The majority of native prairie has been lost throughout North America. Much of the remaining prairie is used for livestock grazing, so conservation of prairie species depends on sustainable grazing practices. Our objective was to evaluate the benefits of twice-over rotational grazing, in comparison with continuous season-long grazing and ungrazed “idle” fields, in conserving prairie songbirds. Northern mixed-grass prairie in southwest Manitoba, Canada is near the northern range limits for many endangered grassland birds, and thus is an important area for evaluating the contribution of twice-over grazing in the conservation of songbirds, including species at risk. In 2008 and 2009, we compared the relative abundances and diversity of grassland birds on 22 twice-over rotation, 15 season-long, and 8 ungrazed sites, using multiple 100-m fixed-radius point-count plots per site. Analyses were conducted using generalized linear mixed models. Although one obligate grassland bird, Savannah sparrows (Passerculus sandwichensis), had significantly higher relative abundances on twice-over than season-long sites in 2009, season-long pastures had higher species richness and diversity of obligate grassland birds in both years. Season-long grazing may actually benefit grassland bird communities by creating spatially heterogeneous but temporally stable areas of high and low livestock use within the pasture, thus increasing diversity of microhabitats. We found little evidence that twice-over grazing contributed to the conservation of grassland songbirds in subhumid northern mixed-grass prairies.

Grazing at high stocking rates may increase sediment and nutrient loading of pasture streams through transport in precipitation runoff and bank erosion. A 3-yr (2007–2009) grazing study was conducted on 13 cool-season grass pastures to quantify effects of stocking rate and botanical composition on forage sward height, proportions of bare and manure-covered ground, and bank erosion adjacent to streams. Pastures ranged from 2 ha to 107 ha with stream reaches of 306 m to 1 778 m that drained watersheds of 253 ha to 5 660 ha. Bare and manure-covered ground were measured at a 15.2-m distance perpendicular to the stream at 30.5-m intervals at up to 30 locations on each side of the stream by the line transect method in May, July, September, and November of each year. At the midpoint of the 15.2-m line, forage sward height was measured with a falling plate meter (4.8 kg · m⁻²) and plant species identified. In November 2006, fiberglass pins (1.6 × 76.2 cm) were driven 73.7 cm into the stream bank at 1-m intervals from the streambed to the top of the bank along 10 equidistant transect locations on each side of the stream to measure bank erosion during spring, summer, and fall of each year. Increasing pasture stocking rates increased manure-covered ground and decreased sward height, but did not affect proportions of bare ground. The greatest, intermediate, and least net soil erosion rates occurred during the winter/early spring, late spring/early summer, and late summer/fall seasons. Stocking rates between measurements, expressed as cow-days · m⁻¹ stream, were not related to bank erosion. Increasing stocking rates per unit of stream length will increase manure cover and decrease forage sward height, but not affect proportions of bare ground or bank erosion rates adjacent to pasture streams. Therefore, managing stocking rates may reduce nutrient loading of pasture streams.

The large-scale influence of livestock grazing in the western United States generates a need to integrate landscape management to incorporate both wildlife and livestock. The purpose of this project was to evaluate the effects of four different grazing cells (spring grazing, summer growing-season grazing, fall grazing, and resting) on wintering elk resource selection within the Wall Creek range in southwest Montana. We collected biweekly observations of elk (Cervus elaphus) numbers and distributions across the winter range from 1988 to 2007. Using a matched-case control logistic regression model to estimate selection coefficients, we evaluated the effects of annual green-up conditions, winter conditions, landscape features, and grazing treatment on elk group resource selection within the grazing system. We found that within the grazing system, elk groups preferentially selected for rested pastures over pastures that were grazed during the previous spring (1 May–1 June), summer (1 June–15 July), and fall (15 September–30 September). The strength of selection against the pasture grazed during the summer growing season was strongest, and pastures grazed during the spring and fall were selected for over the pasture grazed during the summer. The number of elk utilizing the grazing system increased in the 19 yr following implementation of the grazing system; however, total elk herd size also increased during this time. We found no evidence that the proportion of the elk herd utilizing the grazing system changed following implementation of the rest–rotation grazing system. Wintering elk group preference for rested pastures suggests rested pastures play an important role in rotation grazing systems by conserving forage for wintering elk. Additionally, rested pastures provide important cover for a host of other wildlife species. We recommend wildlife managers maintain rested pastures within rotation grazing systems existing on ungulate winter range.

