Invasive plants have an increasing impact on the ecological and economic functions of natural systems. Cheatgrass (Bromus tectorum L.) is an invasive annual grass that is widely impactful throughout most of the western United States. Describing ecological and management thresholds in cheatgrass-invaded rangelands may help managers conserve native plant communities. The objective of this research was to determine if direct, predictable relationships exist between pretreatment vegetation conditions and posttreatment changes in perennial grass biomass following cheatgrass control. We sampled locations representing a gradient of cheatgrass-to–perennial grass ratios before and following application of two imazapic formulations—liquid imazapic with a water carrier and dry imazapic with sand/granular carrier—at field sites near Saratoga and Pinedale, Wyoming. We monitored vegetation responses 1 yr before treatment and 2 yr following treatment. We observed a general pattern that posttreatment increases in perennial grass biomass were greater where pretreatment relative cheatgrass canopy cover was higher, and magnitudes of increase varied according to site conditions. We tentatively suggest thresholds at ratios of pretreatment cheatgrass-to–perennial grass cover at 4:1, where perennial grass biomass increased following herbicide treatment and > 10:1, beyond which increases in perennial grasses were no longer observed. Such ratios provide a starting point for threshold identification in cheatgrass-invaded rangelands that may be transferrable across plant communities but need to be explored at a broader scale to adequately make management recommendations.

Arid steppes, with scattered vegetation, are commonly qualified as degraded ecosystems. Their natural vegetation cover is affected by both abiotic stresses and human activities and, therefore, suitable managements are needed for their sustainability. This study was carried out in the mountain rangeland chain of Matmata (southern dryland of Tunisia) during the springs of 2 rainy yr, 2019 and 2020. Our aims were to evaluate the impact of three grazing regimes (grazing exclusion [over 42 ys; 1978–2020]; seasonal [protected in spring and summer and grazed in autumn and winter, since the 1960s]; and continuous grazing [control; grazed over time]) on the cover of some plant life forms (Raunkiaer, Noy-Meir, and Grime types), under various conditions (sites, aspects, and elevations). To achieve this goal, the pseudoreplicated-nested design was applied, taking into account the site locations (grazing regimes), aspects (exposure to sunlight), and elevations. The cover of the retained plant life forms was measured using the quadrat point method. The main results showed that plant life forms are strongly affected by the grazing regime since the chamephytes (Ch_R), arido-active (AA_NM), and competitive stress-tolerant species (CS_G) are higher under seasonal grazing than control. All these species are qualified as less resistant to grazing. However, arido-passive (AP_NM), ruderal stress-tolerant (RS_G), and therophytes (Th_R) seem to be more resistant to grazing. Studying the impact of grazing management on the plant life form types provides useful information to find the most adapted species for rangeland sustainability all around the world.

Native prairie grasslands are a fundamental part of Canada's natural heritage, but these formerly extensive ecosystems have undergone declines due to grassland conversion and fragmentation. In addition, remaining native grasslands are threatened by invasive non-native plants, which can outcompete native flora and negatively impact ecological functioning. Although several studies have reported invasions in northern prairie grasslands, only some have investigated patterns across a large spatial gradient, and few have tested their relationship with environmental predictors and anthropogenic disturbance. We surveyed 139 plots across a 938-km spatial gradient in Alberta to 1) identify the most frequent and abundant nonnative species, 2) test whether levels of non-native plant invasions are linked to environmental factors or anthropogenic disturbance, and 3) inspect whether relationships differ between mesic and semiarid grasslands. Data were analyzed using generalized additive models and commonality analysis.

Our results show that Kentucky bluegrass (Poa pratensis subsp. angustifolia), commonly used for agronomic purposes, is by far the most frequent and abundant non-native plant in Alberta grasslands. Across all plots, abundance and richness of non-native plants were positively linked to a shared effect by aridity, soil texture, and agricultural activity. Furthermore, the importance of predictors differed between mesic and semiarid grasslands. In mesic grasslands, non-native plant abundance and richness were highest in areas with high agricultural activity and fine-textured soils. In the semiarid prairie, topography accounted for most explained variation in the levels of invasion. In summary, climatic conditions, and to some extent agricultural activity and topography, best explain the patterns of non-native plant invasions. A priority for future research is to identify the mechanisms underlying the differences in invasion across mesic and semiarid prairie grasslands. To counteract invasions, practitioners need to diminish the propagule pressure by invasive agronomic grasses, protect and restore grasslands remnants in the mesic region, and proactively control new invaders.

