Millions of hectares of sagebrush/bunchgrass rangeland in the western United States are undergoing type conversion to systems dominated by introduced annual grasses that proliferate after wildfire. Postfire rehabilitation and restoration are problematic in these complex systems, but restoration difficulties are exacerbated by high annual and seasonal variability in precipitation and persistent drought. Successful restoration of compositional, structural, and functional diversity in these weather-limited systems may require relatively long-term, iterative management that incorporates flexibility in the definition of the aspirational/goal state. Restoration planning should also explicitly accommodate a lack of predictability of individual-year management results and expectations of only partial success of individual-year management treatments. This planning environment may require rapid assessment and contingency planning in the short term but also long-term persistence to overcome expected failures and setbacks. New methodologies are needed to increase biodiversity without damaging previously established plants, and new metrics need to be developed to monitor successional trajectories between initial and multiple-potential goal states.

Rangeland seeding practices in the Intermountain western United States are predominantly implemented in the year immediately following wildfire for the purposes of Emergency Stabilization and Rehabilitation (ESR). This necessarily links restoration and rehabilitation outcomes to the probability of a single year providing sufficiently favorable microclimatic conditions for desirable plant establishment. Field research studies in rangeland restoration are also typically of limited duration, and published results may not represent the full spectrumof conditions likely to be experienced at a given site. We propose that location-specific and temporal weather analysis may enhance the interpretation of historical planting data, support expanded inferences from short-term field studies, and facilitate meta-analysis of diverse field studies in rangeland restoration. We describe access and use of new databases and tools that can be used to characterize and rank weather and soil-microclimatic variables and suggest some standard graphs and weather metrics to establish a longer-term perspective for the interpretation of rangeland restoration outcomes. Tools of this type may also be useful in the interpretation of a wide range of agricultural and natural resource applications that are driven by similar weather inputs, particularly in arid and semiarid systems that exhibit high annual and seasonal variability in precipitation and temperature.

Management impacts and natural events can produce ecosystem state changes that are difficult to reverse. In such cases, a detailed understanding of drivers, thresholds, and feedback mechanisms are needed to design restoration interventions. The Caldenal ecoregion in central Argentina has undergone widespread state change, and restoration is urgently needed, but as yet there has been no knowledge synthesis to support restoration actions. In this paper, we provide evidence-based guidelines for ecological restoration of the Caldenal forest derived from a general to local conceptual understanding of ecosystem dynamics. We develop a Caldenal forest state transition model based on a generalized fire-mediated savanna-woodland transition model. The generalized model depicts global similarities in fire-grass feedback loops as a primary factor controlling savanna to woodland transition (thicketization) in semiarid savannas around the world. An open forest is considered to be the reference state of the Caldenal that developed under a historical regime of frequent low-intensity fire. The introduction of large livestock herds in the region disrupted the positive fire-grass feedback loop and increased dispersal and recruitment of Prosopis caldenia, creating conditions for thicketization of the forest. Controlled, low-intensity fire can be used to build the resilience of an open forest state. Restoring open forest states from woodland states requires a large-scale selective thinning and pruning operation. Long-term restoration requires breaking the positive livestock-thicketization-high-intensity fire feedback and reestablishing the positive grass-low intensity fire feedback to ensure the persistence of a restored open forest state.

Past seedings of crested wheatgrass (Agropyron cristatum [L.] Gaertn. and A. desertorum [Fisch. ex Link] Schult.) have the potential to persist as stable, near-monospecific stands, thereby necessitating active intervention to initiate greater species diversity and structural complexity of vegetation. However, the success of suppression treatments and native species seedings is limited by rapid recovery of crested wheatgrass and the influx of exotic annual weeds associated with herbicidal control and mechanical soil disturbances. We designed a long-term study to evaluate the efficacy of low-disturbance herbicide and seed-reduction treatments applied together or alone and either once or twice before seeding native species. Consecutive herbicide applications reduced crested wheatgrass density for up to 6-7 yr depending on study site, but seed removal did not reduce crested wheatgrass abundance; however, in some cases combining herbicide application with seed removal significantly increased densities of seeded species relative to herbicide alone, especially for the site with a more northern aspect. Although our low-disturbance treatments avoided the pitfalls of secondary exotic weed influx, we conclude that crested wheatgrass suppression must reduce established density to values much lower than 4–7 plants/m², a range that has not been obtained by ours or any previous study, in order to diminish its competitive influence on seed native species. In addition, our results indicated that site differences in environmental stress and land-use legacies exacerbate the well-recognized limitations of native species establishment and persistence in the Great Basin region.