Dung beetles are considered keystone species because of their role in decomposition, seed dispersal, and control of vertebrate parasites in grazed habitats. Despite the ecological importance of this group to pasture ecosystem functioning, still little is known about its relationship with grazing management activities. We evaluated the conservation value of protected areas for dung beetle diversity by comparing two different management conditions of Mediterranean savanna in central Spain. Four different sites with wild herbivory (red deer, roe deer) were sampled inside the Cabañeros National Park, and four sites with traditional agrosilvopastoral management were sampled in a sheep farm near the park. The dung beetle species richness was similar between savanna conditions, but the total dung beetle abundance and biomass were considerably greater in the park grasslands than in the grasslands of the sheep farm. Dung beetle species composition, species dominance, and abundance by functional groups from both park and farm sites were different, despite the high similarity among the sampled sites in both hydric content and dung availability. Onthophagus maki (Illiger 1803) and O. furcatus (Fabricius 1781) were the dominant species in the park, while O. furcatus, Aphodius foetidus (Herbst 1783), and Caccobius schreberi L. were the dominant species on the farm. Species richness and abundance of telecoprids were higher in the park than on the farm. Abundance of paracoprids was also higher in the park than on the farm, while no differences in species richness and abundance of endocoprids were observed between both conditions. These results suggest that management activities such as plowing and the use of veterinary substances affect soil structure and dung quality and could be important factors that alter dung beetle assemblages in terms of composition, abundance, and biomass on traditional farms.

The Endangered Species Act of 1973 has served as the defacto biodiversity policy in the United States; however, heavy-handed implementation early in the act's history led private landowners to avoid managing land to benefit endangered species. By reducing costs and increasing benefits to landowners, voluntary incentive programs (VIPs) potentially bridge the gap between a policy that discourages beneficial land management on private lands and the need to enhance recovery efforts. However, the effectiveness of VIPs is bound to landowner participation. With the use of a sample of rangeland landowners in central Texas, we examined the potential for private landowners to enroll in an incentive program to protect and maintain habitat for endangered songbirds. First, we characterized landowners based on the centrality of production-oriented agriculture to their lifestyle. This measure of lifestyle centrality was comprised of self-identification as a rancher/farmer, dependence on land for income, and rootedness to the land. Second, we examined the relationship between lifestyle centrality, attitude, and participation in a VIP. With the use of structural-equation modeling, we found attitude toward enrolling mediated the relationship between centrality and a landowner's intention to enroll in a VIP. In addition to demographic analyses, social variables such as attitudes, beliefs, and motivations are needed to understand fully the multiple underlying reasons for participation and nonparticipation in a VIP and to design effective interventions to enhance participation.

Invasion of exotic grasses into grasslands dominated by native plants changes fire cycles and reduces biodiversity. Brush management practices that create soil disturbance, such as aeration, may potentially result in invasion of exotic grasses and replacement of native vegetation. We tested the hypothesis that a long-term effect of aeration and prescribed burning is an increase in exotic grasses. The study was conducted at the Chaparral Wildlife Management Area in the western south Texas plains where four treatments were evaluated: aeration, warm-season burn, aeration followed by a warm-season burn, and no treatment (control). The experimental design was a randomized complete block with four replicates. We estimated percentage canopy cover of exotic grasses, native grasses, forbs, litter, bare ground, and woody and succulent plants in 2007. There was a multivariate main effect among treatments for the dependent variables absolute canopy cover of exotic grasses, native grasses, forbs, litter, and bare ground (Wilks's Lambda F_15,179.84  =  2.78, P  =  0.001). Variables that contributed to the significant overall effect included litter (F_3,69  =  4.32, P  =  0.008) and native grasses (F_3,69  =  6.11, P  =  0.001). The multivariate main effect of treatment was significant (Wilks's Lambda F_9,180.25  =  2.04, P  =  0.038) for the relative canopy cover of herbaceous species. Relative cover of exotic grasses was 31% higher (P  =  0.024) in control than in the prescribed burn treatment. Native grasses relative cover was 30% higher (P  =  0.003) in prescribed burn than in the control treatment. We did not detect differences among treatments in the percentage of total woody and succulent plants canopy cover (P  =  0.083). Under the environmental conditions at the time of the study, aeration and/or prescribed burning do not increase exotic grasses.