Construction of small ponds that collect and store rainwater to be used for livestock watering has been one of the most widespread adaptive solutions in Iberian rangelands to cope with water scarcity, a problem that has become particularly relevant in recent decades due to the progressive increase in livestock density on farms. However, watering ponds can also be a source of health problems due to the consumption of low-quality water by livestock. In this study, we analyzed the physico-chemical and microbiological quality of water from a set of watering ponds located in Iberian rangelands and evaluated its suitability for livestock consumption by comparing the analytical results with internationally recognized water standards for livestock. In addition, seasonal and spatial variations in pond water quality and the influence of some physical and managerial factors were assessed by multivariate statistical analysis. Results showed a high seasonality in pond water composition. The quality of pond water was sufficient to be used for livestock during the rainy season, but high bacterial pollution of fecal origin was evidenced at the end of the dry season in many ponds, with consequent risk for animal health. Dilution by rainwater and evapo-concentration processes were the main mechanisms that determined the concentrations of contaminants in pond water, while livestock density did not seem to have a significant influence. We propose some strategies, such as diversification in water supply sources and regular water quality testing, that farmers could adopt to deal with the detected water quality problems.

Seed-based restoration of native forb species, in the Intermountain region of the western United States, is challenged by a limited understanding of conditions that contribute to establishment success. This study evaluated the differential effects of row cover and a range of sowing depths, which influence soil microclimate, on 20 common native perennial forb species across three sites and 2 yr with and without row cover.

Seedlings were counted the spring and fall following the planting year. We hypothesized that larger-seeded species would be more tolerant of deeper seeding depths while small-seeded species would establish better at the shallowest depth increment and that emergence would be better under the row cover. Overall, emergence was low with rates between 0.2% and 1.0% for 16 of the 20 species. Three species emerged between 1% and 2.4% while barestem biscuitroot (Lomatium nudicaule [Pursh] J.M. Coult. & Rose) averaged 6.9%. Environmental factors related to site and seeding year had greater effects on emergence than row cover or seeding depth. Row cover led to generally higher emergence. Deeper seeding depths within the range for rangeland seeding equipment tended to have detrimental effects on emergence, though the effects of seeding depth varied by site, year, and species. Emergence for large-seeded species (2.3%) was significantly greater than small-seeded species (0.5%), but neither were different than medium-seeded species (0.62%).

This outcome highlights the challenges restoration practitioners face in the intermountain region. While using the best techniques and most appropriate plant materials improve the chances of successful restoration, largely uncontrollable and often unpredictable factors represented by site and weather variability will continue to be driving factors in semiarid regions.

California ground squirrels (Otospermophilus spp.) cause more economic damage to California rangelands than any other rodent. Damage comes in many forms, although forage loss is typically the greatest concern. These losses are believed to be significant for ranchers, particularly given the economically marginal environment in which they exist, yet our understanding of these economic losses is limited. Furthermore, current public opinion is often not supportive toward ground squirrel control on many public grazing lands. Information on the damage that ground squirrels cause to rangelands may be needed to justify management actions in the future. Therefore, we evaluated the amount of standing crop removed by California ground squirrels across 16 sites at four different ground squirrel density categories in central California rangelands from 2019 through 2020. We also included precipitation and livestock grazing intensity to help account for their potential effect on forage production. We found that ground squirrel abundance negatively affected standing crop biomass, with available forage reduced by 27.2 kg ha^–1 per individual ground squirrel at the end of the growing season. Likewise, precipitation influenced standing crop, with each cm of precipitation yielding a 16.6 kg ha^–1 increase in available forage. We did not observe any effect of livestock grazing intensity, an interaction between livestock grazing intensity and ground squirrel abundance, or an interaction between precipitation and ground squirrel abundance on residual standing crop. Collectively, this information will be useful to ranchers to help determine when control efforts may be needed for California ground squirrels given relative abundance of ground squirrels on their rangeland properties.