Restoring arid regions degraded by invasive annual grasses to native perennial grasses is a critical conservation goal. Targeting site availability, species availability, and species performance is a key strategy for reducing invasive annual grass cover while simultaneously increasing the abundance of seeded native perennial grasses. However, the potential for establishing successful seedings is still highly variable in rangeland ecosystems, likely because of variable year-to-year weather. In this study, we evaluated the independent and combined inputs of tilling, burning, applying imazapic herbicide, and varying seeding rates on existing species and seeded native perennial grass performance from 2008 to 2012 in a southwestern Idaho rangeland ecosystem. Wefound that combining tilling, fire, and herbicides produced the lowest annual grass cover. The combination of fire and herbicides yielded the highest seeded species density in the hydrologic year (HY) (October-September) 2010, especially at higher than minimum recommended seeding rates. Although the independent and combined effects of fire and herbicides directly affected the growth of resident species, they failed to affect seeded species cover except in HY 2010, when weather was favorable for seedling growth. Specifically, low winter temperature variability (few freeze-thaw cycles) followed by high growing season precipitation in HY 2010 yielded 14× more seeded perennial grasses than any other seeding year, even though total annual precipitation amounts did not greatly vary between 2009 and 2012. Collectively, these findings suggest that tilling, applying prescribed fire, and herbicides before seeding at least 5× the minimum recommended seeding rate should directly reduce resident annual grass abundance and likely yield high densities of seeded species in annual grass-dominated ecosystems, but only during years of stable winter conditions followed by wet springs.

Degradation of shrublands around the world from altered fire regimes, overutilization, and anthropogenic disturbance has resulted in a widespread need for shrub restoration. In western North America, reestablishment of mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana [Rydb.] Beetle) is needed to restore ecosystem services and function. Western juniper (Juniperus occidentalis ssp. occidentalis Hook) encroachment is a serious threat to mountain big sagebrush communities in the northern Great Basin and Columbia Plateau. Juniper trees can be controlled with fire; however, sagebrush recovery may be slow, especially if encroachment largely eliminated sagebrush before juniper control. Short-term studies have suggested that seeding mountain big sagebrush after juniper control may accelerate sagebrush recovery. Longer-term information is lacking on how sagebrush recovery progresses and if there are trade-offs with herbaceous vegetation. We compared seeding and not seeding mountain big sagebrush after juniper control (partial cutting followed with burning) in fully developed juniper woodlands (i.e., sagebrush had been largely excluded) at five sites, 7 and 8 yr after seeding. Sagebrush cover averaged - 30% in sagebrush seeded plots compared with - 1% in unseeded plots 8 yr after seeding, thus suggesting that sagebrush recovery may be slow without seeding after juniper control. Total herbaceous vegetation, perennial grass, and annual forb cover was less where sagebrush was seeded. Thus, there is a trade-off with herbaceous vegetation with seeding sagebrush. Our results suggest that seeding sagebrush after juniper control can accelerate the recovery of sagebrush habitat characteristics, which is important for sagebrush-associated wildlife. We suggest land manager and restoration practitioners consider seeding sagebrush and possibly other shrubs after controlling encroaching trees where residual shrubs are lacking after control.

