The objective of this paper is to recommend conceptual modifications for incorporation in state-and-transition models (STMs) to link this framework explicitly to the concept of ecological resilience. Ecological resilience describes the amount of change or disruption that is required to transform a system from being maintained by one set of mutually reinforcing processes and structures to a different set of processes and structures (e.g., an alternative stable state). In light of this concept, effective ecosystem management must focus on the adoption of management practices and policies that maintain or enhance ecological resilience to prevent stable states from exceeding thresholds. Resilience management does not exclusively focus on identifying thresholds per se, but rather on within-state dynamics that influence state vulnerability or proximity to thresholds. Resilience-based ecosystem management provides greater opportunities to incorporate adaptive management than does threshold-based management because thresholds emphasize limits of state resilience, rather than conditions that determine the probability that these limits will be surpassed. In an effort to further promote resilience-based management, we recommend that the STM framework explicitly describe triggers, at-risk communities, feedback mechanisms, and restoration pathways and develop process-specific indicators that enable managers to identify at-risk plant communities and potential restoration pathways. Two STMs representing different ecological conditions and geographic locations are presented to illustrate the incorporation and application of these recommendations. We anticipate that these recommendations will enable STMs to capture additional ecological information and contribute to improved ecosystem management by focusing attention on the maintenance of state resilience in addition to the anticipation of thresholds. Adoption of these recommendations may promote valuable dialogue between researchers and ecosystem managers regarding the general nature of ecosystem dynamics.

Rangeland scientists struggle with how long rangeland experiments must continue in order to detect treatment effects, particularly in semiarid ecosystems characterized by slow responses and high spatiotemporal variability. We compared changes in eight grass and three shrub categories to grazing systems (yearlong vs. seasonal rotation with equivalent long-term stocking rates), and covariates (precipitation and mesquite [Prosopis velutina] gradients) over 12 yr (1972–1984) and 34 yr (1972–2006) on the Santa Rita Experimental Range, Arizona. We used split-plot analysis of variance, with year as the split, to make these comparisons. Grazing systems did not influence plant dynamics as shown by the lack of grazing system by year effect on all response variables in either time period. The absence of a detectable grazing effect on vegetation changes may be due to overriding influences of grazing intensity, pasture size, precipitation variability, and few replicates. Also, more time may be needed to detect the small accumulating and potentially temporary effects from grazing systems. The grazing system main effects present at the beginning and throughout the study suggest that pastures assigned to each grazing system had different potentials to support vegetation. Nearly twice the number of response variables were related to the precipitation covariate than to mesquite cover, but only about half of all the relationships were consistent between time periods. The struggle to know how long to observe before detecting a grazing system effect was not resolved with the additional 22 yr of observation because we cannot definitively reject that either more time is needed to detect small but cumulative effects or that the two grazing systems are not different.

The claim that intensive rotational grazing (IRG) can sustain higher stocking rates can be partially explained by more even spatial distribution of grazing such that livestock consume forage from a greater proportion of a pasture. To test the hypothesis that utilization is more even at the higher stocking densities of smaller paddocks, mean absolute deviation (heterogeneity) of utilization estimates by plot was compared in paddocks of sizes and stocking densities representing increasing subdivision from two-paddock deferred rotation grazing (DRG) to 16-, 32-, and 64-paddock, two-cycle IRG. These 70-, 4-, 2-, and 1-ha paddocks were grazed for 7 wk, 4 d, 2 d, and 1 d, respectively, at 32 animal unit days (AUD)·ha⁻¹ during 2000 and 34 AUD·ha⁻¹ during 2001. Within IRG there was no response to the treatment gradient. After one cycle in the IRG paddocks, heterogeneity of use was generally lower than in the DRG paddocks, in both 2000 (3–11% [outlier 18%] vs. 14–19%) and 2001 (9–17% vs. 24–28%). After a second cycle in 2001, heterogeneity in half of the IRG paddocks (17–21%) was nearly as high as the early-grazed (24%), but not the late-grazed (28%), of the DRG paddocks. This lack of a stronger difference between systems was probably due to the fixed two-cycle IRG schedule and lack of plant growth during the nongrazing interval. Across both systems heterogeneity of utilization was strongly positively correlated with paddock size. Because utilization was not severely patchy in the largest treatment, the difference between systems would likely be greater in commercial-scale paddocks. Thus grazing distribution can be more even under intensive than extensive management, but this depends on how adaptively the system, particularly the aspects of timing and frequency, is managed.