Nitrogen use efficiency (NUE) in plants is dependent on various factors including nitrogen availability and root morphology. This study investigated changes in root morphological and growth features in response to plant community structures in legume-grass mixed pastures. Three types of legume forage and three gramineous forage were selected, including Bromus. innermis, Onobrychis. viciaefolia, Phleum pretense, Trifolium. pretense, Dactylis glomerata, and Medicago sativa. The effects of different community structures on changes in the land equivalent ratio, crowding, aggressivity, and competition, as well as the NUE, N yield, and root morphologies, were investigated. It was found that mixed seeding combinations increased the forage yield significantly but increasing the number of mixed seeding species did not further affect the herbage yield. Both the root lengths and root specific areas of the forage grass increased with increasing spatial distance, indicating that while the root morphology of the grass was controlled by genetic factors, the phenotypic characteristics of forage grass were changed by the balance between aboveground and underground growth. Root morphology was found to play a significant role in the NUE and the relation between specific root area of legume and LN(W_N), specific root length of grass, and LN (W_Nt) can be expressed by the binomial function model.

Variation in the relative abundance and biomass of arthropods has important potential consequences for insectivores. We studied the influence of temporal variation and habitat management (i.e., burning and strip-disking) on the availability of potential arthropod prey for brooding northern bobwhites (Colinus virginianus) in the mixed-grass prairie of western Oklahoma. Burning changed the composition of the arthropod community by biomass, but disking did not result in any community-level changes. Burning also increased the total abundance and biomass of arthropods collected compared with the control, but disking did not affect total abundance or biomass. Temporal variation exerted a broader influence on arthropods, and total abundance and biomass increased throughout the duration of the sampling period (May-July) at paired burn/control and paired disked/control sites. Ants, which had the highest abundance and biomass of any taxa, appeared to drive these patterns. The response of individual orders to management and temporal variation varied in size and direction, though we observed more and stronger effects of temporal variation than burning or disking. These results support the idea that burning provides benefits to foraging bobwhite broods through increased total availability of arthropod prey, as well as favorable habitat characteristics (i.e., bare ground, structural heterogeneity). Large temporal variation in total arthropod abundance and biomass, as well as that of individual orders, likely also influences the relative importance of individual prey items in the bobwhite diet based on the timing of nest initiation and hatching. A better understanding of how these temporal and management-induced shifts in arthropod availability influence potential nutrient gains and limitations for bobwhites will require data on macronutrient content and digestibility (i.e., exoskeleton) of prey taxa.

Expanding distributions of native juniper species have had significant ecological and economic impacts on prairie ecosystems of the Great Plains. Juniper encroachment reduces rangeland production by decreasing herbaceous biomass and affecting natural ecosystem functions as it alters other native plant communities, microclimates, and soils. Juniper distribution maps are needed to support proactive management, but they often underestimate the extent of low-density juniper stands. Our objectives were to extend a previous juniper mapping study by 1) fitting a predictive ecological model for low-density (< 15% fractional cover) juniper stands and assessing the classification accuracy, 2) determining the habitat variables that had the strongest associations with low-density juniper, and 3) applying the model to map low-density juniper stands, where proactive management has the greatest potential for stopping further juniper encroachment. The study area included counties bordering the Missouri River in southeastern South Dakota and northeastern Nebraska covering approximately 23 000 km². Environmental predictors included seed source distance and density, as well as topography, climate, soils, and land use variables. Areas of low-density juniper were identified by visual interpretation of sample plots from digital aerial photography. We used a machine-learning approach to classify low-density juniper with the random forests algorithm. Model accuracy was high with an area under the receiver operating characteristic curve of 0.884. Variables related to seed sources were the most important predictors, and precipitation, slope angle, and the local intensity of human land use also had substantial influences. A previous map based on Landsat imagery identified 209 968 acres (84 971 ha) as juniper with in the study area, and this study found an additional 430 648 acres (174 277 ha) classified as low-density juniper stands. These results can provide agencies and land managers with more accurate information about the distribution of juniper, and the underlying techniques can be extended to map woody plant encroachment in other areas.