Invasive plants are spreading throughout arid and semiarid rangelands of western North America. Long-lived perennial plants that can persist under harsh environmental conditions are needed to compete with invasive species. The objective of this study was to conduct a long-term evaluation of native and introduced grass species planted to suppress and prevent reinvasion of downy brome (Bromus tectorum L.), snakeweed (Gutierrezia sarothrae [Pursh] Britt. & Rusby), and annual forbs. Seeding treatments comprised three introduced grasses: crested wheatgrass (Agropyron cristatum [L.] Gaertner × A. desertorum [Fisch. Ex Link] Schultes), pubescent wheatgrass (Elytrigia intermedia spp. trichophorum [Host] Beauv.), and Russian wildrye (Psathyrostachys junceus [Fisch.] Nevski); a mix of these introduced grass species, three native grasses: bluebunch wheatgrass (Pseudoroegneria spicata [Pursh]), western wheatgrass (Pascopyrum smithii [Rybd.] A. Löve), and squirreltail (Elymus multisetus [J.G. Sm.] Jones); and a mix of these native grass species, or forage kochia (Bassia prostrata [L.] A.J. Scott). The treatments were seeded in October 2003. Frequency and biomass were measured in 2015 and 2017 in Howell, Utah and in 2015 and 2016 in Nephi, Utah. Crested wheatgrass persisted at both locations (> 62% frequency) along with the rhizomatous grass species, pubescent (> 65%) and western wheatgrasses (> 72%). Russian wildrye was still present at Howell (30%)with little remaining at Nephi (7%). Squirreltail frequency was 13% at Howell and 12% at Nephi. Bluebunch wheatgrass was no longer present at either location (< 1%). Forage kochia remained at Nephi (36%) with little remaining at Howell (4%). Downy brome was present at both locations and was suppressed relative to control plots, at Nephi, by crested wheatgrass and the introduced grass mix (< 9%). Downy brome was > 93% in all plots, at Howell, in 2017. In summary, crested, pubescent, and western wheatgrasses were able to persist over 12 yr at both locations.

Shrub encroachment into grasslands is a worldwide phenomenon with no signs of abating and numerous ecological consequences. In South Texas, honey mesquite (Prosopis glandulosa Torr.) and huisache (Vachellia farnesiana [L.] Wight & Arn.) are two shrubs encroaching into coastal prairies, reducing cover of the dominant native grass, gulf cordgrass (Spartina spartinae [Trin.]Merr. ex Hitchc.), and decreasing habitat for the endangered Aplomado Falcon (Falco femoralis), which requires grasslands or savannas for survival. To determine the best management approach for deterring shrub encroachment and restoring native grasslands, the US Fish and Wildlife Service used several shrub removal techniques within coastal prairies of the Bahía Grande Wetland Complex of the Laguna Atascosa National Wildlife Refuge, a core site for Aplomado Falcon reintroductions. Here, we assess native grass recovery over a 2-yr period in response to these shrub removal methods (mechanical plus prescribed fire and/or herbicide treatments) and degree of shrub encroachment before treatment. In general, areas with high levels of shrub encroachment before treatment had the highest amount of bare ground and lowest grass cover immediately following an initial mechanical treatment; this legacy effect persisted throughout the study irrespective of shrub removal treatment. Regardless of degree of shrub encroachment before treatment, grasses in areas treated with either mechanical or mechanical followed by herbicide methods recovered the slowest, likely due to residual woody material that hindered seed germination. Herbicide treatment following mechanical removal or mechanical removal plus fire effectively hindered shrub regrowth. Overall, mechanical treatment followed by prescribed fire and then herbicide application most effectively promoted grass recovery while hindering shrub regrowth. These findings suggest that grassland recovery following shrub encroachment into South Texas coastal prairies may be promoted through the application of shrub removal methods that combine mechanical, fire, and herbicide treatments.

