• Does Stocking Rate Manipulation Promote Pasture Sustainability in the Humid Tropics?

      Campbell, William Bruce; Jarillo-Rodrıguez, Jesus; Lopez-Ortiz, Silvia; Castillo-Gallegos, Epigmenio (Society for Range Management, 2013-05-01)
      Stocking rate manipulation was examined as a means of improving plant diversity (as a measure of pasture sustainability and forage value) in a native grass pasture used for dairy production in the humid tropics of Veracruz, Mexico. Given that environmental impact reduces biotic diversity, plant phylogenetic and functional diversity should decline with increased stocking rate. Stocking rates of 2, 3, and 4 cows ha-1 and a rotational grazing plan of 3 d of occupation and 27 d of rest per pasture were applied continuously over 5 yr. Across 200 quadrats in each of two replicate paddocks per treatment, observed species richness, phylogenetic diversity (average taxonomic distinctness based on species presence/absence), and functional diversity (life-cycle duration and growth habit) were assessed. Most species were forb/herbs and forb/herb-subshrubs. Perennial species declined with increased stocking rate (F=16.36, 0.05>P>0.02) while annual-perennial species increased (F=76.88, 0.01>P>0.005); the proportion of annual species was least prominent and did not differ significantly. Observed species richness and phylogenetic diversity did not differ significantly with stocking rate. The correlation between functional diversity for life-cycle duration and phylogenetic diversity was significant and positive, suggesting that plant communities were predominantly assembled randomly from the surrounding species pool rather than through interspecies interactions acting to naturally filter immigrant species, thus leading to more opportunistic and undesired species. Although grazing pressure was not sufficient to alter indices or production measures, they did reveal shifts that may precede further pasture decline, indicating pasture sustainability was not being achieved. These rapid assessment methods permit monitoring for early warnings of reductions in pasture sustainability and forage quality for cattle.
    • Economic Risks of Cheatgrass Invasion on a Simulated Eastern Oregon Ranch

      Maher, Anna T.; Tanaka, John A.; Rimbey, Neil (Society for Range Management, 2013-05-01)
      The potential of invasive plants to alter fuel properties over time has implications for the ranchers of semiarid rangelands throughout the world. A prime example of this phenomenon is the cheatgrass (Bromus tectorum L.) invasion of the native shrub steppe lands in Great Basin of the western United States. The purpose of this study is to develop a bioeconomic model that optimizes simulated ranch behavior given the beginning stages of cheatgrass invasion on a public forage allotment. The bioeconomic model is applied to a typical eastern Oregon 300 cow-calf ranch. Livestock production decisions are simulated over a 40-yr planning horizon using a multiperiod linear programming model. Results showed changes in profit-maximizing ranch management strategies in the form of decreased optimal stocking rates and forage substitution. The net present value of the simulated ranch’s income stream declined, and the probability that the ranch cannot meet its full costs of livestock production and would exit the industry increased as a result. These economic impacts were more pronounced with decreased sale price. Sensitivity analysis showed that overall results in terms of ranch behavior were specific neither to the assumed discount rate nor to the assumed percentage of cheatgrass cover (as long as this percentage is within the reference state) on the public grazing allotment. This study introduces a method for managers to quantify impacts on ranches from fuel altering invasive plants on public lands, emphasizing the importance of including information about native and invasive forage production characteristics and wildfire frequency as a function of the state of invasion.
    • Combining Glyphosate With Burning or Mowing Improves Control of Yellow Bluestem (Bothriochloa ischaemum)

      Robertson, Scott; Hickman, Karen R.; Harmoney, Keith R.; Leslie, David M. (Society for Range Management, 2013-05-01)
      The invasive yellow bluestem (Bothriochloa ischaemum [L.] Keng) threatens native biodiversity, and its control is of interest to land managers involved in restoration of invaded grasslands. We used single, double, and triple applications of glyphosate (2.125 kg ai ha-1 . application-1) over the course of one growing season in combinations at different timings (early, middle, late season) with and without a mechanical treatment of mowing or burning to determine the most effective control method. One year after treatment, burning and mowing prior to a mid-season single or double early, middle, and/or late season herbicide application resulted in a similar level of control of yellow bluestem relative to a triple herbicide application, all of which had greater control relative to herbicide treatment alone. Reproductive tiller density and visual obstruction increased 2 yr after treatment with two herbicide treatments applied either early and middle season or early and late season, but it was prevented with burning and mowing prior to herbicide application. With the exception of three herbicide applications, combining burning or mowing with herbicide applications provided more effective control of yellow bluestem than any individual herbicide applications. Burning or mowing likely improves glyphosate effectiveness by altering the invasive grass structure so that plants are clear of standing dead and have shorter, active regrowth to enhance herbicide effectiveness. During restoration projects requiring control of invasive yellow bluestem, an effective management option is a combination of mechanical and chemical control.
    • Assessing Impacts of Roads: Application of a Standard Assessment Protocol