Plant-soil variation related to perennial-plant resource islands (coppices) interspersed with relatively bare interspaces is a major source of heterogeneity in desert rangelands. Our objective was to determine how native and exotic grasses vary on coppice mounds and interspaces (microsites) in unburned and burned sites and underlying factors that contribute to the variation in sagebrush-steppe rangelands of the Idaho National Lab, where interspaces typically have abiotic crusts. We asked how the exotic cheatgrass (Bromus tectorum L.) and native bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Löve) were distributed among the microsites and measured their abundances in three replicate wildfires and nearby unburned areas. We conducted a common-garden study in which soil cores from each burned microsite type were planted with seed of either species to determine microsite effects on establishment and growth of native and exotic grasses. We assessed soil physical properties in the common-garden study to determine the intrinsic properties of each microsite surface and the retention of microsite soil differences following transfer of soils to the garden, to plant growth, and to wetting/drying cycles. In the field study, only bluebunch wheatgrass density was greater on coppice mounds than interspaces, in both unburned and burned areas. In the common-garden experiment, there were microsite differences in soil physical properties, particularly in crust hardness and its relationship to moisture, but soil properties were unaffected by plant growth. Also in the experiment, both species had equal densities yet greater dry mass production on coppice-mound soils compared to interspace soils, suggesting microsite differences in growth but not establishment (likely related to crust weakening resulting from watering). Coppice-interspace patterning and specifically native-herb recovery on coppices is likely important for postfire resistance of this rangeland to cheatgrass.

As wildland fire frequency increases around the globe, a better understanding of the patterns of plant community recovery in burned landscapes is needed to improve rehabilitation efforts. We measured establishment of seeded species, colonization of Bromus tectorum and other nonnative annual plants, and recovery of nonseeded native species in topographically distinct areas within five fires that burned Great Basin shrub-steppe communities in Elko County, Nevada. Plant density, frequency, and cover data were collected annually for 4 yr postfire. Vegetation composition varied among flat areas and north- and south-facing aspects, and changed over the course of the sampling period; recovery varied among sites. In general, B. tectorum densities were higher on south aspects, particularly 3 and 4 yr after fire, when densities increased dramatically relative to prefire conditions. Nonseeded native perennial grasses, forbs, and shrubs were abundant in three of the five fire sites, and were more likely to be present on north aspects and flat areas. Over time, nonseeded perennial grass densities remained relatively constant, and nonseeded forbs and shrubs increased. Seeded species were most likely to establish in flat areas, and the density of seeded perennial grasses, forbs, and shrubs decreased over time. Frequency and density measurements were highly correlated, especially for perennial species. Our results emphasize the value of considering site aspect and the potential for native regrowth when planning and monitoring restorations. For example, effective rehabilitation of south aspects may require the development of new restoration methods, whereas north aspects and flat areas in sites with a strong native component were not improved by the addition of seeded species, and may require weed control treatments, rather than reseeding, to improve recovery. Tailoring revegetation objectives, seed mixes, seeding rates, and monitoring efforts to conditions that vary within sites may lead to more cost effective and successful restoration.

Soil water repellency can limit postfire reseeding efforts and thus increase the susceptibility of a site to weed invasion. We evaluated the effectiveness of wetting agents and simulated anchor chaining for improving seedling growth and survival in water-repellent soil, for the native perennial bluebunch wheatgrass (Pseudoroegneria spicata) and invasive annual cheatgrass (Bromus tectorum). Research was performed in a glasshouse, on 20-cm-diameter soil cores that were excavated from underneath burned Utah juniper (Juniperus osteosperma) trees. The experiment was arranged as a randomized split-plot design, with the two grass species sown separately under four soil treatments: 1) no treatment (control), 2) simulated anchor chaining (hereafter referred to as “till”), 3) wetting agent, and 4) till plus wetting agent. Soil water content was highest in the wetting agent treatment, lower for till, and lowest in the control. Overall, the response of bluebunch wheatgrass and cheatgrass was similar among treatments. At the conclusion of the study, wetting agent cores had twice as many seedlings as the control, while the till and control were similar. Despite a lower number of seedlings, tilling in general resulted in the same level of biomass as the wetting agent treatment. Overall, biomass in the till and wetting agent treatments was at least twofold higher than the control. No benefit was found in applying both till and wetting agent treatments together in comparison to just applying wetting agent. Because of a lack of correlation between glasshouse and field settings the results of this study need to be interpreted with caution. Our data may indicate that if cheatgrass is not already present on the site, anchor chaining or treating the soil with wetting agent can increase establishment of seeded species.