To better match plant materials to ecological sites for the purpose of rangeland seedling establishment, we examined the relationship between seed size and growth and morphological traits in young seedlings of bluebunch wheatgrass (BBWG) (Pseudoroegneria spicata [Pursh.] Á. Löve), a perennial Triticeae bunchgrass native to the Intermountain West. Traits examined included onset of germination, seedling biomass traits, and seedling surfacearea traits. We grew seeds of nine BBWG populations that varied for seed size and were produced in a common environment under 2 contrasting d/n temperature regimes (20/15°C; 10/5°C). Lighter-seeded populations germinated and initiated shoots earlier. Heavier-seeded populations displayed high levels of biomass-related traits (e.g., shoot and root biomass and shoot length), while lighter-seeded populations displayed high levels of surface area-related traits (e.g., specific leaf area and specific root length [SRL]). Correlations between seed size and young-seedling traits were mostly similar under the two temperature regimes. However, root length-related traits showed more positive correlations with seed size under the low-temperature regime, which is more similar to actual field-emergence conditions during early spring. P-24, a light-seeded population, originated from the most arid site and exhibited the highest SRL at low temperature, while T-17t, a heavy-seeded population, originated from the most mesic site and exhibited moderate SRL. Three populations used for rangeland revegetation, “Whitmar,” “Goldar,” and Anatone Germplasm, all exhibited lowseed mass and high SRL. However, only Anatone displayed high root-to-shoot length ratio under both temperature regimes, perhaps explaining its wide and successful use in rangeland seedings.

Effective manipulations to prevent the spread of invasive species are needed. Downy brome (Bromus tectorumL.) is an annual invader that often expands after disturbances, compromising restoration of big sagebrush (Artemisia tridentata Nutt.) communities in western North America. This study examined the effects of two manipulations that may slow seed dispersal: soil microtopography (roughened with 50-cm relief or flat) and woody debris (0.024 m³·m^-2or none) on restoration of four disturbed mountain big sagebrush (A. tridentata Nutt. ssp. vaseyana) sites in Colorado. Treatments were crossed with seeding in a fully factorial experiment (n = 3). Microtopography and woody debris treatments were also crossed in a seed dispersal experiment using fluorescently marked downy brome seeds. In the restoration study, downy brome invaded two sites, one pervasively and one patchily. Seeding limited downy brome cover at both of these sites and also increased perennial grass and forb cover while limiting shrub cover. At the pervasively invaded site, the rough surface reduced unseeded plot downy brome cover from 13% to 3% by 5 yr post treatment. Woody debris increased shrub and perennial grass cover but had little effect on downy brome. In the seed dispersal experiment, the rough surface reduced downy brome mean dispersal distance twofold to threefold and 95% quantile distance threefold to sixfold. Woody debris slightly reduced downy brome dispersal only within rough surface plots. A rough surface may aid restoration by trapping downy brome seeds near the parent plant, limiting their spatial distribution, increasing intraspecific competition, and reducing propagule pressure. Designing landscapes to slowseed dispersal may help control invasives and promote establishment of seeded species.

Rangeland management strategies impact biodiversity, the quality and quantity of ecosystem services, and overall rangeland resiliency. Previous management strategies, coupled with climate change, have led to widespread invasion by Kentucky bluegrass (Poa pratensis; bluegrass) in the Northern Great Plains, United States. Bluegrass invasions are expected to have detrimental impacts on biodiversity conservation and ecosystem services provided by rangelands. Yet none have investigated how bluegrass invasions influence pollinator populations, which are a prominent conservation concern and provide ecosystem services. We measured the impact of bluegrass invasion on mixed-grass prairie forb and butterfly communities. Obligate grassland butterflies, those that rely on grasslands, decreased as bluegrass cover increased, including the threatened Hesperia dacotae. Conversely, the abundance of facultative grassland butterflies, those found in grasslands but not fully dependent on them for their life history, increased as bluegrass increased. Moreover, plant species diversity and flowering forb species richness decreased as bluegrass cover increased. Overall, bluegrass invasion led to butterfly and plant community simplification, signaling a loss of biodiversity and potentially ecosystem services. Our research is the first to quantify how grassland butterflies and the floral resources they depend on are negatively impacted by bluegrass invasion. Resource managers should adopt management strategies that reduce bluegrass cover and improve nectar and host resources for obligate grassland butterflies. Management choices that removed disturbance regimes inherent to the Northern Great Plains (i.e., fire and grazing) led to bluegrass dominance in the region. Therefore, restoring disturbance regimes may be one way to reduce bluegrass and benefit pollinator populations.