Encroachment of woody plant species on rangelands is of critical concern for rangeland health and function. Recent advances in unpiloted aerial vehicles (UAVs) technology have opened new opportunities for natural resource personnel to quantify features within the landscape. Our goal was to combine information derived from UAV and Sentinel-2 imagery to quantify the presence and spatial distribution of mesquite (Prosopis glandulosa). The specific objectives were to 1) evaluate the accuracy of UAVs to estimate mesquite height and 2) classify mesquite using a combination of height metrics and spectral information by combining UAV and Sentinel-2 remote sensing data. We conducted our study in three different ecoregions in Texas. We collected on-site tree height field measurements and created two UAV-derived height outputs at 50 m and 100 m above ground level (AGL). We then used a random forest classification with data derived from the UAV to inform Sentinel-2 imagery of mesquite locations to assess its presence at the landscape level. Linear regression analysis showed that 50-m AGL mesquite height estimates from UAV explained 95% of the variability. Variability explained from 100 m AGL height estimates was slightly lower at 92%. Accuracy assessments from using UAV training data to predict mesquite presence using Sentinel-2 imagery yielded overall accuracy of > 80% for all sites, user accuracies up to 86%, and producer accuracies up to 92%. UAV-derived heights of mesquite were reliable. UAV imagery can be used as training data for Sentinel-2 satellite imagery to assess mesquite presence on Texas rangelands. Being able to combine the high spatial resolution of the UAV imagery with the high temporal resolution of the Sentinel-2 satellite imagery could improve our ability to use UAVs to monitor rangelands.

The effect of mowing frequency on cumulative dry matter yield (cDMY) in Leymus chinensis has been well studied. However, how biomass and nitrogen or phosphorus allocation among leaf, stem, and sheath of L. chinensis contribute to its cDMY under different mowing frequencies remains unclear. A 2-yr field experiment with five mowing frequencies was conducted to study effects of mowing frequency on biomass allocation and yield of L. chinensis. The mowing frequency treatments were extremely heavy mowing, heavy mowing, moderate mowing (MM), and light mowing (LM) in contrast with single mowing as the control (CK). In general, as mowing frequency increased, the cDMY of L. chinensis decreased (P < 0.05). The cDMY on the MM and LM treatments was equal or greater than that on the CK treatment in both years. Leaf biomass and leaf-to–individual tiller ratio of L. chinensis decreased as mowing frequency increased due to shorter recovery time, although the N and P concentrations of leaves were higher. The leaf-to–individual tiller ratio increased exponentially (P < 0.001), while the cDMY increased linearly (P < 0.001) with increased leaf biomass. Furthermore, stem and sheath biomass of L. chinensis were significantly lower in all mowing frequency treatments (P < 0.05) compared with the CK treatment, but no changes were observed in stem and sheath between mowing frequency treatments in both years. Our results reveal that leaf biomass primarily contributed the most to cDMY, and increased mowing frequency profoundly altered the biomass allocation among leaf, stem, and sheath. It is recommended that MM or LM be optimal to efficiently promote dry matter yield and maintain root biomass of L. chinensis.

Prescribed burning is sometimes advocated as a means for controlling Kentucky bluegrass (POPR) in invaded grazing lands. However, little is known about the effects of fire on POPR seed survival. We exposed seeds of POPR (c.v. Kenblue), placed in shallow metal dishes, at ground level to prescribed burns while monitoring temperature at the soil surface and at 10 cm above ground with thermocouples and assessed subsequent seed germinability. Maximum surface temperatures during the test burns averaged 271°C ± 23°C but varied widely (range 41°C–509°C) while maximum temperature at 10 cm above ground was slightly higher (301°C ± 25°C). Burning inhibited seed survival or the ability to germinate (Kolmogorov-Smirnov P < .0001). Germination of the POPR seeds in the control dishes averaged 93% ± 1%. Average germination for burned locations was 37% ± 7% and was distributed bimodally; it was absent or strongly inhibited in 59% of the samples but much less affected (≥ 60% normal germination) in the remaining 41% of locations. Germination success was similar in burned plots previously managed with both grazing and fire (35% ± 10%) or previously managed by fire alone (38% ± 11%), but it was significantly and inversely correlated to maximum surface temperature during the burn (Spearman r = –0.49, P < 0.005). However, we observed a binary pattern of high and low seed germination response across the entire gradient of recorded surface temperatures, including instances of highly disparate values for seed survival in samples located within 60 cm of each other. Such extreme variability may result from unburned or superficially affected safe sites that originate from heterogeneity of fire impacts. This study suggests prescribed burning can kill POPR seeds near the soil surface, especially those located in standing litter and dry thatch. However, some seeds under these layers and closer to the mineral soil surface may be less impacted.

