Potential New Herbicide for Invasive Annual Grass Control on Rangeland

      Sebastian, D.J.; Sebastian, J.R.; Nissen, S.J.; Beck, K.G. (Society for Range Management, 2016)
      Downy brome (Bromus tectorum L.), a winter annual grass, is considered one of the most invasive non-native rangeland species in the United States. Although glyphosate, imazapic, and rimsulfuron are herbicides commonly recommended to control invasive, annual grasses, their performance is inconsistent and they can injure desirable perennial grasses. Indaziflam is a recently registered cellulose biosynthesis inhibiting herbicide, providing broad-spectrum control of annual grass and broadleaf weeds. Indaziflam is labeled for winter annual grass control in citrus, grape, and tree nut crops and could represent a new mode of action for selective winter annual grass control on rangeland. Three field experiments were conducted to compare indaziflam with imazapic, rimsulfuron, and glyphosate, three herbicides commonly used for downy brome control. Multiple herbicide application timings were evaluated. At all three sites, glyphosate and rimsulfuron provided less downy brome control than indaziflam 1 year after treatment (YAT). Percent downy brome control with imazapic decreased significantly 2 YAT (45-64%) and 3 YAT (10-32%). Across all sites and application timings, indaziflam provided the greatest downy brome control 2 YAT (89-100%) and 3 YAT (83-100%). Indaziflam did not significantly reduce species richness. This study demonstrates that indaziflam can provide extended downy brome control compared with currently used herbicides. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • A Process for Assessing Wooded Plant Cover by Remote Sensing

      Afinowicz, Jason D.; Munster, Clyde L.; Wilcox, Bradford P.; Lacey, Ronald E. (Society for Range Management, 2005-03-01)
      The ability to map the extent of wooded vegetation cover over large areas using remote sensing is important for managing and assessing rangelands. Currently, applied techniques are inadequate because they 1) do not directly measure the amount of land covered by woody plants and rely on low-resolution images, 2) require considerable training-area data to train a classifier, and 3) describe only a limited number of land cover types. This paper presents an innovative methodology for creating a land-cover map that requires little to no traditional, training-area data collection before classification. The procedure combines both high-resolution aerial photography (resampled to 2.5-m pixels) and lower-resolution satellite imagery (30-m pixels) to produce a detailed and easily producible data set. The resulting data set also categorizes regions into a wide variety of land cover types in addition to differing levels of wooded cover. This new methodology was applied to the Upper Guadalupe River watershed in Texas, which is composed of varying amounts of brush cover between herbaceous range and dense cover. Validation by comparison to aerial imagery demonstrated a 74.4% success rate for all land cover classes. Validation was also performed by ground survey for several brush-covered points and showed a 90.0% success rate. As a result of the ground survey, modifications to the methodology were recommended to reduce classification errors and improve the process.  
    • A Process-Based Application of State-and-Transition Models: A Case Study of Western Juniper (Juniperus occidentalis) Encroachment

      Petersen, Steven L.; Stringham, Tamzen K.; Roundy, Bruce A. (Society for Range Management, 2009-03-01)
      A threshold represents a point in space and time at which primary ecological processes degrade beyond the ability to self-repair. In ecosystems with juniper (Juniperus L. spp.) encroachment, ecological processes (i.e., infiltration) are impaired as intercanopy plant structure degrades during woodland expansion. The purpose of this research is to characterize influences of increasing juniper on vegetation structure and hydrologic processes in mountain big sagebrush-western juniper (Artemisia tridentata Nutt. subsp. vaseyana [Rydb.] Beetle-Juniperus occidentalis Hook.) communities and to identify and predict states and thresholds. Intercanopy plant cover and infiltration rates were sampled in relation to juniper canopy cover. Study plots, arranged in a randomized complete-block design, represented low shrub-high juniper, moderate shrub-moderate juniper, and high shrub-low juniper percentage of canopy cover levels at four primary aspects. In field plots, percentage of plant cover, bare ground, and steady-state infiltration rates were measured. In the laboratory, juniper canopy cover and topographic position were calculated for the same area using high-resolution aerial imagery and digital elevation data. Parametric and multivariate analyses differentiated vegetation states and associated abiotic processes. Hierarchical agglomerative cluster analysis identified significant changes in infiltration rate and plant structure from which threshold occurrence was predicted. Infiltration rates and percentage of bare ground were strongly correlated (r2 = 0.94). Bare ground was highest in low shrub-high juniper cover plots compared to both moderate and high shrub- low juniper cover levels on south-, east-, and west-facing sites. Multivariate tests indicated a distinct shift in plant structure and infiltration rates from moderate to low shrub-high juniper cover, suggesting a transition across an abiotic threshold. On north- facing slopes, bare ground remained low, irrespective of juniper cover. Land managers can use this approach to anticipate and identify thresholds at various landscape positions. 
    • A Protocol for Retrospective Remote Sensing-Based Ecological Monitoring of Rangelands