The fates of native bee communities in the Great Basin sagebrush steppe are linked with the susceptibilities of their floral hosts to increasingly frequent wildfires. Postfire survival and subsequent flowering of six prevalent perennial wildflowers representing five families were quantified across a range of realistic fire severities created using a calibrated propane burn barrel. Five burn prescriptions of varying intensity and duration were applied to cultivated rows of basalt milkvetch (Astragalus filipes Torr. ex A. Gray), Blue Mountain prairie clover (Dalea ornata Eaton & J. Wright), sulphur-flower buckwheat (Eriogonum umbellatum Torr.), fernleaf biscuitroot (Lomatium dissectum Nutt.), blue penstemon (Penstemon cyaneus Pennell), and gooseberryleaf globemallow (Sphaeralcea grossularifolia Hook. & Arn.). Overall differences in their fire sensitivitieswere maximal at peak fire severity, ranging from 80% survival (L. dissectum) to complete mortality (E. umbellatum and P. cyaneus). Although A. filipes survived well (85%), half of the 95 burn survivors then failed to flower the year after burning. The postfire fate of plant-pollinator interactions is a function of the bees' nesting habits, their floral host's sensitivity to a given burn intensity (both in terms of survival and flowering), and the reproductive interdependence of bee and floral host (taxonomic specialists vs. generalists).

The spatial distribution of different grassland types is important for effectively analyzing spatial patterns, obtaining key vegetation parameters using remote sensing (e.g., biomass, leaf area index, net primary production), and using and protecting grasslands. Existing classifications of grasslands by remote sensing are mostly divided according to the fractional vegetation cover or biomass, but classifications according to grassland types are scarce. In this study, we focused on the classification of different grassland types using remote sensing based on object-based image analysis (OBIA) with multitemporal images in combination with a 30-m digital elevation model (DEM) and the normalized difference vegetation index (NDVI). The grasslands were located in Hulunber, InnerMongolia, and an autonomous region of China. The support vector machine (SVM) and random forest (RF) machine learning classifiers were selected for the classification. The results revealed the following: 1) It is feasible to generally extract different grassland types on the basis of OBIA with multisource data; the overall classification accuracy and Kappa value exceeded 90% and 0.9, respectively, using the SVM and RF machine learning classifiers, and the classification accuracy of the different grassland types ranged from 61.64% to 98.71%; 2) Multitemporal images and auxiliary data (DEM and NDVI) improved the separability of different grassland types. The information in the growing season was conducive for distinguishing temperate meadow steppe from temperate steppe and was favorable for extracting lowland meadow and swamp in the nongrowing season. The DEM and NDVI also effectively reduced the number of image segmentation objects and improved the segmentation effects; 3) Spectral and textural features were more important than geometric features in this study. A few main variables played a major role in the classification, while a large number of variables had either no significant effect or a negative effect on the classification results when the optimal feature subset was determined. This study provides a scientific basis and reference for the classification of various grassland types by remote sensing, including the data selection, image segmentation, feature selection, classifier selection, and parameter settings.

The Three-River Headwaters (TRH) region is covered dominantly with alpine meadow, a large part of which is confronting severe degradation as a result of climate change and human-induced influences. The estimation of net primary productivity (NPP) is essential to provide support for scientific management of TRH grassland resources to prevent further degradation. The classification indices-based model (CIM) has been applied in the estimation of NPP and its response to global warming because of its simple structure and easily obtained indices. However, CIM is considered to estimate the potential NPP rather than the actual value. Thus, its application has been restricted. In this study, the normalized difference vegetation index (NDVI) was applied to modify the CIM. Then, CIM and modified CIM were compared with the other three models. The assessment of NPP estimates indicated that the modified CIM had a fair performance among the NPP models (R²= 0.42, RMSE = 178.08). All the NPP estimation models revealed that NPP increased from the northwest to the southeast. According to the modified CIM, the mean NPP of TRH grassland was 135.44 gC·m^-2·yr^-1and the total NPP was 3.22 × 10¹³gC·yr^-1. Among the classes of the grassland of TRH in the comprehensive and sequential classification system( CSCS), the frigid perhumid rain tundra and alpine meadow occupied most of the grassland NPP, which was 3.06× 10¹³gC·yr^-1. With the help of the NDVI, the modified CIM performed better than the CIM; however, there is still much room for the improvement of CIM in future research.