      Duniway, Michael C.; Herrick, Jeffrey E. (Society for Range Management, 2013-05-01)
      Adaptive management of road networks depends on timely data that accurately reflect the impacts those systems are having on ecosystem processes and associated services. In the absence of reliable data, land managers are left with little more than observations and perceptions to support management decisions of road-associated disturbances. Roads can negatively impact the soil, hydrologic, plant, and animal processes on which virtually all ecosystem services depend. The Interpreting Indicators of Rangeland Health (IIRH) protocol is a qualitative method that has been demonstrated to be effective in characterizing impacts of roads. The goal of this study were to develop, describe, and test an approach for using IIRH to systematically evaluate road impacts across large, diverse arid and semiarid landscapes. We developed a stratified random sampling approach to plot selection based on ecological potential, road inventory data, and image interpretation of road impacts. The test application on a semiarid landscape in southern New Mexico, United States, demonstrates that the approach developed is sensitive to road impacts across a broad range of ecological sites but that not all the types of stratification were useful. Ecological site and road inventory strata accounted for significant variability in the functioning of ecological processes but stratification based on apparent impact did not. Analysis of the repeatability of IIRH applied to road plots indicates that the method is repeatable but consensus evaluations based on multiple observers should be used to minimize risk of bias. Landscape-scale analysis of impacts by roads of contrasting designs (maintained dirt or gravel roads vs. non- or infrequently maintained roads) suggests that future travel management plans for the study area should consider concentrating traffic on fewer roads that are well designed and maintained. Application of the approach by land managers will likely provide important insights into minimizing impacts of road networks on key ecosystem services.
    • Distinguishing Cattle Foraging Activities Using an Accelerometry-Based Activity Monitor

      Yoshitoshi, Rena; Watanabe, Nariyasu; Kawamura, Kensuke; Sakanoue, Seiichi; Mizoguchi, Ryo; Lee, Hyo-Jin; Kurokawa, Yuzo (Society for Range Management, 2013-05-01)
      Various sensors and analytic tools have been developed to assist with the collection and analysis of data regarding the activities of animals at pasture. We tested an accelerometry-based activity monitor, the Kenz Lifecorder EX (LCEX; Suzuken Co Ltd, Nagoya, Japan), to differentiate between foraging and other activities of beef cows in a steeply sloping pasture. Logistic regression (LR) and linear discriminant analysis (LDA), two of the most widely used techniques for distinguishing animal activities based on sensing device information, were employed in the analysis. An LCEX device was worn on a collar by each of four cattle over the course of 4 d, during which time the activity (foraging, resting, ruminating, walking, and grooming) of each cow was recorded by trained observers at 1-min intervals for a total of 15 h. LR and LDA were applied to the LCEX and observer data to distinguish between foraging and other activities. Overall, a more accurate measure was obtained by LDA (90.6% to 94.6% correct discrimination among cows) than by LR (80.8% to 91.8% correct discrimination). The threshold LCEX value for distinguishing between foraging and other activities varied among cows, and the correct discrimination rate for the pooled data set was 92.4% for LDA and 85.6% for LR. Based on individual cow LDA, the time spent foraging averaged between 443 and 475 min . d-1. Our results indicated that LCEX can be used to identify the foraging activity of cattle.
    • Models for Predicting Fuel Consumption in Sagebrush-Dominated Ecosystems

