Rangeland managers need tools to control invasive annual grasses, particularly following wildfire. We assessed responses of native and invasive/exotic grasses to the MB906 soil amendment containing live cultures of a purportedly weed-suppressive strain of the bacterium Pseudomonas fluorescens (“WSB”). MB906 was applied alone and in combination with the pre-emergent herbicide imazapic on >3000 ha across three sagebrush-steppe landscapes burned several months prior. Replicate plots of each treatment type were established and plant cover was measured in the following three years. Cover of invasive-annual grasses (“IAG”) was not responsive to MB906 when all IAG species were considered (“IAG-All”). However, MB906 led to a 54% reduction in the IAG's that were previously reported to be controlled by WSB (“IAG-Target”) in the second year following application (IAG-Target = cheatgrass, Bromus tectorum and medusahead, Taeniatherum caput-medusae; IAG-All also includes Vulpia myuros and Bromus arvensis). MB906 reduced the effectiveness of co-applied imazapic: Imazapic alone reduced IAG-All by 83% and 68% in years 1 and 2, respectively, while imazapic+MB906 reduced IAG-All by 48% and 38% in years 1 and 2, respectively, across all landscapes, and a similar response pattern was observed for IAG-Target. Perennial grass cover was unaffected by the treatments except where it increased 4-fold in response to imazapic applied at a high rate (0.140 kg a.i. ha^–1) in one of the landscapes. Tank mixing MB906 and herbicide may have lessened the biological activity of the herbicide by altering the pH or mineral content of the spray solution or by direct metabolism of the herbicide by the bacteria. These results do not provide strong support for MB906 as a tool for annual grass control, though they suggest further investigation may be warranted.

We conducted two case studies testing effectiveness of a soil-borne bacteria, Pseudomonas fluorescens strain D7, in controlling Bromus tectorum (cheatgrass) when mixed with native seeds sown after a fire and when sprayed on a native community with high abundances of B. tectorum. Each case study area (162 ha) compared treatments with D7 present and absent and was replicated four times (20.3 ha each) in a completely randomized design. Response variables (foliar cover, aboveground biomass, and density of B. tectorum; density of sown native plants) were measured pretreatment for the sprayed area and each year for 3 yr after treatment at both study areas and were evaluated as a repeated measures analysis. Foliar cover, biomass, and density of B. tectorum with sprayed or seed mixture applications did not differ between D7-treated and untreated areas at any time within the study (F_1,6 ≤ 1.42; P ≥ 0.28). D7 as a seed mixture did not significantly impact densities of native seedlings (F_1,6 = 1.27; P = 0.30) at any time during the study. Results contrasted with previous D7 studies that showed effective control of B. tectorum within 3 yr of treatment. Since bioherbicidal methods are being commonly applied, we believe that reporting negative results is important for future meta-analytical studies that provide managers with information on the likelihood for weed-suppressive bacteria to effectively control weeds.

Downy brome (Bromus tectorum) is one of the most problematic invasive plant species in the United States. Downy brome invasions are associated with reductions in diversity and an increase in fire intensity. Bioherbicides that are reported to effectively control downy brome have been developed. Pseudomonas fluorescens strain D7 is one such bioherbicide that is of significant interest to land managers in Wyoming. A spatially replicated field trial was performed to identify what effect D7 has on downy brome in Wyoming. The field trial showed no response of any downy brome fitness metrics to D7; only commonly used synthetic herbicides were able to reduce downy brome cover. This work suggested D7 may not be a viable product for downy brome control, or more information may be needed about the field conditions required for a positive result when using D7.

Approaches and techniques for control of exotic annual grasses are a high priority in rangelands including sagebrush steppe. Strains of the soil bacterium Pseudomonas fluorescens have been proposed to be selectively pathogenic to multiple species of exotic annual grasses (“Pf,” weed-suppressive bacteria, “WSB”). However, defensible tests of the target and nontarget effects of these WSB strains in the field are needed. We evaluated the effects of D7 and MB906 strains of Pf WSB in sagebrush steppe invaded by cheatgrass (Bromus tectorum L), medusahead (Taeniatherum caput-medusae L. Nevski), and other exotic annual grasses. We evaluated the WSB strains with and without herbicides (imazapic, rimsulfuron) or discing to mix surface-spray of the WSB into deeper soils, and we replicated these tests in three ecoregions that differed in soils and climate. Over 3 yr after treatment, neither WSB strain affected cover of exotic annual grasses, perennial bunchgrasses, or the total community, either with WSB alone or in combination with herbicides or discing. WSB has received considerable attention and is being applied across large rangeland areas, but the WSB strains and methods applied here were ineffective. We recommend any future use of WSB be applied in an experimental fashion, with experimental design and measurement of responses, until its effects can be proven.