There is increasing interest in using canopy area to quantify biomass of invasive woody plants on large land areas of rangelands for a variety of reasons. For those woody species that emphasize lateral canopy growth over vertical growth it may be possible to relate canopy area to aboveground mass (AGM). Our objective was to determine the utility of external canopy measurements (area, volume, and height) for predicting AGM and the percentage of AGM that is wood (PW; i.e., stems > 3 cm diameter) in individual redberry juniper (Juniperus pinchotii Sudw.) plants in west Texas. The canopy area to height relationship was curvilinear and indicated that at heights > 3 m, there was more lateral (canopy area) than vertical canopy growth. We found a strong linear relationship between canopy area and AGM (r²  =  0.94; AGM range 9 kg to 688 kg) and it appeared that AGM could be predicted in individual trees from canopy area. Moreover, the canopy area/AGM relationship developed from smaller trees was able to adequately predict AGM of larger trees. Height was a less effective predictor of AGM (r²  =  0.66), and incorporation of height with canopy area to determine canopy volume did little to improve accuracy of estimating AGM over canopy area alone. The canopy area/PW relationship was curvilinear (the rate of increase in PW declined in larger trees) and PW reached 60–70% in the largest trees.

The amount and distribution of gaps in vegetation canopy is a useful indicator of multiple ecosystem processes and functions. In this paper, we describe a semiautomated approach for estimating canopy-gap size distributions in rangelands from high-resolution (HR) digital images using image interpretation by observers and statistical image classification techniques. We considered two different classification methods (maximum-likelihood classification and logistic regression) and both pixel-based and object-based approaches to estimate canopy-gap size distributions from 2- to 3-cm resolution UltraCamX color infrared aerial photographs for arid and semiarid shrub sites in Idaho, Nevada, and New Mexico. We compare our image-based estimates to field-based measurements for the study sites. Generally, percent of input points correctly classified and kappa coefficients of agreement for plot image classifications was very high. Plots with low kappa values yielded canopy gap estimates that were very different from field-based estimates. We found a strong relationship (R² > 0.9 for all four methods evaluated) between image- and field-based estimates of the total percent of the plot in canopy gaps greater than 50 cm for plots with a classification kappa of greater than 0.5. Performance of the remote sensing techniques varied for small canopy gaps (25 to 50 cm) but were very similar for moderate (50 to 200 cm) and large (> 200 cm) canopy gaps. Our results demonstrate that canopy-gap size distributions can be reliably estimated from HR imagery in a variety of plant community types. Additionally, we suggest that classification goodness-of-fit measures are a potentially useful tool for identifying and screening out plots where precision of estimates from imagery may be low. We conclude that classification of HR imagery based on observer-interpreted training points and image classification is a viable technique for estimating canopy gap size distributions. Our results are consistent with other research that has looked at the ability to derive monitoring indicators from HR imagery.

Leaf area index (LAI) is defined as the one-sided area of leaves above a unit area of ground. It is a fundamental ecosystem parameter that is a required input of process-based plant growth and biogeochemical models. Direct measurement of LAI is the most accurate method, but is destructive, time-consuming, and labor-intensive. LAI is highly variable in time and space on sagebrush-steppe rangelands, and a rapid, nondestructive method is desirable to understand ecosystem processes. The point-intercept method is nondestructive and has been demonstrated to provide accurate LAI estimates, but the method is time-consuming. LAI measurement with the Accupar ceptometer (Decagon Devices, Pullman, WA) is nondestructive and faster than the point-intercept method, but has not been evaluated on sagebrush-steppe rangelands. The objective of this study was to evaluate the ceptometer for measurement of LAI in sagebrush-steppe rangelands. Ceptometer and point-intercept LAI data were collected at six sites in sagebrush-steppe rangelands and the values were compared. We found that 1) ceptometer LAI data were consistently greater than point-intercept LAI data, 2) ceptometer data were much more variable than the point-intercept data based on standard deviations, and 3) the overall correlation between the two methods was very weak (r²  =  0.15). The much greater ceptometer LAI values were, at least partly, due to the large woody component of the vegetative cover. We attribute the high variability of ceptometer-measured LAI to high instrument sensitivity of the angle of the instrument relative to the sun.