• Long-Term Livestock Exclusion in an Arid Grassland Alters Vegetation and Soil

      Allington, Ginger R. H.; Valone, Thomas J. (Society for Range Management, 2011-07-01)
      Changes in soil and vegetation due to livestock grazing are occurring in arid lands throughout the world. The most extreme cases result in desertification, which is seen as largely irreversible, because of altered soil properties. To understand better how long-term livestock removal affects soil properties and vegetation, we compared water-infiltration rates, soil bulk density, and perennial grass cover inside and outside a long-term livestock exclosure in an arid grassland site in southeastern Arizona, United States. The site had not been desertified at the time of this study. Exclusion of livestock for 40 yr was associated with lower bulk density and higher water infiltration in both the dry and wet seasons. Perennial grass cover was higher and two native grasses, Eragrostis intermedia and Bouteloua hirsuta were significantly more common (P < 0.05) in the ungrazed area. These findings parallel our results from a desertified site and suggest that changes in soil physical properties associated with long-term livestock removal are not an artifact of desertification and can take place in a system that has remained in a grassland state. Our data suggest that, although significant changes in species composition have occurred, this grassland is relatively resilient to substantial changes in soil physical properties.
    • Fire History of a Relict Oak Woodland in Northeast Texas

      Stambaugh, Micheal C.; Sparks, Jeff; Guyette, Richard P.; Willson, Gary (Society for Range Management, 2011-07-01)
      Empirical data generated from fire scars are a foundation for understanding fire regimes, designing land-management objectives, and addressing long-term land-use and climate-change effects. We derived precise dates of historic fires from fire-scar injuries occurring on trees growing in a relict post oak woodland in northeastern Texas. The fire-event chronology shows the last three centuries were marked with human influence, with an overall trend of decreasing fire occurrence through time. Thirty different fire events occurred between 1690 and 2007, of which 26 occurred prior to 1856. All fires occurred while trees were dormant. From 1690 to 1820, the mean fire interval was 6.7 yr. A 50-yr period without fire occurred in the latter 19th century (1855-1905) and coincided with the establishment of an oak cohort. A second extended period (80 yr) without fire characterized most of the 20th century. We hypothesize that the absence of fire during much of the last century has resulted in increased tree density and canopy closure, the establishment of fire-intolerant vines, shrubs, and trees, and likely the decline of fire-dependent plant species. Information describing long-term changes of fire regimes in oak woodlands in this region could aid in determining fire-management objectives with respect to prescribed fire implementation and community restoration.
    • Homogenization of the Soil Surface Following Fire in Semiarid Grasslands

      White, Carleton S. (Society for Range Management, 2011-07-01)
      Semiarid grasslands accumulate soil beneath plant ‘‘islands’’ that are raised above bare interspaces. This fine-scale variation in microtopographic relief is plant-induced and is increased with shrub establishment. Research found that fire-induced water repellency enhanced local-scale soil erosion that reduced variation in microtopographic relief, suggesting that fire may counteract vegetation-driven, fine-scale spatial soil heterogeneity. This article analyzes longer-term measurements (up to 9 yr) of soil microtopography to evaluate the hypothesis that fire in semiarid grasslands results in more homogenous soil microtopographic relief. Changes in soil microtopographic relief were measured prior to and following a total of five fires at three semiarid grasslands within central New Mexico, United States. The fires included three cool-season prescribed fires, a warm-season prescribed fire, and a warm-season wildfire. Four of the five fires resulted in significantly lower soil microtopographic variation that persisted for up to 4 yr. The duration and magnitude of the soil leveling effect was lowest in the grassland with clay-rich soils, indicating a possible soil texture interaction. Although two grasslands had net soil loss following fires, no net erosion occurred at the third grassland, indicating that redistribution of soils can occur without net erosion. These results show that management with prescribed fire reduces biotic-driven variation in soil microtopographic relief in semiarid grasslands that may help limit the transition to shrubland ecosystems in this region.
    • Plains Prickly Pear Response to Fire: Effects of Fuel Load, Heat, Fire Weather, and Donor Site Soil