Seed-based restoration of wildlife-important shrubs following wildfire is a management priority in many ecosystems. However, postfire restoration success is spatiotemporally variable and establishment from seed frequently fails in arid and semiarid rangelands. There may be opportunities to improve restoration success by taking advantage of small-scale spatial variability in environmental characteristics. Woody plants create distinct postfire microsites, which may influence establishment and growth of seeded species, under their canopies (canopies) compared with between their canopies (interspaces). Immediately after fire, former canopies generally have less vegetation and greater soil nutrient concentrations compared with interspaces. Thus, former canopy compared with interspace microsites may be more favorable for establishment and growth of seeded species, but rapid exotic plant invasion of former canopy microsites may hinder success. We evaluated seeding bitterbrush (Purshia tridentata Pursh DC) after wildfire in former western juniper (Juniperus occidentalis ssp. occidentalis Hook) canopy compared with interspace microsites at six locations for 3 yr post seeding. Bitterbrush abundance was 3.6-fold greater in former canopy compared with interspace microsites after 3 yr. Bitterbrush height was 1.5 to 2.5-fold greater in former canopy compared with interspace microsites. The first year after fire, exotic annual grass cover was 15.6-fold greater in interspace compared with canopy microsites. Abundance and cover of other herbaceous vegetation were generally also greater in the interspace. Exotic annual grass and native bunchgrass abundance increased substantially over time in former canopy microsites, suggesting abundant resource availability. Less herbaceous competition and presumably greater resource availability in former canopies probably resulted in greater success of seeded bitterbrush. These results suggest that capitalizing on spatial variability in environments can be used to increase restoration efficiency. After fire in western juniper–encroached rangelands, former juniper canopy microsites are a favorable environment for establishment and growth of seeded bitterbrush and could be targeted for restoration efforts to improve efficiency.

Non-native grass invasion is a leading driver of biodiversity loss and degradation of rangeland ecosystem services. The reproductive mode and output of alien species mediate invasion, and their differential propagule pressure has implications for management outcomes. Propagule success, however, is context dependent. Resource availability promotes invasion and is heavily influenced by disturbance regimes. This study measured the reproductive phenology and establishment of Guinea grass's vegetative and seed-based reproduction in the field and the greenhouse. We asked how differences in vegetation type (woodland vs. grassland), disturbance history (brush management), and their interaction mediate the invasion process of Guinea grass. We documented differences in reproductive phenology as a function of vegetation type and disturbance history in the field. We measured seedling emergence and establishment in the greenhouse by fully crossing environmental variables with soils from two different disturbance levels. Finally, we estimated propagule pressure across vegetation types and disturbance history using data collected from the field and greenhouse trials.

We found that areas associated with higher soil nutrients (under nitrogen-fixing mesquite trees and soil disturbance) had higher seed and stolon propagule pressure. Conversely, low disturbance and grassland areas had lower propagule pressure and were associated with lower nutrients. In the greenhouse, seedling establishment interacted with vegetation and disturbance. Seedlings growing in soils from mottes in a high-disturbance pasture had higher biomass and shoot length. However, the low disturbance pasture's specific root length was highest in mottes, indicating a higher allocation to roots, investing toward resource capture. Subsequently, we posit a hypothesis for Guinea grass spread in South Texas. Our findings suggest potential management steps, including treating Guinea grass under wooded cover to reduce overall propagule pressure and minimize soil disturbance during brush management of partially invaded woodlands.