The exotic winter annual grass Bromus tectorum L. (downy brome or cheatgrass) infests millions of hectares of western rangelands. Weed-suppressive bacteria (ACK55 and D7 strains of Pseudomonas fluorescens Migula 1895) have been shown to reduce B. tectorum populations in eastern Washington. Unfortunately, outside of Washington, little is known about the efficacy of these or other weed-suppressive bacteria. We used Petri-plate and plant-soil bioassays to test effects of ACK55 and D7 on B. tectorum from Montana and Wyoming. We also tested effects of ACK55 on B. tectorum at six field sites in Montana and one in Wyoming. P. fluorescens reduced B. tectorum germination and root and shoot lengths in Petri-plates but had no effect on plants during growth chamber plant-soil bioassays or field experiments. Bromus arvensis L. (field brome or Japanese brome), a species similar to B. tectorum, was prevalent at two of our sites, and ACK55 was ineffective against B. arvensis as well. Our findings contribute to a growing body of evidence that the ACK55 and D7 strains of P. fluorescens are not reliable tools for controlling B. tectorum in the Northern Great Plains, Central Rocky Mountains, and elsewhere.

Long-term control of the invasive annual grass cheatgrass is predicated on its biological suppression. Perennial grasses vary in their suppressive ability. We compared the ability of a non-native grass (“Hycrest” crested wheatgrass) and two native grasses (Snake River wheatgrass and bluebunch wheatgrass) to suppress cheatgrass. In a greenhouse in separate tubs, 5 replicates of each perennial grass were established for 96 d, on which two seeds of cheatgrass, 15 cm apart, were then sown in a semicircular pattern at distances of 10 cm, 30 cm, and 80 cm from the established perennial bunchgrasses. Water was not limiting. After 60 d growth, cheatgrass plants were harvested, dried, weight recorded, and tissue C and N quantified. Soil N availability was quantified at each location where cheatgrass was sown, both before sowing and after harvest. Relative to cheatgrass grown at 80 cm, all perennial grasses significantly reduced aboveground biomass at 30 cm (68% average reduction) and at 10 cm (98% average reduction). Sown at 10 cm from established perennial grasses, cheatgrass aboveground biomass was inversely related with perennial grass root mass per unit volume of soil. All cheatgrass sown at 10 cm from “Hycrest” crested wheatgrass died within 38 d. Before sowing of cheatgrass, soil 10 cm from established perennial grasses had significantly less mineral N than soil taken at 30 cm and 80 cm. Relative to cheatgrass tissue N for plants grown at 80 cm, cheatgrass nearest to the established perennial grasses contained significantly less tissue N. All perennial grasses inhibited the NO₂^– to NO₃^– nitrification step; for “Hycrest” crested wheatgrass, soil taken at 10 cm from the plant had a molar proportion of NO₂^– in the NO₂^– + NO₃^– pool of > 90%. In summary, a combination of reduced nitrogen availability, occupation of soil space by perennial roots, and attenuation of the nitrogen cycle all contributed to suppression of cheatgrass.

The objective of this study was to determine if the stability of water temperature attributes suggested by an analysis conducted in 2003 (Larson and Larson 2001; 2003) was continued over a 20-yr period. The pattern of degree accumulations observed in the daily heating and cooling cycles of three streams in 1998, 2013, 2014, 2016, and 2018 were studied in Grant County, Oregon. The average air and water temperatures remained stable at each site and followed the expected natural patterns (Larson and Larson 2001) described in an earlier study. Within each sampling year, mean air and water temperature remained within 1–2°C and there were no significant differences between the rates of heating between the study years or between sites.

