The purpose of this paper is to recommend a framework and methodology for incorporating hydrologic data and ecohydrologic relationships in Ecological Site Descriptions (ESDs) and thereby enhance the utility of ESDs for assessing rangelands and guiding resilience-based management strategies. Resilience-based strategies assess and manage ecological state dynamics that affect state vulnerability and, therefore, provide opportunities to adapt management. Many rangelands are spatially heterogeneous or sparsely vegetated where the vegetation structure strongly influences infiltration and soil retention. Infiltration and soil retention further influence soil water recharge, nutrient availability, and overall plant productivity. These key ecohydrologic relationships govern the ecologie resilience of the various states and community phases on many rangeland ecological sites (ESs) and are strongly affected by management practices, land use, and disturbances. However, ecohydrologic data and relationships are often missing in ESDs and state-and-transition models (STMs). To address this void, we used literature to determine the data required for inclusion of key ecohydrologic feedbacks into ESDs, developed a framework and methodology for data integration within the current ESD structure, and applied the framework to a select ES for demonstrative purposes. We also evaluated the utility of the Rangeland Hydrology and Erosion Model (RHEM) for assessment and enhancement of ESDs based in part on hydrologic function. We present the framework as a broadly applicable methodology for integrating ecohydrologic relationships and feedbacks into ESDs and resilience-based management strategies. Our proposed framework increases the utility of ESDs to assess rangelands, target conservation and restoration practices, and predict ecosystem responses to management. The integration of RHEM technology and our suggested framework on ecohydrologic relations expands the ecological foundation of the overall ESD concept for rangeland management and is well aligned with resilience-based, adaptive management of US rangelands. The proposed enhancement of ESDs will improve communication between private land owners and resource managers and researchers across multiple disciplines in the field of rangeland management.

Pyric-herbivory is the spatial and temporal interaction of fire and grazing on area resources that results in site selection by animals on recently burned areas. Pyric-herbivory promotes heterogeneity by increasing bare ground on some patches and litter and aboveground biomass on other patches. The influences of this heterogeneity on hydrological properties and sediment transport are not well documented. We monitored the pattern of cattle occupancy on annually burned and patch burned pastures under moderate stocking rates of steers in the Tallgrass Prairie Preserve and quantified surface runoff and sediment transport for simulated rainfall of 10-year return storm intensity applied to different phases of the fire-grazing interaction in 2011 and 2012. Results showed that patch burn altered grazing distribution with cattle spending 70% of their time within the most recently burned areas. Our rainfall simulation results showed the high-intensity grazing following a spring fire did not have a prolonged, ecologically meaningful detrimental impact on hydrological properties of the burned patch in comparison with annually burned grazing pasture. Instead, the increased spatial and temporal heterogeneity of hydraulic properties could potentially enhance resource conservation through runoff and runon interactions within the patch-burned pasture. Further study focusing on quantifying pyric-herbivory effects on runoff and sediment transport at watershed scale will provide needed insights for managing tallgrass prairie for improving ecosystem services.

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.

In native campos of Uruguay, overseeding legumes coupled with phosphorus (P) fertilization is a technology used to increase animal production. Short-term improvements in both forage productivity and quality are repeatedly reported. However, some evidence suggests that this management may at times lead to the collapse of the native community and invasions by exotic species. Indeed, it is yet unclear to what extent overseeding legumes into native grasslands affects its long-term integrity. This study uses data from a long-term experiment to assess whether increased P fertilizer rates—typically used to encourage legume establishment and growth—are associated with reduced species diversity. In 1996 a grazed native grassland in eastern Uruguay was either left untouched (control) or overseeded with a mix of Trifolium repens and Lotus corniculatus and then fertilized at either a moderate or high rate of P (197 or 394 kg · ha^-1 over 13 years, respectively). The three treatments were arranged in a randomized block design with four replicates of 2 hectares each. In 2005 the experiment was exhaustively sampled: 11 georeferenced sampling points per replicate, each encompassing∼20 m². Extractable P was measured in the 0—5- and 5—15-cm soil layers. In 2009, species presence and cover were measured at the same points. Across treatments, wherever legumes were introduced, extractable soil P was negatively related to species richness and diversity (P < 0.01) and native grass cover was reduced. This effect became asymptotic once soil P exceeded 27 and 36 mg · kg^-1 of P (0–5 cm), respectively. Therefore the documented reduction in species richness and diversity suggests a trade-off between increased pasture production and decreased vegetation stability may be operating in response to P fertilization of overseeded grasslands. The underlying ecophysiological mechanisms, as well as grazing management options to mitigate species diversity decline, should be further studied.