In order to promote the application of hyperspectral remote sensing in the quantification of grassland areas' physiological and biochemical parameters, based on the spectral characteristics of ground measurements, the dry AGB and multisensor satellite remote sensing data, including such methods as correlation analysis, scaling up, and regression analysis, were used to establish a multiscale remote sensing inversion model for the alpine grassland biomass. The feasibility and effectiveness of the modelwere verified by the remote sensing estimation of a time-space sequence biomass of a plateau grassland in northern Tibet. The results showed that, in the ground spectral characteristic parameters of the grassland's biomass, the original wave bands of 550, 680, 860, and 900 nm, as well as their combination form, had a good correlation with biomass. Also, the remote sensing biomass estimationmodel established on the basis of the two spectral characteristics (VI2 and Normalized Difference Vegetation Index [NDVI]) had a high inversion accuracy andwas easy to realize, with a fitting R2 of 0.869 and an F test value of 92.6. The biomass remote sensing estimate after scale transformation had a standard deviation of 53.9 kg/ha from the fitting model established by MODIS NDVI, and the estimation accuracy was 89%. Therefore, it displayed the ability to realize the estimation of large-scale and long-time sequence remote sensing biomass. The verification of themodel's accuracy, comparison of the existing research results of predecessors, and analysis of the regional development background demonstrated the effectiveness and feasibility of this method.

Wemapped yearly (2000–2016) estimates of annual grass percent cover for much of the sagebrush ecosystemof the western United States using remotely sensed, climate, and geophysical data in regression-tree models. Annual grasses senesce and cure by early summer and then become beds of fine fuel that easily ignite and spread fire through rangeland systems. Our annualmaps estimate the extent of these fuels and can serve as a tool to assist land managers and scientists in understanding the ecosystem's response toweather variations, disturbances, and management. Validating the time series of annual maps is important for determining the usefulness of the data. To validate these maps, we compare Bureau of Land Management Assessment Inventory and Monitoring (AIM) data to mapped estimates and use a leave-one-out spatial assessment technique that is effective for validating maps that cover broad geographical extents. We hypothesize that the time series of annual maps exhibits high spatiotemporal variability because precipitation is highly variable in arid and semiarid environments where sagebrush is native, and invasive annual grasses respond to precipitation. The remotely sensed data that help drive our regression-tree model effectively measures annual grasses' response to precipitation. The mean absolute error (MAE) rate varied depending on the validation data and technique used for comparison. The AIM plot data and our maps had substantial spatial incongruence, but despite this, the MAE rate for the assessment equaled 12.62%. The leave-one-out accuracy assessment had an MAE of 8.43%. We quantified bias, and bias was more substantial at higher percent cover. These annual maps can help management identify actions that may alleviate the current cycle of invasive grasses because it enables the assessment of the variability of annual grass-percent cover distribution through space and time, as part of dynamic systems rather than static systems.

Black-tailed prairie dogs (Cynomys ludovicianus) have high dietary overlap with livestock, which can cause forage-centric conflicts between agriculture and conservation. Research suggests prairie dogs can enhance forage quality, but trade-offs between quality and quantity throughout the growing season remain unclear, as well as the degree to which increased forage quality is caused by altered species composition versus altered plant physiology. To assess the effects of prairie dog herbivory on forage in a northern mixed-grass prairie, we collected samples on prairie dog colonies and at sites without prairie dogs during June, July, and August 2016 - 2017 for forage quality, and August 2015 - 2017 for herbaceous biomass. To isolate mechanisms affecting forage quality, we collected both composite samples of all herbaceous species and samples of western wheatgrass (Pascopyrum smithii [Rydb.] Á. Löve). Across years and plant sample types, crude protein, phosphorus, and fat were 12-44% greater and neutral detergent fiber was 6-10% lower on prairie dog colonies than at sites without prairie dogs. The effects of prairie dogs on forage quality persisted throughout the season for western wheatgrass samples (all treatment*time p-values ≥⃒ 0.4). Across years, aboveground herbaceous biomass did not differ significantly between prairie dog colonies and sites without prairie dogs (on-colony: 933 ± 156 kg/ha, off-colony: 982 ± 117 kg/ha). The effects of prairie dogs on herbaceous biomass were significantly influenced by spring precipitation. In years with dry springs, herbaceous biomass was lower on colonies than sites without prairie dogs and this pattern was reversed in years with wet springs. Our results demonstrate season-long enhanced forage quality on prairie dog colonies, indicating that multiple mechanisms are shaping forage quality in this system, including altered species composition, phenological growth stage, and soil condition. Across years, enhanced forage quality may help to offset reductions in forage quantity for agricultural producers.