Agrosilvopastoral systems have been promoted as sustainable models that combine crops, livestock grazing, and forestry in the same area. We hypothesize that agrosilvopastoral systems can improve soil C and N stocks over time. Therefore, in this study, we aimed to evaluate the changes in soil C and N stocks after conversion of low-productivity pasture into well-managed pasture and agrosilvopastoral land in the Brazilian Cerrado. Soil samples were collected in 2016 and 2018 at 0–5, 5–10, 10–20, and 20–30 cm depths from the following areas: integrated crop-livestock-forest (ICLF), marandu grass (Brachiaria brizantha) monoculture (MAR), low productivity pasture of signal grass (Brachiaria decumbens) monoculture (PAST), and native vegetation (NV; “Cerrado”). The C and N content and stocks, ¹³C natural abundance, and C contents in the physical and chemical fractions of soil organic matter (SOM) were measured. The ICLF and MAR systems promoted faster recovery of soil C and N stocks at all soil depths compared with PAST. The C content of the free light fraction of SOM under the ICLF and MAR systems increased, reaching values similar to NV up to 20 cm. The C content was higher in the humin fraction at all depths in all areas, and for this measurement, the ICLF system performed remarkably compared with PAST at a depth of 5–10 cm. Our findings support the hypothesis that conversion of low-productivity pasture into agrosilvopastoral and actively managed pasture systems leads to improvements in soil quality and C and N stocks in the Brazilian Cerrado.

Forage and grazing (FG) systems can store a substantial amount of soil organic carbon (SOC) under appropriate land use management and reduce atmospheric CO₂ concentrations. Increasing SOC levels along with many interlinked ecosystem services are essential for increased productivity and sustainability of FG lands (FGLs). Although adoption of improved management practices (MPs) that support SOC sequestration (SOC_q) is necessary, clear understandings of challenges and opportunities which are sometimes unique to individual FGLs, are also important for implementation of MPs. The objective of this forum paper is to explore the latest scientific knowledge on opportunities to address major challenges for increasing SOC_q in FGLs. In intensively managed FGLs where the goal is often to maximize yields, lands are heavily fertilized and thus, usually drive towards SOC loss. Diversifications of both forage and grazing species along with strategic grazing plans have been proven as effective MPs for increasing SOC_q. However, challenge of maintaining productivity levels still remains. Implementing improved grazing for nutrient cycling and integrating forage diversification for increased biodiversity are found to improve soil health attributes, which are critical for SOC_q. However, to achieve this, we also need to consider site- and soil- specific factors. Extreme climatic events often lead to a decline in soil fertility status, SOC_q and overall productivity of FGL systems. To address these challenges, uses of models to simulate the FGL systems and have definite choices of suitable MPs are helpful. However, we must be able to access a wide range of datasets to develop system-level adaption strategies that are effective in mitigating these adverse effects. Ultimately, participatory research with novel views and improved perceptions based on the value of SOCq and long-term benefits of the implementation of the best MPs and developing education and outreach materials to enrich the producers' knowledge gaps are helpful for climate-resilient FGL systems.

A comprehensive understanding of multipaddock, rotational grazing management on rangelands has been slow to develop, and the contribution of adaptive management (Briske et al. 2011) and sufficient scale (Teague and Barnes 2017) have been identified as key omissions. We designed an experiment to compare responses of vegetation and cattle in an adaptively managed, multipaddock, rotational system with that of a season-long, continuous system at scales comparable with those of a working ranch. We hypothesized that 1) year-long rest periods in the adaptively managed, rotational pastures would increase the density and productivity of perennial C₃ graminoids compared with continuously grazed pastures and 2) adaptive management, supported with detailed monitoring data, would result in similar cattle performance in the rotational as in the continuously grazed pastures. However, we found little supporting evidence for grazing management effects on C₃ graminoid abundance or production under either above-average or below-average precipitation conditions during the 5-yr experiment. Furthermore, adaptive rotational grazing resulted in a 12–16% reduction in total cattle weight gain relative to continuous grazing each year. Our work shows that the implementation of adaptive management by a stakeholder group provided with detailed vegetation and animal monitoring data was unable to fully mitigate the adverse consequences of high stock density on animal weight gain. Under adaptive rotational grazing, C₃ perennial grass productivity and stocking rate both increased following above-average precipitation. But when adaptive rotational management was directly compared with continuous grazing with the same increase in stocking rate, continuous grazing achieved similar vegetation outcomes with greater cattle weight gains. We suggest that managers in semiarid rangelands strive to maintain cattle at stock densities low enough to allow for maximal cattle growth rates, while still providing spatiotemporal variability in grazing distribution to enhance rangeland heterogeneity and long-term sustainability of forage production.