Managing the risk of wildfires is a growing concern in the western United States. Targeted grazing, or managing livestock grazing to achieve specific vegetation goals, is one possible tool to treat fuels, but few studies have evaluated its efficacy. The goal of this study was to test the effect of targeted grazing on herbaceous fuel loads and fire behavior by 1) implementing targeted grazing in a field experiment and 2) using a fire model (BehavePlus) to evaluate changes in fire behavior resulting from treatments. We applied targeted cattle grazing using low-stress herding and strategic placement of low-moisture block supplement on rugged rangelands in southwestern Arizona using a herd of 58 Red Angus cows and two bulls. Six of the cows were initially fitted with global positioning system collars. We tested two grazing treatments: 1) herding and supplement versus 2) no herding and no supplement on two pairs of study sites and replicated this for 2 years. Herding and supplement affected both the distribution of cattle and herbaceous fuel loads. Despite light utilization (26%) in treated sites, the BehavePlus fire model predicted that herding and supplement reduced fire rate of spread by more than 60% in grass communities and by more than 50% in grass/shrub communities. Fuel treatments dropped flame lengths below a 1.2-m critical threshold under the moderate fuel moisture scenario in grass communities and below a 2.4-m critical threshold in grass/shrub communities under both moderate and extreme fuel moisture scenarios. These results suggest that targeted grazing could reduce the potential cost of fighting fires in conditions similar to this study site. However, implementing this type of treatment on other sites will require careful calibration of animal numbers, supplement amounts, and length of herding periods relative to the specific context and goals.

Plant invasions are a threat to rangelands in California. Understanding how seeds of invasive plants are dispersed is critical to developing sound management plans. Domestic livestock can transport seeds long distances by ingesting and passing seeds in dung (endozoochory) or by the attachment of seeds to skin and fur (epizoochory). Our objective was to characterize the role of cattle as seed dispersers of both invasive and noninvasive species via endozoochory and epizoochory in a Sierra foothills rangeland. To quantify endozoochory, we sampled dung from two dry-season grazing periods and evaluated seed content by growing dung for 3 months in a greenhouse. To quantify epizoochory, we collected seeds directly from the fur of 40 cattle. We categorized the invasion status and functional groups of all species found and quantified landscape-scale vegetation composition in order to determine whether dispersal mode was associated with functional group, invasion status, or vegetation composition. Finally, we evaluated the potential for the noxious weed medusahead (Taeniatherum caput-medusae [L.] Nevski) to travel long distances on cattle fur using a detachment experiment with a model cow. We found that forbs were more likely to be dispersed by endozoochory, and invasive species were more likely to be dispersed by epizoochory. Medusahead was dispersed exclusively by epizoochory and was able to travel up to 160 m on a model cow. Our results suggest that cattle may be an important dispersal vector for both invasive and noninvasive plants.

We investigated the hypothesis that not only forage allowance but also sward structure affects daily forage intake by beef heifers on natural grasslands of the Pampa Biome (southern Brazil). We used data from a long-term experiment, which has been managed by forage allowance levels since 1986. The objective was to investigate sward management targets that maximize daily forage intake. During January and December 2009, we evaluated the effect of forage allowance on forage mass, sward height and tussock frequency, and its consequences on dry matter intake (DMI). The experiment was arranged in a randomized complete block design with two replicates. Treatment was level of daily forage allowance (4, 8, 12, and 16 kg dry matter [DM] per 100 kg of animal body weight [BW]). Data were analyzed using regression, principal component analysis, and descriptive analyses from three-dimensional contour graphs with the data of sward structure, DMI, and DMI rate. Results demonstrated that DMI was positively correlated to forage allowance. However, higher levels of forage allowance can cause lower intake rates of forage and nutrients. We concluded that sward targets which promoted higher DMI and DMI rate were: daily forage allowance of ∼ 12 kg of dry matter per 100 kg of the animal's body weight, forage mass between 1 800 and 2 300 kg DM·ha^-1, sward height between 11.5 and 13.4 cm, and tussock frequency lower than 30% of occurrence in the pastures. Within these targets, a high intake of nutrients was obtained, indicating the potential use of sward structure as a tool for managing natural grasslands in order to promote high intake of forage and nutrients by cattle.