Forage selection patterns of cattle in sagebrush (Artemisia L.) communities are influenced by a variety of environmental and plant-associated factors. The relative preference of cattle for interspace versus under-sagebrush canopy bunchgrasses has not been documented. Potential preferences may indirectly affect habitat for sage-grouse and other ground-nesting birds. Our objectives were to investigate grazing patterns of cattle with respect to undercanopy (shrub) and interspace tussocks, determine the influence of cattle grazing on screening cover, and relate shrub morphology to undercanopy grazing occurrence. Eighteen-day replicated trials were conducted in the summers of 2003 and 2004. Findings suggest cattle initially concentrate grazing on tussocks between shrubs, and begin foraging on tussocks beneath shrubs as interspace plants are depleted. Grazing of undercanopy grass tussocks was negligible at light-to-moderate utilization levels ( < 40% by weight). Grass tussocks under spreading, umbrella-shaped shrub canopies were less likely (P < 0.001) to be grazed than those beneath erect, narrow canopies. Horizontal screening cover decreased (P < 0.001) with pasture utilization. At the trial's end, removal of 75% of the herbaceous standing crop induced about a 5% decrease in screening cover in all strata from ground level to 1 m with no differences among strata (P = 0.531). This implied that shrubs constituted the majority of screening vegetation. Our data suggest that conservative forage use, approaching 40% by weight, will affect a majority (about 70%) of interspace tussocks and a lesser proportion (about 15%) of potential nest-screening tussocks beneath sagebrush. Probability of grazing of tussocks beneath shrubs, however, is also affected by shrub morphology. These findings will help managers design grazing programs in locales where habitat for ground nesting birds is a concern.

We conducted a study to determine the role of piñon–juniper (PJ) woodland in providing shelter for cattle at a site in central New Mexico. Positions of 16 cows, 8 pregnant or nursing (PN) and 8 nonpregnant–nonlactating (NPNL), grazing a PJ woodland–grass steppe mosaic were recorded every 5 min by Global Positioning System during late winter and early spring in 2004 and 2005 (eight different cows in each year). Hourly weather variables were also recorded at a weather station located at our research site. Weekly fecal samples were collected from all collared cattle (n = 16) to determine botanical composition of diets. Decreasing air temperatures, increasing relative humidity, winds out of the northwest (all of which are associated with heat loss), and increasing short-term thermal stress were associated with a detectable (P ≤ 0.05) increase in PJ-woodland preference of PN and NPNL cows. Days to/from calving date was a significant predictor of PJ-woodland preference of PN cows (P ≤ 0.05), which showed highest PJ-woodland preference on the day before or immediately after calving date. Preference for PJ woodland by all cows, averaged across the study period, increased with the increasing proportion of days with cold short-term thermal stress (P < 0.01) and decreasing availability of open shortgrass forage (P < 0.01). PN and NPNL cows exhibited detectably different grazing patterns (P = 0.01). PN cows explored smaller areas (P < 0.01) and traveled shorter distances (P = 0.053) than NPNL counterparts in any given day. Winterfat (Krascheninnikova lanata [Pursh] A. Meeuse & Smit) was the only plant species analyzed that was detectably more abundant (P = 0.05) in NPNL vs. PN diets, particularly during the week surrounding calving in 2005. Our data suggest that PJ woodland with abundant understory can play an important role in providing shelter for nursing or dry cattle during winter, particularly in years when forage availability is scarce.

Narrowleaf globemallow (Sphaeralcea angustifolia [Cav.] G. Don) occurs on millions of hectares of rangeland in the United States and Mexico, and it constitutes an important forage for herbivores. Forty 2-mo-old crossbred female goats (native×dairy goats; 9.4 ± 2.2 kg) were randomly allotted to five dietary groups (two] goats per pen, four replications per ration) to evaluate the effects of feeding different levels of S. angustifolia in a complete ration on growth performance and diet digestibility. The rations were a total mixed control ration containing 0% S. angustifolia (T0) and four rations in which S. angustifolia progressively replaced alfalfa (25% [T25], 50% [T50], 75% [T75], and 100% [T100]). Grains and forage made up 70% and 30% of the dietary dry matter (DM) in all rations. Differences (P < 0.05) were observed between treatments in average daily gain (ADG; range 88–124 g·d⁻¹) and DM intake (DMI; range 3.3–4.0% body weight). Feed conversion ratio (DMI/ADG; range 4.0–4.8) was similar (P>0.20) among treatments. Goats fed diets with any of the S. angustifolia levels had similar apparent nitrogen (N) digestion (range 67.6–69.8%) as those fed only alfalfa, but N retention was greater (P < 0.05) in goats on T25 and T50 diets compared to other diets. The apparent digestibilities of DM, neutral detergent fiber, and acid detergent fiber were greater (P < 0.05) for T25 and T50 than for other diets. Results indicate that S. angustifolia at the flowering stage was a savory and nutritious roughage, which could fully replace alfalfa hay in diets of growing goats. Considering that S. angustifolia is readily consumed by foraging animals, it is abundant enough that it is a significant source of forage, and has a sufficient quality to nutritionally satisfy herbivores, this forb is a potentially useful forage for pen-fed goats.