The conversion of oasis-desert ecotones for agricultural use is a recent and ongoing trend. To evaluate the impacts of different land-use types and disturbance intensities (distance from farmland) on ecotonal vegetation, we investigated the plant community structure and growth of dominant species in an oasis-desert ecotone in the southern Taklimakan Desert. We established six 100 × 100 m plots, each associated with a particular land-use type in two respective locations: farmland margins and peripheral desert. Twelve and five species, respectively, were recorded at these two sites, with the latter containing fewer annual species. Species richness in the ecotone corresponded to the size of the investigated area. Plant coverage was generally two to eight times higher in the farmland margins than in peripheral desert areas. The species richness, plant coverage, and diversity indices at the two sites varied according to the land-use type. An increased distance from farmland corresponded to changes in the community structure for some land-use types, whereas in most instances, species richness differed by only one species within 100 m of farmland. Plant density and coverage were relatively higher in subplots located 0–20 m away from farmland than in other subplots, although these differences were nonsignificant. Whereas land-use types affected some of the growth indices of the dominant species Alhagi sparsifolia, we observed few significant distance effects. These results indicate that plant community structures and the growth of dominant species vary with landscape heterogeneity or land-use type. The distance effects are dependent on the land-use type. Over a short time period, irrigation is beneficial for the establishment of annual plants around farmland, but it is not beneficial for perennial plants that use ground water. However, further assessments of the long-term effects of agricultural activities on plant community structures, especially on dominant shrubs, are needed.

Solarization (covering soil and vegetation with plastic) has long been used in agriculture to control undesirable plants, but solarization of invasive plants in rangelands has shown mixed and species-specific results. Yellow bluestem (Bothriochloa ischaemum (L.) Keng var. songarica (Rupr. ex Fisch & C.A. Mey) Celarier & Harlan), an invasive perennial C₄ grass, is common throughout the southern Great Plains and is not controlled by winter prescribed fire. We tested whether solarization (tarping) with black plastic, combined with winter prescribed fire, could control yellow bluestem. We applied three treatments (with four replicates): solarization (August to November 2017) + fire (January 2018), trimming + fire, and fire only. Results after two growing seasons show that total yellow bluestem cover in solarized + fire plots was reduced to 54% ± 10% (mean ± standard error), lower than trimmed + fire (82% ± 5%, p < 0.01) and fire only plots (78% ± 6%, p = 0.01). Forb cover in solarized + fire plots (15% ± 4%) was much higher than trimmed + fire (4% ± 1%, p < 0.01) and fire only plots (3% ± 1%, p < 0.01). Native forb richness was only slightly higher in solarized + fire plots (16 ± 2 species) compared to fire only (10 ± 2 species, p = 0.08) and trimmed + fire plots (10 ± 1 species, p = 0.08). Interestingly, native forb richness in all plots increased compared to pre-treatment values (2 ± 1 species for all treatments, p < 0.01). Solarization + winter fire can slightly decrease yellow bluestem cover and greatly increase native forb cover, creating islands of diversity in otherwise low-diversity grasslands. However, repeated treatments or alternative techniques will be needed for full control of yellow bluestem.