Ecological sites comprise a land classification system that represents potential vegetation states and their management needs for different soils and climates. In the Rio Grande del Norte National Monument (RGdNNM) in northern New Mexico, uncertainty about the patterns and drivers of vegetation states impedes sustainable land management. Similar challenges are ubiquitous across terrestrial ecosystems and in particular landscapes with high spatial variability in soils and climate. Lack of suitable data has been a barrier to large-scale ecological site development based on quantitative observations. We used data from existing federal monitoring programs alongside spatial, environmental, and land use data to test for the role of climate, geomorphology, soils, and land use history on vegetation communities in RGdNNM. The monitoring dataset was collected with standardized monitoring methods implemented by the Bureau of Land Management's Assessment, Inventory, and Monitoring program and the Natural Resources Conservation Service's Landscape Monitoring Framework program. Eleven ecological site concepts and paired vegetation communities were identified using multivariate fuzzy clustering and classification tree analysis to determine the influence of abiotic variables on vegetation communities. The ecological site and vegetation community concepts developed for RGdNNM demonstrate how existing monitoring data can be used to interpret the structural and functional characteristics of landscapes. A workflow for applying monitoring data to landscape classification is presented to support the broader framework for ecological site development.

Livestock grazing often intensifies around herder camps, which can lead to degradation, particularly in arid areas, where vegetation is scarce. In Mongolia, nomadic herders have covered long distances between camps and changed camps regularly for centuries. However, changing socioeconomics, rising livestock numbers, and climatic change have led to growing concerns over rangeland health. To understand travel mobility and livestock grazing patterns, we combined Global Positioning System tracking data of goats, remotely sensing pasture productivity, and ground-based vegetation characteristics in the Great Gobi B Strictly Protected Area, Mongolia. We assessed herder preferences for camp selection, followed 19 livestock herds over 20 months, determined use and nutrient contents of the most dominant plant communities, and estimated plant species richness, vegetation cover, and biomass within different grazing radii around camps. Biomass availability was key for herder decisions to move camps, but in winter, other factors like shelter from wind were more important. Camps were mainly located in Stipa spp. communities, agreeing with herder preferences for this highly nutritious species, and its dominance around camps. Herders changed their camp locations on average 9 times yearly, with a maximum distance of 70–123 km between summer and winter camps, and an average visitation period of 25–49 d per camp, depending on season. Small livestock spent > 13–17 h daily within a radius of 100 m from camp, and livestock use intensity decreased steeply with distance from camp but was remarkably similar around spring, autumn, and winter camps on the Gobi plains. However, we found little evidence for a corresponding gradient in plant species richness, biomass, and cover on the Gobi plains. The high mobility of local herders and the overriding impact of precipitation on pasture dynamics contribute to a sustainable vegetation offtake by livestock in the nonequilibrium rangelands of the Dzungarian Gobi.

Administrative oversight of grazing on public land requires efficient and reliable rangeland monitoring. In a portion of the Bighorn National Forest of Wyoming, the US Forest Service uses the modified Robel pole as a monitoring tool to measure residual herbaceous biomass after grazing. Questions about the vegetation standards have persisted for decades. From 2018 to 2020 we quantified relationships between herbaceous biomass and visual obstruction across spatial, temporal, management, and topoedaphic gradients in 11 grazed pastures selected mutually by stakeholders. Initial standards were developed on the basis of 1 yr of research, and state visual obstruction readings (VORs) were correlated with biomass with an R² = 0.81, yet our research resulted in R² values of approximately half (ranging from 0.39 to 0.45) with significantly different slopes 2 of 3 yr. Moreover, the intercepts for each year individually, when averaged, or when combined were always greater than the relationship used to develop initial standards, resulting in 140–564 more kg per ha of biomass at the 5-band standard level, or situations where lower band levels (2.5–3.9) would yield similar biomass levels. In addition to VOR and biomass, slope, aspect, plant and ground cover, weather, and livestock management variables were assessed with information theory models for predicting residual biomass. The top model included VOR, slope, exotic grass, and temperature. This suggests that greater knowledge of the site will increase understanding of biomass production on the site and help to mitigate disagreements among stakeholders by tailoring expectations to variable sites. Finally, the higher intercepts in all of our models may explain the persistent skepticism about the application of the original standard and provide the opportunity to refine standards to better match postgrazing monitoring with resource objectives, particularly if functional group dominance on these sites have changed over time.