      Vermeire, Lance T.; Roth, Aaron D. (Society for Range Management, 2011-07-01)
      Plains prickly pear (Opuntia polyacantha Haw.) is common throughout the Great Plains and often becomes detrimental to agricultural production on noncultivated lands. We examined direct fire effects on plains prickly pear and mechanisms of tissue damage to facilitate development of fire prescriptions. Cladodes from clones on three soils (claypan, gravelly, silty) were subjected to fire with two weather conditions (moderate, severe) at four fuel loads (1 500, 3 000, 4 500, and 6 000 kg ha-1) and a nonburned control. Fire was simulated with field-collected grass, and heat was measured using thermocouples at the soil surface and 8 cm above. Plants were maintained in a greenhouse and monitored for cladode mortality or growth. Cactus response to fire was examined in a field experiment with four nonburned and four summer-burned 0.75-ha plots. Some plants from each treatment sprouted new cladodes. Donor site soil and fire weather effects were limited to mass of new sprouts as they interacted with fuel load. Fire under any condition reduced cactus mass and survival. Reduction in cactus mass increased from 42% with 1 500 kg ha-1 to 92% with fuel loads of 3 000 kg ha-1 or more. Fuel load, duration of heat, maximum temperature, and degree-seconds were each positively related to mortality, but duration of heat greater than 60 degreesC was the best predictor. Plant mortality was 15% in the field, but number of live cladodes was initially reduced 91%. After one year, number of live cladodes in burned plots was 43% of that in nonburned plots because burned plants sprouted more new cladodes than nonburned plants. Insect and browsing damage occurred on 83% of cladodes in burned plots and only 8% for nonburned plots. Lack of fire weather effects suggests prickly pear control can be achieved under broad fire prescriptions, given the amount of combustible fuel is adequate.
    • Aboveground Macroinvertebrate Diversity and Abundance in Sand Sagebrush Prairie Managed With the Use of Pyric Herbivory

      Doxon, Elizabeth D.; Davis, Craig A.; Fuhlendorf, Samel D.; Winter, Stephen L. (Society for Range Management, 2011-07-01)
      Through pyric herbivory (i.e., fire-induced grazing patterns), native grasslands were historically a spatially heterogeneous environment. It is hypothesized that the mosaic of habitats created by pyric herbivory supports a more diverse invertebrate community compared to modern range management. Patch-burn management, a pyric herbivory technique, is an application of prescribed fire and grazing whereby the timing and location of the burned and grazed patches is varied, creating a diversity of habitat conditions. Although disturbance in sandsage (Artemisia filifolium Torr.) prairie historically included fire and grazing, fire disturbance has been nearly eradicated from this ecosystem in western Oklahoma. We compared patch-burn management to traditional management (i.e., moderate grazing with no fire) in sandsage prairie to evaluate the impact of these two management regimes on aboveground invertebrates. We sampled invertebrates at 44 points in each of 3 mo (May, June, and July) with the use of Dietrick vacuum sampling. Diversity, total abundance, and abundance of seven invertebrate orders (Araneae, Diptera, Hemiptera, Homoptera, Hymenoptera, Lepidoptera, and Orthoptera) were similar between patch-burn and traditional pastures. When examined on a patch level, five invertebrate orders were also similar between their respective time since burn patch and the traditional patches. Araneae and Coleoptera abundance were higher in traditional patches, and Hemiptera abundance was higher in current-year burn patches. Our results suggest a heterogeneity-based management scheme based on pyric herbivory does not negatively impact the overall invertebrate community and may benefit a wider variety of invertebrates by providing areas of varying levels of disturbance. In comparison, homogeneous landscapes such as those created by traditional management may only benefit segments of the invertebrate community that have habitat associations with moderately disturbed or undisturbed areas. Therefore, a disturbance regime involving the interaction of fire and grazing may be valuable for maintaining biodiversity and productivity within sandsage prairie ecosystems.
    • Absence of a Grass/Fire Cycle in a Semiarid Grassland: Response to Prescribed Fire and Grazing