Juniper encroachment into otherwise treeless shrub lands and grasslands is one of the most pronounced environmental changes observed in rangelands of western North America in recent decades. Most studies on juniper change are conducted over small areas, although encroachment is occurring throughout regions. Whether changes in juniper cover can be assessed over large areas with the use of long-term satellite data is an important methodological question. A fundamental challenge in using satellite imagery to determine tree abundance in rangelands is that a mix of trees, sagebrush, and herbaceous cover types can occur within a given image pixel. Our objective was to determine if spectral mixture analysis could be used to estimate changes in Rocky Mountain juniper (Juniperus scopulorum Sarg) and Utah juniper (Juniperus osteosperma [Torr.] Little) cover over 20 yr and 20000 ha in southeast Idaho with the use of Landsat imagery. We also examined the spatial patterns and variation of encroachment within our study area using Geographic Information Systems–based data sets of grazing use, land-cover types, and topography. Juniper cover determined from 15-cm-resolution digital aerial orthophotography was used to train and validate juniper presence/absence classification in 1985 and 2005 Landsat images. The two classified images were then compared to detect changes in juniper cover. The estimated rate of juniper encroachment over our study area was 22–30% between 1985 and 2005, consistent with previous ground-based studies. Moran's I analysis indicated that juniper encroachment pattern was spatially random rather than clustered or uniform. Juniper encroachment was significantly greater in grazed areas (P = 0.02), and in particular in grazed shrub land cover type (P = 0.06), compared to ungrazed areas. Juniper encroachment was also greater on intermediate slopes (10–35% slopes) compared to steeper or flatter terrain, and encroachment was somewhat less on north-facing (P = 0.03) and more on west-facing (P = 0.02) slopes compared to other aspects.

Government agencies are subject to increasing public scrutiny of land management practices. Consequently, rigorous, yet efficient, monitoring protocols are needed to provide defensible quantitative data on the status and trends of rangeland vegetation. Rigor requires precise, repeatable measures, whereas efficiency requires the greatest possible information content for the amount of resources spent acquiring the information. We compared two methods—point frequency and visual estimate—of measuring canopy cover of individual plant species and groups of species (forbs vs. graminoids, native vs. nonnative) and plant species richness. These methods were compared in a variety of grassland vegetation types of the northern Great Plains for their precision, repeatability, and efficiency. Absolute precision of estimates was similar, but values generally differed between the two sampling methods. The point-frequency method yielded significantly higher values than the visual-estimate method for cover by individual species, graminoid cover, and total cover, and yielded significantly lower values for broadleaf (forb shrub) cover and species richness. Differences in values derived by different sampling teams using the same method were similar between methods and within precision levels for many variables. Species richness and median species cover were the major exceptions; for these, the point-frequency method was far less repeatable. As performed in this study, the visual-estimate method required approximately twice the time as did the point-frequency method, but the former captured 55% more species. Overall, the visual-estimate method of measuring plant cover was more consistent among observers than anticipated, because of strong training, and captured considerably more species. However, its greater sampling time could reduce the number of samples and, therefore, reduce the statistical power of a sampling design if time is a limiting factor.