      Wright, Clinton S. (Society for Range Management, 2013-05-01)
      Fuel consumption predictions are necessary to accurately estimate or model fire effects, including pollutant emissions during wildland fires. Fuel and environmental measurements on a series of operational prescribed fires were used to develop empirical models for predicting fuel consumption in big sagebrush (Artemisia tridentata Nutt.) ecosystems. Models are proposed for predicting fuel consumption during prescribed fires in the fall and the spring. Total prefire fuel loading ranged from 5.3-23.6 Mgha-1; between 32% and 92% of the total loading was composed of live and dead big sagebrush. Fuel consumption ranged from 0.8-22.3 Mgha-1, which equates to 11-99% of prefire loading (mean=59%). Model predictors include prefire shrub loading, proportion of area burned, and season of burn for shrub fuels (R2=0.91). Models for predicting proportion of area burned for spring and fall fires were also developed (R2=0.64 and 0.77 for spring and fall fire models, respectively). Proportion of area burned, an indicator of the patchiness of the fire, was best predicted from the coverage of the herbaceous vegetation layer, wind speed, and slope; for spring fires, day-of-burn 10-h woody fuel moisture content was also an important predictor variable. Models predicted independent shrub consumption measurements within 8.1% (fall) and 12.6% (spring) for sagebrush fires.
    • Different Fire Frequency Impacts Over 27 Years on Vegetation Succession in an Infertile Old-Field Grassland

      Li, Wenjin; Zuo, Xiaoan; Knops, Johannes M. H. (Society for Range Management, 2013-05-01)
      We examined the effect of fire on vegetation composition with the use of an experiment with four different fire frequencies (annual, 2-yr interval, 4-yr interval, and an intended control with no burning) over a 27-yr period in an infertile, old-field grassland at the Cedar Creek Ecosystem Science Reserve, located in Minnesota, United States. We measured the plant species’ aboveground biomass in permanent plots in 1983, 1987, 1991, 2000, and 2010. None of these fire frequencies, even after 27 yr, had a large impact on the vegetation composition. The plant functional groups’ responses to fire frequency were consistent with their respective dominant species. The most abundant C4 grass, little bluestem (Schizachyrium scoparium Michx.), did not change in biomass with fire frequency over time. The biomass of the introduced, invasive grass, Kentucky bluegrass (Poa pratensis L.) decreased significantly with increasing fire frequency, but this decrease did not result in change to the rate and trajectory of vegetation change. Bush clover (Lespedeza capitata Michx.), the only legume in the community, strongly increased with more frequent fire, but only after 20 yr. Species richness and litter mass decreased significantly with increasing fire frequency. These small fire-induced vegetation changes contrast with large fire-induced vegetation changes in fertile grasslands. Management strategies using fire in infertile grasslands can lower Poa abundance; however, increased fire also decreased overall plant diversity.
    • Simulating Current Successional Trajectories in Sagebrush Ecosystems With Multiple Disturbances Using a State-and-Transition Modeling Framework

      Evers, Louisa B.; Miller, Richard F.; Doescher, Paul S.; Hemstrom, Miles; Neilson, Ronald P. (Society for Range Management, 2013-05-01)
      Disturbances and their interactions play major roles in sagebrush (Artemisia spp. L.) community dynamics. Although impacts of some disturbances, most notably fire, have been quantified at the landscape level, some have been ignored and rarely are interactions between disturbances evaluated. We developed conceptual state-and-transition models for each of two broad sagebrush groups—a warm-dry group characterized by Wyoming big sagebrush (Artemisia tridentata Nutt. subsp. wyomingensis Beetle Young) communities and a cool-moist group characterized by mountain big sagebrush (Artemisia tridentata Nutt. subsp. vaseyana [Rydb.] Beetle) communities. We used the Vegetation Dynamics Development Tool to explore how the abundance of community phases and states in each conceptual model might be affected by fire, insect outbreak, drought, snow mold, voles, sudden drops in winter temperatures (freeze-kill), livestock grazing, juniper (Juniperus occidentalis var. occidentalis Hook.) expansion, nonnative annual grasses such as cheatgrass (Bromus tectorum L.), and vegetation treatments. Changes in fuel continuity and loading resulted in average fire rotations of 12 yr in the warm-dry sagebrush group and 81 yr in the cool-moist sagebrush group. Model results in the warm-dry sagebrush group indicated postfire seeding success alone was not sufficient to limit the area of cheatgrass domination. The frequency of episodes of very high utilization by domestic livestock during severe drought was a key influence on community phase abundance in our models. In the cool-moist sagebrush group, model results indicated at least 10% of the juniper expansion area should be treated annually to keep juniper in check. Regardless, juniper seedlings and saplings would remain abundant.
    • Historical Forage Productivity and Cost of Capital for Cow-Calf Production in California