Native colonial and large ungulate herbivores infrequently coexist on contemporary landscapes but frequently would have in the past, and understanding these interactions is important for conservation in working landscapes-those lands managed for biological and economic objectives. Although many factors contribute to grassland bird declines, consistent and long-term removal of native herbivores from western grasslands promotes homogenous landscapes that are now uniformly grazed by cattle (Bos taurus). This shift in grassland disturbance patterns limits habitat availability for specialized grassland species. We investigated vegetation and birdcommunity dynamics in pastures grazed by domestic cattle and a native colonial herbivore, the black-tailed prairie dog (Cynomys ludovicianus). The study occurred in the northern mixed-grass prairie of the United States on four experimental pastures stratified by the proportion of prairie dog occupancy to create an ecological gradient. Vegetation and bird surveys were conducted from 2012 to 2015 on and off prairie dog colonies. Vegetation and bird communities were not different along the experimental pasture gradient but did differ relative to location on versus off town. Prairie dogs induced changes in the plant community with midstatured grasses like side-oats grama (Bouteloua curtipendula) and green needlegrass (Nassella viridula) being associated with off-colony sites while on-colony sites were associated with disturbance-tolerant species such as fetid marigold (Dyssodia papposa). The bird community responded to changes in vegetation structure resulting from prairie dogs with grasshopper sparrows (Ammodramus savannarum) being more abundant off colonies in areas with greater vegetation structure, while bird species with more complex life histories, such as the upland sandpiper (Bartramia longicauda), were associated with both on-and off-prairie dog colonies. Our findings demonstrate the importance of maintaining spatial heterogeneity in working landscapes and show that native colonial herbivores can help achieve this in the presence of herbivory by domestic cattle.

Woody encroachment has influenced wildlife distributions and, thus, predator-prey dynamics, for many taxa in North American grasslands. In 2015 and 2016, we examined howvegetative characteristics influenced avian nest predator assemblages and nest predation rates in semiarid grasslands of south Texas, where encroachment of woody plant species is common. We monitored 253 nests of 17 bird species and deployed infrared cameras at 107 nest sites within four vegetation types at our study sites. We also used data from a concurrent, multispecies monitoring project within our study area to assess predator activity within these same vegetation types. We divided bird species into four nest types based on nest shape and size (i.e., small, medium, and large cup-shaped nests and exposed nests with little structure). We then used logistic regression to examine relationships between shrub cover, concealment, and distance to edge and the probability of nest success and predation by snakes. We observed a significant decrease in nest success of our medium-sized, cup-shaped nest type when shrub cover increased at the nest site, indicating small increases in shrub cover (≈10%) could have substantial impacts on birds using this nest type. Snakes were our primary predator at camera-monitored nests (59%), and snake activity increased by 6.7% with every 10% increase in shrub cover at the nest site. Mesomammalian and large mammalian predators were most active in vegetation types predominated by herbaceous cover, small mammals were most active in vegetation types predominated bywoody cover, and snake activitywas highly variable. Predator activity did not reflect predator identity at camera-monitored nests, suggesting that potential nest predator activity may not accurately reflect the risk of nest predation. Results of our study will help inform management of bird species using semiarid grasslands affected by woody encroachment and offer recommendations for improved nest success.