      Washington-Allen, Robert A.; West, Neil E.; Douglas Ramsey, R.; Efroymson, Rebecca A. (Society for Range Management, 2006-01-01)
      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. 
    • A Strategy for Rangeland Management Based on Best Available Knowledge and Information

      Karl, Jason W.; Herrick, Jeffrey E.; Browning, Dawn M. (Society for Range Management, 2012-11-01)
      Adapting what we currently know about ecosystems to a future where rangelands are changing is a new frontier in rangeland management. Current tools for knowledge discovery and application are limited because they cannot adequately judge ecological relevance of knowledge to specific situations. We propose development of integrated knowledge systems (KSs)—collections of resources (e.g., data, analytical tools, literature) drawn from disparate domains and organized around topics by process-based conceptual models. An integrated KS would define relevance by ecological attributes (e.g., soils, climate, vegetation) and location as a flexible mechanism for organizing, finding, and applying knowledge to rangeland management. A KS provides knowledge sources within a decision-making framework that defines what knowledge is needed and how it will be used to make decisions. Knowledge from a KS can identify appropriate spatial and temporal scales to address specific resource questions or objectives. Several factors currently limit KS development and implementation. These include limited interoperability of disparate information and knowledge systems; lack of consistent geographic referencing of knowledge; incomplete and inconsistent documentation of the origin, history and meaning of data and information; underexploited application of remote sensing products; limited ability to extrapolate and share local knowledge and unstructured information; and lack of training and education of professionals that can link ecological and technical fields of study. The proposed KS concept and recommendations present an opportunity to take advantage of emerging technologies and the collective knowledge of rangeland professionals to address changing ecosystems and evolving threats. If we keep on with a ‘‘business as usual’’ approach to finding and using information, we will struggle to meet our responsibilities as rangeland professionals./Adaptar lo que actualmente sabemos acerca de los ecosistemas a un future donde los pastizales han cambiando es una nueva frontera en el manejo de pastizales. Las herramientas que existen en la actualidad para el descubrimiento del conocimiento y su aplicación son limitadas porque no pueden juzgar adecuadamente la relevancia ecológica del conocimiento para situaciones específicas. Propusimos el desarrollo de sistemas de conocimiento integrales (Kss)--colecciones de recursos (ej., datos, herramientas analíticas, literatura) elaborado a partir de áreas diferentes y organizados en torno a temas por procesos basado en modelos conceptuales. Un KS integrado podría definir la relevancia por atributos ecológicos (ej., suelos, climas, vegetación) y la locación como un mecanismo flexible para organizar, encontrar, la aplicación de conocimiento al manejo de pastizales. Un KS provee fuentes de conocimiento dentro de un marco de toma de decisiones que define que conocimiento es necesitado y cómo va a usarse para tomar decisiones. El conocimiento de un KS puede identificar escalas espaciales apropiadas y temporales para responder preguntas de recursos específicas u objetivos. Varios factores en la actualidad limitan el desarrollo y la implementación de KS. Entre ellos encontramos: interoperabilidad limitada de información dispar y los sistemas de conocimiento. Falta de referencias geográficas consistentes del conocimiento; documentación incompleta e inconsistente de documentación de origen, historia y significado de datos e información; aplicación sin explorar de los productos de teleobservacion; habilidad limitada para extrapolar y compartir conocimiento local e información no estructurada; y entrenamiento y educación de profesionales que pueden unir los campos de estudios ecológicos y técnicos. El concepto KS propuesto y las recomendaciones son una oportunidad para aprovechar las tecnologías emergentes y el conocimiento colectivo de los pastizales para hacer frente al cambio de los ecosistemas y los riegos cambiantes. Si seguimos con un enfoque tradicional para encontrar y usar información, vamos a enfrentar serias dificultades para cumplir con nuestras responsabilidades como profesionales de los pastizales.