      McDonald, Christopher J.; McPherson, Guy R. (Society for Range Management, 2011-07-01)
      Many nonnative invasive grasses alter fire regimes to their own benefit and the detriment of native organisms. In southern Arizona the nonnative Lehmann lovegrass (Eragrostis lehmanniana Nees) dominates many semiarid grasslands where native grasses were abundant. Managers are wary of using prescribed fire in this fire-prone community partly due to the perceived effects of a grass/fire cycle. However, examples of the grass/fire cycle originate in ecosystems where native plants are less fire-tolerant than grasses and the invasive plant does not mimic the physiognomy of the native community. We investigate the effects of prescribed fire and livestock grazing on a semiarid grassland community dominated by a nonnative invasive grass. Lehmann lovegrass does not appear to alter the fire regime of semiarid grasslands to the detriment of native plants. Prescribed fire reduced the abundance of Lehmann lovegrass for 1 to 2 yr while increasing abundance of native grasses, herbaceous dicotyledons and fall richness, and diversity. Effects of livestock grazing were less transformative than the effects of fire in this long-grazed area, but grazing negatively affected native plants as did the combination of prescribed fire and livestock grazing. Although Lehmann lovegrass produces more fuel than native plants, fire frequency in semiarid grasslands appears to be limited by the paucity of above-average precipitation, which constrains high fuel loads. In addition, many native grasses tolerate high temperatures produced by Lehmann lovegrass fires. Consistent with previous research, fire does not promote the spread of Lehmann lovegrass, and more importantly human alteration of the fire regime is greater than the nominal effects of Lehmann lovegrass introduction on the fire regime.
    • Vegetation Response to a One-Time Spent Drilling Mud Application to Semiarid, Mixed-Grass Prairie

      Zvomuya, Francis; Larney, Francis J.; Willms, Walter D.; Beck, Ryan K.; Olson, Andrew F. (Society for Range Management, 2011-07-01)
      Landspraying while drilling (LWD) is an approved disposal method for water-based drilling mud (WBM) systems in western Canada. The mud is applied either on cultivated land, where it is incorporated by cultivation, or on vegetated land where it is not incorporated. This study examined the effects of summer WBM application (0, 15, 20, 40, and 80 m3 ha-1) on native vegetation properties. Our results indicated that LWD increased bare ground but decreased lichen cover at the 80 m3 ha-1 rate relative to the untreated control. Nitrogen (N), sulfur (S), and magnesium (Mg) concentrations in aboveground plant tissue increased with increasing LWD rate in samples taken 45 d after WBM application, but these differences disappeared 1 yr after treatment. Increase in tissue concentration of phosphorus (P) with LWD rate, however, was only detected 3 yr after LWD. Nonetheless, these changes in tissue chemistry were not associated with significant changes in biomass yield or species composition. Overall, our results suggest that single WBM applications at rates (< 20 m3 ha-1) commonly used in western Canada, if properly managed, are unlikely to adversely affect native prairie vegetation.
    • Is Hand Plucking an Accurate Method of Estimating Bite Mass and Instantaneous Intake of Grazing Herbivores?

      Bonnet, Oliver; Hagenah, Nicole; Hebbelmann, Lisa; Meuret, Michel; Shrader, Adrian M. (Society for Range Management, 2011-07-01)
      Instantaneous intake is central to the understanding of large herbivore foraging strategies and rangeland ecology. Unfortunately, its measurement under field conditions remains challenging because of the difficulty of estimating bite mass. The hand plucking method provides a simple, noninvasive method of estimating bite masses and thus instantaneous intake of grazing herbivores. However, many authors questioned its accuracy and interobserver repeatability. In this study, we tested the accuracy and the repeatability of the hand plucking method using four observers and two herbivore species (i.e., cattle and goats). We compared hand plucked bite mass estimates to actual bite mass of bites taken by the herbivores on natural patches of grass. Training of the observers was fundamental to obtaining accurate bite mass measurements. The mean daily accuracy of the observers’ bite mass estimates increased from 60-80% to 80-94% within 5 d. After training, the relationship between bite mass estimates and actual bite mass was linear and not significantly different from a Y = X relationship. This means that individual bite mass estimates were centered on the real values and thus positive and negative errors canceled each other when combined. As a result, estimates of cumulative intake over about 10 feeding stations had accuracies of over 95%. Furthermore, neither the observer identity nor the herbivore species affected the accuracy of the measurements. The categorization of bites into different size categories proved to be essential in achieving accurate measurements. When observers are trained, hand plucking is a reliable and accurate method of estimating bites mass and instantaneous intake of grazing herbivores. This has important implications for rangeland research and management, as hand plucking is often the only practicable method available for estimating instantaneous intake of free-ranging herbivores.
    • Immature Seedling Growth of Two North American Native Perennial Bunchgrasses and the Invasive Grass Bromus tectorum