Soil carbon and sugars play key roles in carbon (C) cycling in grassland ecosystems. However, little is known about their changes in quantity and composition in degraded alpine meadows in the Tibetan plateau. We compared vegetation C density, soil organic carbon (SOC) density, and soil sugars in nondegraded (ND), degraded (DA; following artificial restoration), and extremely degraded (ED) grasslands and analyzed the relation among these parameters by redundancy analysis (RDA) and structural equation models (SEMs). Belowground biomass, soil microbial biomass C, soil microbial biomass nitrogen (N), belowground biomass C density, SOC density, and soil sugars were lower in DA and ED grasslands than in ND grasslands. In addition, the ratio of belowground biomass to aboveground biomass (BAR) decreased with an increase in degradation. The ratio of belowground biomass to aboveground biomass was identified as the main indirect driving force of ecosystem C density by affecting total vegetation C and SOC densities. Soil dissolved organic carbon (DOC), microbial biomass carbon (SMBC), neutral sugars (NS), and total nitrogen (TN) were identified as main direct driving forces. The ratio of belowground biomass to aboveground biomass altered DOC, SMBC, NS, and TN and, consequently, was the primary driving force for the alpine meadows' ecosystem C density. It was concluded that land management in alpine meadows should include practices that maintain a relatively high BAR in order to curb degradation and increase ecosystem C density.

Plant litter and livestock excreta are two important ways of carbon and nutrient input to soil in grassland grazing systems. Grazing livestock often deposit dung on plant litter, which may affect litter decomposition through a changing microenvironment. We assessed effects of yak dung on litter mixing effects on litter decomposition in a Tibetan alpine grassland. Six common species were selected, including low-quality litter species Kobresia capillifolia, Elymus nutans, and Ligularia virgaurea and high-quality litter species Anemone rivularis, Saussurea nigrescens, and Thermopsis lanceolata. Litter bags containing each species alone and all two-species combinations were allowed to decompose with and without experimental dung addition in the field. Mass loss of the leaf litter was measured after 6 and 12 mo. High-quality litter species had significantly greater mass loss than low-quality litter species. Dung significantly accelerated litter mass loss after both 6 and 12 mo for low-quality litter species, but only after 12 mo for high-quality litter species. Litter mixtures containing both high- and low-quality species showed positive nonadditive effects (NAEs) on mass loss after 6 mo but additive effects after 12 mo. Dung increased the strength of NAEs after 6 mo and shifted litter mixing effects from positive to negative NAEs after 12 mo. Our results support previous findings that litter mixing could produce NAEs on litter decomposition and that these NAEs could change with incubation time. Most importantly, we show that dung can modify NAEs, demonstrating that litter mixing effects are dependent on the microenvironment. Our findings also demonstrate that yak dung can influence soil processes by varying both single-species litter decomposition rates and litter interactions within mixtures. Furthermore, the results suggest yak dung is closely related to material and nutrient cycling, so we believe dung should remain and not be substantially removed from this grazing ecosystem.

Rangeland fire effects on flora, fauna, soils, and water have been studied widely. Fire effects information is limited on rangeland developments such as fencing. Fencing is an integral part of rangeland infrastructure and receives much attention when there is a wildfire or even discussion about conducting prescribed fires. Due to known fence age and fire history, we conducted a study on the Oklahoma State University Research Range located near Stillwater, Oklahoma. Five randomly selected individual metal T posts were sampled from a common fence line of known age and fire treatment. The T posts ranged from 4 to 35 yr since fence construction, with fire activity of 0, 1, 3, or 12 prescribed fires and 0, 1, or 2 wildfire occurrences. Each T post was tested in situ at 40 cm, 80 cm, and 120 cm above ground level for hardness and paint adhesion as set forth by American Society for Testing and Materials (ASTM) International standards for hot wroughtmetal fence posts. Our results found no differences in post hardness, with all posts tested being higher than the ASTM minimum standard of 83 Rockwell BHardness Scale. We also found that paint adhesion between burned and unburned T posts did not vary, with age of post being the only significant predictor variable for adhesion. Overall, our results provide evidence that T posts exposed to numerous fires and fire types did not suffer negative effects. This shows that concerns about wildfire and prescribed fires in grasslands having negative effects on metal T posts are unfounded.