      Brownsey, Philip; Oviedo, Jose L.; Huntsinger, Lynn; Allen-Diaz, Barbara (Society for Range Management, 2013-05-01)
      Exposure of livestock grazing to forage productivity variation and to market fluctuations affects the risk of investment and returns from cow-calf operations, but little work has been done to empirically compare these returns to the returns that would be demanded by financial markets from assets with similar risk and return characteristics. This study uses historical forage production data from three rangeland locations in California, and cattle and hay prices, to simulate financial statements for three hypothetical cow-calf producers in the period 1988-2007. Return on investment from year to year incorporates the variability and risk associated with dependence on natural forage production. Performance is then compared to the actual performance of a diversified portfolio of assets using the Capital Asset Pricing Model, from which the theoretical cost of capital for these hypothetical grazing enterprises is derived. Much like other agricultural enterprises, cow-calf production in California has low market risk and a low theoretical cost of capital. This theoretical cost of capital is still greater than the historical return from livestock production (excluding land appreciation) in the western United States, adding further backing to the point often made in the literature that ranchers who engage in cow-calf production are receiving benefits beyond the commercial returns from livestock production alone.
    • Integrating Conservation and Financial Objectives on Private Rangelands in Northern Colorado: Rancher and Practitioner Perceptions

      Gutwein, Megan; Goldstein, Joshua H. (Society for Range Management, 2013-05-01)
      Payments for ecosystem services and other approaches seek to expand conservation outcomes from working ranches in rangeland systems. Making these strategies attractive to ranchers and effective in achieving conservation goals requires information that is largely lacking about the human dimensions of aligning conservation, agricultural, and financial objectives on working ranches. This exploratory study addressed this knowledge gap about perceived strategies, barriers, and opportunities by interviewing a purposive sample of 23 ranchers and natural resource practitioners (e.g., government agencies, conservation nonprofits) involved in a collaborative stakeholder group in Larimer County, Colorado. Interviewees’ responses demonstrated a wide range of potential strategies for ranchers to adopt, yet their discussion of ranch-scale and regional concerns demonstrated the multiple interlinked ecological, financial, and social factors that pose challenges for mainstreaming opportunities. All interviewees expressed interest in developing a regional payment for ecosystem services program, seeing an opportunity to simultaneously support ranchers and improve conservation stewardship. However, substantial concerns were expressed regarding possible restrictions to the ranch operation, profitability, and other management and legal factors that would diminish attractiveness to ranchers. Our findings suggest that characteristics of our study system, including proximity to urban areas and the presence of a collaborative stakeholder group, contribute importantly to the opportunities and challenges perceived by interviewees. Furthermore, interviewees’ responses highlighted how factors beyond the ranch-scale can affect the viability of ranch business strategies to achieve conservation and agricultural objectives. Future research with representative populations across rangeland systems in the American West and in contexts with and without collaborative groups will build constructively upon this exploratory study.
    • Woody Vegetation Persistence and Disturbance in Central Texas Grasslands Inferred From Multidecadal Historical Aerial Photographs