Grassland birds have experienced protracted population declines, primarily due to loss and degradation of native grasslands. Restoration of native grasses may benefit grassland birds, but such restoration within the eastern United States has been limited. Production uses of native grasses (e.g., hay, pasture, biofuel feedstock) provide market-based incentives that could lead to more extensive use of these grasses than existing conservation-focused practices, potentially influencing breeding birds. Therefore, we compared breeding bird (n = 9 target species) relative abundance among 4 types of native warm-season grass (NWSG) agricultural production fields: forage (hay and pasture; n = 22 and 7, respectively), seed (n = 21), biofuel (n = 15), and a control (idle fields in conservation programs or practices; n = 37) in Kentucky and Tennessee, 2009–2010. We detected 2 145 birds, with field sparrow (Spizella pusilla, 43%) and red-winged blackbird (Agelaius phoeniceus, 27%) encountered most often. Relative abundance did not differ between production types and controls except for field sparrow (lower on seed production fields) and northern bobwhite (Colinus virginianus, lower on hay production fields). Species richness equaled or exceeded that of control fields for all production categories. We documented negative relationships between relative abundance and landscape-scale forest cover for four species (field sparrow, grasshopper sparrow [Ammodramus savannarum], eastern meadowlark [Sturnella magna], and red-winged blackbird) and positive relationships with amount of pasture and hay cover for four species (northern bobwhite, grasshopper sparrow, eastern meadowlark, and red-winged blackbird), reinforcing the importance of nonforested environments for these species. We conclude that production stands could be a viable approach for increasing NWSG available for breeding birds and, when established in the appropriate landscape context, can provide benefits similar to those provided by conservation programs.

Bearing in mind the current dramatic decline in biodiversity, in addition to preserving remaining natural habitat patches, performing successful habitat restorations and land-use is increasingly essential. In this study, the effect of patch size and connectivity on the early succession of orthopteran assemblages was examined in reconstructed Central European sand habitats. The first comprehensive study on this topic demonstrated that the diversity of the assemblages in mid-successional stages (4^th and 5^th years of research) reached the value which characterised the control areas. Grazing can preserve habitats in this successional stage. Based on the results of the study in sand habitats belonging to low-productivity dry grasslands, to maintain heterogeneous habitat structures, traditional moderate grazing is recommended. Grazing by sheep is the most beneficial for maintaining the presence of open surfaces, closed patches, and fallen foliage cover in optimal proportions for orthopterans. It was also revealed, that during habitat restorations of sand grasslands, patch size and connectivity affect the species richness of habitat specialist orthopteran species strongly.

Woodland and forest ecosystems across western North America have experienced increased density and expansion since the early 1900s, including in the widely distributed piñon-juniper vegetation type of the western United States. Fire suppression and grazing are often cited as the main drivers of these historic changes and have led to extensive tree-reduction treatments across the region. However, much of the scientific literature on piñon-juniper expansion dates back only to the early 1900s, which is generally half a century after Euro-American settlement. Yet US General Land Office (GLO) surveys provide valuable insight into the historical extent and density of woodland and forest ecosystems as surveyors would note where on the landscape they entered and exited woodlands or forests and provided qualitative estimates of relative tree density. This study uses these GLO surveys to establish piñon-juniper woodland extent in the late 19th century at the incipient stages of Euro-American settlement in southeastern Colorado and compares these data with 2017 aerial imagery of woodland cover. We found substantial amounts of woodland contraction, as well as expansion: ≈61% of historically dense woodland is now savanna or open (treeless), whereas ≈57% of historically open areas are now savannas or woodlands. The highest rates of expansion occurred on shallow, rocky soil types with low soil available water capacity, which support little herbaceous vegetation and were consequently less likely to be affected by fire suppression or grazing. Meanwhile, the significant contractions in woodland extent occurred on deeper, upland soils with higher soil available water capacity, which were likely where early settlement and tree cutting was most prevalent. Our results provide mixed support for the widespread assumption of woodland expansion since Euro-American settlement in southeast Colorado and suggest that the expansion that has occurred in our study area is unlikely a result of past grazing or fire suppression.