Grazing facilitates foraging opportunities for brown-headed cowbirds (Molothrus ater), an obligate brood parasite. Cowbirds can reduce productivity of their hosts, causing some host species to decline in abundance. Thus grazing indirectly influences productivity of some songbirds. The black-capped vireo (Vireo atricapilla) is an endangered songbird with most of its breeding range occurring in areas of ungulate grazing. A contributing factor to its endangered status is brown-headed cowbird parasitism. We monitored 382 black-capped vireo nests from 2012–2013 in Real, Kerr, Bandera, and Edwards Counties, Texas. We investigated how enclosed ungulate (characterized by the presence of enclosed ungulates) and wild ungulate—only (characterized by the absence of enclosed ungulates) systems influenced brood parasitism. We also examined how distance to water (distance from nest to nearest ungulate water source), nest concealment, and grassland in the landscape (proportion of grassland within 3 km of a nest) related to parasitism. Overall parasitism frequency was 30% (n = 166) in 2012 and 31% (n = 216) in 2013, moderate compared with other research, but above a proposed 30% threshold of concern. Grassland in the landscape was not important in predicting brood parasitism in wild ungulate—only grazing systems, but it was important in predicting brood parasitism in enclosed ungulate systems. In enclosed ungulate systems, there was low probability of brood parasitism with a small amount of grassland in the landscape and high probability of parasitism with a large amount of grassland in the landscape. Nest concealment and distance to water were not good predictors of brood parasitism.

Managers of rangeland ecosystems require methods to track the condition of natural resources over large areas and long periods of time as they confront climate change and land use intensification. We demonstrate how rangeland monitoring results can be synthesized using ecological site concepts to understand how climate, site factors, and management actions affect long-term vegetation dynamics at the landscape-scale. Forty-six years of rangeland monitoring conducted by the Bureau of Land Management (BLM) on the Colorado Plateau reveals variable responses of plant species cover to cool-season precipitation, land type (ecological site groups), and grazing intensity. Dominant C₃ perennial grasses (Achnatherum hymenoides, Hesperostipa comata), which are essential to support wildlife and livestock on the Colorado Plateau, had responses to cool-season precipitation that were at least twice as large as the dominant C₄ perennial grass (Pleuraphis jamesii) and woody vegetation. However, these C₃ perennial grass responses to precipitation were reduced by nearly one-third on grassland ecological sites with fine- rather than coarse-textured soils, and there were no detectable C₃ perennial grass responses to precipitation on ecological sites dominated by a dense-growing shrub, Coleogyne ramosissima. Heavy grazing intensity further reduced the responses of C₃ perennial grasses to cool-season precipitation on ecological sites with coarse-textured soils and surprisingly reduced the responses of shrubs as well. By using ecological site groups to assess rangeland condition, we were able to improve our understanding of the long-term relationships between vegetation change and climate, land use, and site characteristics, which has important implications for developing landscape-scale monitoring strategies.

Current climate change (e.g., temperature and precipitation variations) profoundly influences terrestrial vegetation growth and production, ecosystem respiration, and nutrient circulation. Grasslands are sensitive to climate change, and the carbon sequestration ability is closely related to water availability. However, how the terrestrial water budget influences regional carbon sequestration by the grassland ecosystem is still unclear. In this study, we modified a terrestrial biogeochemical model to investigate net ecosystem productivity (NEP) of Chinese grasslands under different aridity index (AI) levels from 1982 to 2008. The results showed that Chinese grasslands acted as a carbon sink of 33.7 TgC. yr^-1, with a clear decrease in the spatial distribution from the humid end (near-forest) to the arid end (near-desert). During these 27 years, gross primary productivity (GPP) and net primary productivity (NPP) significantly increased with regional warming over the entire range of the AI, but no significant tendency was found for NEP. Meanwhile, only NPP in the arid zone (AR) and the semiarid zone (SAR) were significantly correlated with mean annual precipitation (MAP), and no significant correlation was found between heterotrophic respiration (R_h and MAP; NPP and R_h were both positively correlated with mean annual temperature (MAT) in all AI zones except for NPP in AR; no significant correlation between NEP and MAP or MAT was found. These results revealed that the grasslands with different AI levels keep different response patterns to temperature and precipitation variations. On the basis of these results, we predicted that the gap of carbon sequestration ability between humid and arid grassland will expand. The total carbon sink in Chinese grasslands will continue to fluctuate, but there is a danger that it might shrink in the future because of a combination of climatic and human factors, although CO₂ fertilization and N deposition might partly mitigate this reduction.