      Murray, Darrel B.; White, Joseph D.; Swint, Pamela (Society for Range Management, 2013-05-01)
      Woody vegetation encroachment has been assumed to occur uniformly over the past century across the southern Great Plains of the United States. To assess this assumption, we evaluated changes in pixels classified as woody vegetation from aerial photographs from 1937 to 2004 that were acquired approximately every 13 yr for a 7 109-ha wildlife refuge located in the eastern Edwards Plateau region of central Texas. We found that the percentage of total area classified as woody vegetation changed minimally (62.0-64.2%) from 1937 to 2004. However, on average, 32% of the study area changed classification between woody vegetation and nonwoody vegetation pixels between each photograph date. To assess potential causes of woody vegetation change, we analyzed contiguous pixels with area =1 ha and area 1 ha representing small- and large-scale disturbances, respectively. Small-scale woody vegetation pixel loss was found to be moderately low, ranging between 11.1% and 12.6% of the study area for the period of analysis, indicating relatively constant levels of canopy-level disturbance. Large-scale woody vegetation pixel loss peaked in the 1951-1964 time interval, where we identified 98 patches averaging 8.1 ha and covering 7.6% of the study area. The timing and area of these potential disturbances were correlated with drought and increased fire frequency within our study area. This methodology, which includes careful georectification and radiometric standardization of the historical photographs, can be used to detect interdecadal variability related to changes in types of disturbance over longer periods of time. This study also shows that repeated observations, such as those from aerial photographs, may be required to adequately characterize woody plant encroachment, particularly in subhumid grasslands, where disturbance and regrowth of woody plants may occur at decade time scales.
    • Fire, Defoliation, and Competing Species Alter Aristida purpurea Biomass, Tiller, and Axillary Bud Production

      Russell, M. L.; Vermeire, L. T.; Dufek, N. A.; Strong, D. J. (Society for Range Management, 2013-05-01)
      Aristida purpurea (purple threeawn) is a competitive native perennial grass with monoculturistic tendencies and poor palatability. We examined effects of fire, defoliation, and interspecific/intraspecific planting for 1) threeawn responses in the presence of threeawn, Bouteloua gracilis, or Pascopyrum smithii, and 2) B. gracilis and P. smithii response with threeawn. Biomass, aboveground production, tillers, and axillary buds were analyzed following two fire and four clipping treatments applied to three species-pair combinations in a completely randomized factorial design with nine replications. Fire killed 36% of threeawn. Fire reduced surviving threeawn biomass 61% and reduced production 27%. Threeawn production was greatest when neither plant was clipped and least when competing species were moderately clipped, or when both plants were severely clipped. Tiller counts of burned threeawn were similar among clipping treatments, and less than non-clipped or moderately clipped plants not burned. Fire decreased threeawn axillary buds on average by 25%. Moderately clipped plants had greater production than those from other clipping treatments across species. Average threeawn percentage of pot biomass was greater with B. gracilis (46+/-3% SE) than P. smithii (38+/-3% SE). Fire reduced threeawn from 60+/-3% to 23+/-3% of pot biomass, indicating good potential for rapid reductions in threeawn dominance and restoration of plant diversity with fire.
    • Aboriginal Precedent for Active Management of Sagebrush-Perennial Grass Communities in the Great Basin

      McAdoo, J. Kent; Schultz, Brad W.; Swanson, Sherman R. (Society for Range Management, 2013-05-01)
      Until recently, most contemporary ecologists have ignored or diminished anecdotal historical accounts and anthropologists’ reports about aboriginal fire in the Great Basin. Literature review shows that Indians practiced regular use of fire for many purposes, including the obvious reasons of increasing the availability of desired plants, maintaining habitats for animals used as food, and driving game during hunts. Historical accounts of prehistoric anthropogenic firing, inferences from fire scar data, and data regarding annual production capability of representative sagebrush (Artemisia spp.)-perennial grass ecological sites indicate that prehistoric conditions were neither fuel- nor ignition-limited. According to many sources, this ‘‘active management’’ by Indians was widespread, significant, and more common than lightning-caused fires, resulting in mosaic vegetation patterns that subsequently moderated the behavior of ‘‘natural fires.’’ This interaction between Indian-burning and lightning fires may have strongly influenced the pre-Euro-American settlement vegetation of the Great Basin. At the very least, the landscape was a patchwork of areas altered by aboriginal people and areas shaped primarily by bio-physical processes. Based on this prehistoric precedent, current historically unprecedented conditions (fuel load and exotic weed invasion threats), and predicted climate change, contemporary active management of sagebrush-perennial grass communities is paramount. Restoration measures should be scientifically based and tailored to achieve ecological resilience and functionality in specific sites. Prescribed fire is not always ecologically appropriate or judicious, especially in Wyoming big sagebrush (A. tridentata spp. wyomingensis) communities, so managers should consider using other alternatives where an intentional low severity distubance is deemed necessary. Properly planned active management would disrupt fuel continuity for lighthning fires, ensure ecological process and successional integrity, and benefit multiple uses on a landscape scale.
    • Hydrologic and Erosion Responses of Sagebrush Steppe Following Juniper Encroachment, Wildfire, and Tree Cutting