Monitoring rangelands by identifying the departure of contemporary conditions from long-term ecological potential allows for the disentanglement of natural biophysical gradients driving change from changes associated with land uses and other disturbance types. We developed maps of ecological potential (EP) for shrub, sagebrush (Artemisia spp.), perennial herbaceous, litter, and bare ground fractional cover in Wyoming, USA. EP maps correspond to the potential natural vegetation cover expected by environmental conditions in the absence of anthropogenic and natural disturbance as represented by the greenest and least disturbed period of the Landsat archive. EP was predicted using regression tree models with inputs of soil maps and spectral data associated with the 75th percentile of the Normalized Difference Vegetation Index in the Landsat archive. We trained our EP models with 2015 component cover maps on ecologically intact sites with relatively lower bare ground than expected. We generated departure of vegetation cover by comparing the EP and 2015 fractional cover. The departures represent land cover change from potential land cover and/or within-state changes in 2015. Next, we converted EP and 2015 fractional cover maps into thematic land cover and evaluated departure to determine if it was great enough to result in land cover change. The 2015 conditions showed reduced shrub, sagebrush, litter, and perennial herbaceous cover and increased bare ground relative to EP. Known disturbances, such as energy development, fires, and vegetation treatments, are clearly visible on the departure maps, but not on EP component maps. The most frequent departure from EP land cover was shrubland conversion to grassland. Land cover departures can be explained only in small part by known disturbance, and instead are ostensibly related to climate and land management practices. These drivers result in land cover departures that broadened the ecotone between shrubland and grassland relative to EP.

Huisache (Vachellia farnesiana [L.] Wight & Arn.) is a woody species native to the western hemisphere that can invade a variety of native rangeland habitats around the world. In South Texas, it is native yet increasing in density and range while displacing more desirable forage plants, and because it resprouts prolifically it has been difficult to control. We therefore attempted to characterize optimal timing and environmental conditions for herbicide control. We collected weather data in four huisache-invaded pastures along the Texas Coastal Bend and recorded the average huisache phenological stage at those pastures each month. We also analyzed root crown total nonstructural carbohydrate (TNC) and huisache mortality resulting from herbicide treatment each month between April 2012 and November 2014. Huisache mortality and TNC data were analyzed using a randomized complete block analysis of variance, with post hoc tests to separate means; Akaike's information criterion determined best-fit models for mortality data. Root crown TNC increased during May, August, and December, indicating downward translocation and the potential for increased mortality of treated plants. Actual mortality was greatest during the months of May, September, October, and November. The best fit model for mortality was a sixth-order polynomial function of mortality versus month; when month was removed as a model factor, the best fit model was a quadratic function of soil temperature (peaking at ≈24.5°C), combined with a quadratic function of phenology (highest at full canopy stage). These results indicate that huisache is best treated with chemicals when soil temperature is near 24.5°C and during the full canopy stage. In the coastal plains of South Texas these variables coincide with two windows of optimal mortality for huisache treatment: May and September–November.

Because drought impacts are accelerating due to climate change, drought preparedness on western rangelands matters now more than ever. Range professionals perceive, however, that many Utah ranchers remain ill-equipped for drought. The main research objective was to determine why ranchers often don't adopt recommended drought-mitigation tactics. Another objective was to clarify how grazing is managed during drought on federal lands. Fourteen tactics studied included management of water, forage, herds, and finances and access to information and government programs. Data collection included surveys of 429 ranchers and interviews of seven federal employees. Data analysis used descriptive statistics and logistic regression. Results indicated that 3,133 non-adoption decisions were heavily dominated by the perceived incompatibility between tactics and operational needs; producer situations may often be misunderstood by experts. Weather forecasting tools were typically regarded by ranchers as “too complex,” while Extension information was often viewed as “not useful.” Factors promoting drought preparedness included having a strong livestock-business orientation or a drought-planning mentality. Factors hindering drought preparedness were dominated by advancing rancher age. Grazing permittees benefit from federal drought early-warning systems, yet herd adjustments on allotments were rare during the 2019 drought, pushing forage utilization to the limits. While challenges appear daunting, there are opportunities to enhance drought preparedness, prominently including creative efforts to promote more education and mentoring on operational drought management. Comprehensive, user-friendly drought websites remain rare, yet they can be vital hubs for stakeholders. Such websites must meet diverse communication needs including a greater focus on information requirements of seniors. Drought policies for ranchers should: (1) Eliminate perverse incentives that foster inappropriate risk taking; (2) reward pro-active, risk-management behaviors; and (3) facilitate recruitment of a younger, innovative cohort of new producers. Updating federal management plans could support grazing adjustments that incorporate more grass banking. Unified drought-response guidelines could harmonize agency approaches.