      Ray-Mukherjee, Jayanti; Jones, Thomas A.; Adler, Peter B.; Monaco, Thomas A. (Society for Range Management, 2011-07-01)
      Pseudoroegneria spicata (Pursh) A. Löve and Elymus wawawaiensis J. Carlson Barkworth are two native perennial grasses widely used for restoration in the Intermountain West. However, the rapid establishment and spread of Bromus tectorum L., an invasive annual grass, has led to a decline in the abundance of native perennial grasses. Proliferation of B. tectorum has been attributed to its early germination, superior cold-temperature growth, profuse root production, and high specific leaf area (SLA). To enhance restoration success, we compared B. tectorum to commercially available plant materials of two perennial rangeland bunchgrasses, P. spicata (cv. Whitmar, cv. Goldar, and Anatone Germplasm) and E. wawawaiensis (cv. Secar), for germination, seedling morphological traits, and growth rates at the immature seedling stage. We monitored germination and immature seedling growth in a growth chamber in two separate experiments, one under low (5/10 degreesC) and the other under high (15/20 degreesC) day/night temperatures. Compared to the average of the two perennials, B. tectorum was 93% (77%) greater at high (and low) temperature for root:shoot length ratio, but only 14% (14%) greater for root:shoot biomass ratio and 12% (19%) lower for SLA. This suggests that B. tectorum’s substantial investment in surface area of roots, rather than in shoot length, root biomass, or leaf area, may be responsible for the annual’s success at the early seedling stage. Compared to E. wawawaiensis, P. spicata averaged 65% (41%) higher shoot biomass, 39% (88%) higher root biomass, and 70% (10%) higher absolute growth rate, but 25% (15%) lower SLA and 15% (36%) lower specific root length (SRL) at high (and low) temperatures, respectively. Although P. spicata’s greater productivity may initially make for better seedling establishment than E. wawawaiensis, it may also prove disadvantageous in competitive or highly resource-limited environments where high SLA or SRL could be an advantage.
    • Decreasing Precipitation Variability Does Not Elicit Major Aboveground Biomass or Plant Diversity Responses in a Mesic Rangeland

      Derner, Justin D.; Hickman, Karen R.; Polley, Wayne (Society for Range Management, 2011-07-01)
      Inter- (between years) and intra- (within year) annual variability of precipitation are high on rangelands. We used replicated rainout shelters in a southern tallgrass prairie ecosystem to decrease precipitation variability for 3 yr (1999-2001). We removed interannual variability in total precipitation plus either 1) interannual variability in the seasonal distribution of precipitation (seasonal distribution) or 2) all additional variability in precipitation, including within-year differences in precipitation (even distribution). Our objective was to determine if decreasing variability in precipitation elicits aboveground biomass and plant diversity responses. Aboveground biomass was harvested in June (peak biomass) and December (end of growing season). Plant species diversity, richness, and evenness were determined each June. Reducing precipitation variability had limited effects on total aboveground biomass, grass and forb biomass, and biomass of key species across the 3 yr of investigation. Species richness, species diversity, species evenness, and functional group richness and diversity all were similar across the precipitation treatments across years. Total aboveground biomass and biomass of the dominant C4 perennial grasses little bluestem (Schizachyrium scoparium) and Indiangrass (Sorghastrum nutans) generally were not responsive to the precipitation treatments. However, one species-specific response did occur with the annual forb firewheel (Gaillardia pulchella Foug.) displaying consistent increases in biomass in the seasonal distribution precipitation treatment across all 3 yr. This suggests that increased predictability of precipitation at a given stage of this species’s growth can elicit changes in productivity of a single species that are not manifest at the community level due to constraints of the dominant species. These findings indicate that the southern tallgrass prairie ecosystem is adaptable to changes in precipitation to result in relatively stable production that facilitates simpler predictions in response to altered precipitation regimes.
    • Comparing Ecological Site Descriptions to Habitat Characteristics Influencing Greater Sage-Grouse Nest Site Occurrence and Success