      Pierson, Frederick B.; Williams, C. Jason; Hardegree, Stuart P.; Clark, Patrick E.; Kormos, Patrick R.; Al-Hamdan, Osama Z. (Society for Range Management, 2013-05-01)
      Extensive woodland expansion in the Great Basin has generated concern regarding ecological impacts of tree encroachment on sagebrush rangelands and strategies for restoring sagebrush steppe. This study used rainfall (0.5 m2 and 13 m2 scales) and concentrated flow simulations and measures of vegetation, ground cover, and soils to investigate hydrologic and erosion impacts of western juniper (Juniperus occidentalis Hook.) encroachment into sagebrush steppe and to evaluate short-term effects of burning and tree cutting on runoff and erosion responses. The overall effects of tree encroachment were a reduction in understory vegetation and formation of highly erodible, bare intercanopy between trees. Runoff and erosion from high-intensity rainfall (102 mm h-1, 13 m2 plots) were generally low from unburned areas underneath tree canopies (13 mm and 48 g m2) and were higher from the unburned intercanopy (43 mm and 272 g m-2). Intercanopy erosion increased linearly with runoff and exponentially where bare ground exceeded 60%. Erosion from simulated concentrated flow was 15- to 25-fold greater from the unburned intercanopy than unburned tree canopy areas. Severe burning amplified erosion from tree canopy plots by a factor of 20 but had a favorable effect on concentrated flow erosion from the intercanopy. Two years postfire, erosion remained 20-fold greater on burned than unburned tree plots, but concentrated flow erosion from the intercanopy (76% of study area) was reduced by herbaceous recruitment. The results indicate burning may amplify runoff and erosion immediately postfire. However, we infer burning that sustains residual understory cover and stimulates vegetation productivity may provide long-term reduction of soil loss relative to woodland persistence. Simply placing cut-downed trees into the unburned intercanopy had minimal immediate impact on infiltration and soil loss. Results suggest cut-tree treatments should focus on establishing tree debris contact with the soil surface if treatments are expected to reduce short-term soil loss during the postcut understory recruitment period.
    • Site, Competition, and Plant Stock Influence Transplant Success of Wyoming Big Sagebrush

      McAdoo, J. Kent; Boyd, Chad S.; Sheley, Roger L. (Society for Range Management, 2013-05-01)
      Within the sagebrush steppe ecosystem, sagebrush plants influence a number of ecosystem properties, including nutrient distribution, plant species diversity, soil moisture, and temperature, and provide habitat for a wide variety of wildlife species. Recent increases in frequency and size of wildfires and associated annual grass expansion within the Wyoming big sagebrush alliance have increased the need for effective sagebrush restoration tools and protocols. Our objectives were to quantify the success of Wyoming big sagebrush transplants relative to transplant stock (nursery seedlings vs. wildlings) across different ecological sites and vegetation types and to test the hypothesis that reduction of herbaceous vegetation would increase survival of transplanted sagebrush. We used a randomized block (reps=5) design at each of three sites—1) cheatgrass dominated, 2) native plant dominated, and 3) crested wheatgrass dominated—near Elko, Nevada. Treatments included plant stock (nursery stock or locally harvested wildlings) and herbicide (glyphosate) to reduce competition from herbaceous vegetation. Transplants were planted in the spring of 2009 and 2010 and monitored for survival. Data were analyzed for site and treatment effects using mixed-model ANOVA. Surviving plant density at and 2 yr postplanting was generally highest (up to 3-fold) on the native site (P<0.05). Density of surviving transplants was almost 3-fold higher for nursery stock on most sites for the 2009 planting, but differences in survival by planting stock were minimal for the 2010 planting. Glyphosate application increased surviving plant density up to 300% (depending on site) for both years of planting. High labor and plant material investments (relative to traditional drilling or broadcasting) may limit the size of projects for which sagebrush transplants are practical, but these costs may be partially offset by high success relative to traditional methods. Our data indicate that sagebrush transplants can be effective for establishing sagebrush on depleted sites.