      Doherty, Kevin E.; Beck, Jeffrey L.; Naugle, David E. (Society for Range Management, 2011-07-01)
      We used 119 greater sage-grouse (Centrocercus urophasianus) nests located in the Powder River Basin of northeastern Wyoming during 2004-2007 to assess the ability of US Department of Agriculture-Natural Resource Conservation Service (USDA-NRCS) ecological site descriptions (ESDs) to predict nest occurrence and success. We used nesting data from a regional study in the Powder River Basin that documented effects of local and landscape scale habitat characteristics on nest occurrence and success. We compared ESD metrics to these predictive local and landscape habitat variables where NRCS ESD field surveys overlapped our regional nest data set. We specifically asked three questions: 1) Are ESDs useful in predicting sage-grouse nest site occurrence and success as a univariate explanatory variable? 2) Can ESD information refine predictions of local scale nest site occurrence and success models? 3) Can ESD information refine landscape scale nest site occurrence models by serving as a surrogate for local scale information that cannot be mapped in a geographic information system (GIS)? Our results demonstrated that all models using ESD information were within +/- 2 Akaike’s Information Criterion points of a constant only model (i.e., null model) for local-scale data, or a baseline model where local- and landscape-scale habitat metrics were held constant while allowing ESD models to compete for remaining variation. No ESD metrics were statistically significant at the 95% level (P < 0.05), although some were significant at the 80-90% level (P = 0.09-0.14). Our study does not support the use of ESDs to predict habitat use or base sage-grouse management decisions in the Powder River Basin, but in some instances the refutation was weak. Local and landscape based habitat metrics showed high discrimination between null models with highly significant relationships on the subset data.
    • Public Perceptions of Sagebrush Ecosystem Management in the Great Basin

      Shindler, Bruce; Gordon, Ryan; Brunson, Mark W.; Olsen, Christine (Society for Range Management, 2011-07-01)
      Intact sagebrush communities in the Great Basin are rapidly disappearing because of invasion of nonnative plants, large wildfires, and encroachment of pinyon and juniper woodlands. Land management options, including the use of prescribed fire, grazing, herbicides, or mechanical treatments, can reduce the potential for wildfire and restore plant communities. Public acceptance of management actions, and trust in agencies to carry out those actions, is a critical component of developing and implementing successful long-term land management plans. This study examines citizens’ opinions and perceptions about rangeland management in the Great Basin. In fall 2006 we conducted a mail survey of randomly selected households in three urban and three rural regions of the Great Basin, receiving 1 345 valid responses for a 45% response rate. Overall, respondents perceived that the environment is moderately healthy; however, they do recognize threats to sagebrush ecosystems. Public acceptance is relatively high for the use of prescribed fire, grazing, felling woodland trees, and mowing shrubs, but low for herbicide treatment and chaining. Although respondents indicated high levels of acceptance for some management actions, they expressed relatively low levels of trust in land management agencies to implement these actions.
    • Origin, Persistence, and Resolution of the Rotational Grazing Debate: Integrating Human Dimensions Into Rangeland Research

      Briske, D. D.; Sayre, Nathan F.; Huntsinger, L.; Fernandez-Giminez, M.; Budd, B.; Derner, J. D. (Society for Range Management, 2011-07-01)
      The debate regarding the benefits of rotational grazing has eluded resolution within the US rangeland profession for more than 60 yr. This forum examines the origin of the debate and the major reasons for its persistence in an attempt to identify common ground for resolution, and to search for meaningful lessons from this central chapter in the history of the US rangeland profession. Rotational grazing was a component of the institutional and scientific response to severe rangeland degradation at the turn of the 20th century, and it has since become the professional norm for grazing management. Managers have found that rotational grazing systems can work for diverse management purposes, but scientific experiments have demonstrated that they do not necessarily work for specific ecological purposes. These interpretations appear contradictory, but we contend that they can be reconciled by evaluation within the context of complex adaptive systems in which human variables such as goal setting, experiential knowledge, and decision making are given equal importance to biophysical variables. The scientific evidence refuting the ecological benefits of rotational grazing is robust, but also narrowly focused, because it derives from experiments that intentionally excluded these human variables. Consequently, the profession has attempted to answer a broad, complex question—whether or not managers should adopt rotational grazing—with necessarily narrow experimental research focused exclusively on ecological processes. The rotational grazing debate persists because the rangeland profession has not yet developed a management and research framework capable of incorporating both the social and biophysical components of complex adaptive systems. We recommend moving beyond the debate over whether or not rotational grazing works by focusing on adaptive management and the integration of experiential and experimental, as well as social and biophysical, knowledge to provide a more comprehensive framework for the management of rangeland systems.