Cheatgrass (Bromus tectorum L.) is a winter annual weed that presents a serious obstacle to rangeland restoration in the Intermountain West. The objective of this study was to evaluate factors regulating the size and persistence of cheatgrass carryover seed banks on semiarid sites in western Utah. We prevented current-year seed production in each of four habitats, then tallied emerging seedlings over the next 4 yr. Two iterations of the study were conducted during consecutive years. One year before initiation of each iteration, we estimated seed rain at each site. Above-average precipitation in 1998–1999 resulted in relatively high seed rain (13942 seeds·m⁻²) for the first iteration, whereas seed rain for the second iteration averaged only 3567·m⁻² because of drought conditions in 1999–2000. Mean total number of seedlings emerging from carryover seeds for the first and second iterations were 1304 and 270 seedlings·m⁻². Seedling emergence from carryover seed was positively correlated with production-year seed rain (R² = 0.69). The fraction of seed rain that carried over tended to be lower when precipitation the year following production favored fall emergence of the transient seed bank. First-year emergence of carryover seeds averaged 96% of total emergence, whereas third-year emergence averaged < 1% and was zero for six of eight cases. Carryover seeds persisted somewhat longer at the xeric black greasewood site than at more upland sites. Our study shows that cheatgrass seeds rarely persist beyond the second carryover year even on semiarid sites. Emergence from the carryover seed bank can be predicted from site attributes and precipitation patterns in previous years.

The Ecological Area-wide Management Leafy Spurge, or TEAM Leafy Spurge, began collecting and redistributing flea beetles (Aphthona spp.) to research/demonstration sites and landowners throughout the Little Missouri River drainage basin to control leafy spurge in 1998. A study to evaluate the change over time of leafy spurge (Euphorbia esula L.) phytosociological characteristics following release of flea beetles was initiated in 2002 on leafy spurge–infested pasture and rangeland in the Little Missouri River drainage of Montana, North Dakota, South Dakota, and Wyoming. A total of 292 flea beetle release sites were analyzed in June and July 2002 and 2003 for leafy spurge stem density, foliar cover, flea beetle density, and vegetation composition. Leafy spurge stem density suppression was evident at 91% of the study sites. On two-thirds of the study sites stem density was reduced from greater than 100 stems·m⁻¹ to less than 25 stems·m⁻¹. Leafy spurge foliar cover was less than 5% on approximately two-thirds of the flea beetle release sites and less than 25% on over 90% of the release sites. Area of observed leafy spurge suppression ranged from 0 m² to 30000 m². Approximately 40% of the release sites had leafy spurge suppression ranging from 1000 m² to 5000 m², and 14% of the release sites had greater than 10000 m² of leafy spurge control. Plant community composition following leafy spurge suppression was characteristic of native plant communities that had not been burned or grazed. Flea beetles effectively reduced leafy spurge stem density and cover in 4–5 yr across a variety of locations and corresponding environmental conditions, both within the Little Missouri River drainage and in selected nearby locations.

Astragalus filipes Torr. ex A. Gray (basalt milkvetch or threadstalk milkvetch) is a legume that is widely distributed in western North America and holds promise for revegetation and restoration programs in the western United States. Seed of 67 accessions was collected in 2003 from Utah, Nevada, Idaho, Oregon, California, and Washington. Field-collected forage samples from these accessions had nondetectable or low levels of selenium, swainsonine, and nitrotoxins. Accessions were evaluated at Providence and Millville in northern Utah in 2005 and 2006. At Providence accessions from north-central Oregon exhibited comparatively high biomass yield in summer and fall during both years. Basalt milkvetch accessions with low biomass generally had high crude protein concentration. Acid-detergent fiber and neutral-detergent fiber were positively correlated with biomass yield (r = 0.42, P < 0.0001; r = 0.57, P < 0.0001, respectively). At Millville accessions from north-central Oregon exhibited comparatively high biomass and seed yield. Seed weight per 100 seeds varied among basalt milkvetch accessions in both years at Millville. Plants at Millville treated with imadicloprid insecticide had greater seed yields than nontreated plants in 2006, but not in 2005. When averaged across sites and years, a high correlation between number of stems and biomass (r = 0.82, P < 0.0001) indicated that number of stems is a reliable predictor of high biomass and seed yield. Principal component analysis of seven consolidated plant traits identified two principal components that accounted for 60% and 15% of the variation among accessions. The first principal component was negatively correlated with elevation (r = −0.71, P < 0.01) and positively correlated with latitude (r = 0.46, P < 0.01). The second principal component was positively correlated with elevation (r = 0.36, P < 0.01) and negatively correlated with latitude (r = −0.47, P < 0.01). These results are beneficial in identifying basalt milkvetch accessions that hold promise for plant improvement efforts.

Growing recognition that periodic fire is critical for maintaining the health of many rangeland ecosystems and concerns over more frequent catastrophic wildfires have focused attention on prescribed fire as an ecosystem restoration and fuel management tool. In states such as Texas, where most land is privately owned, the level of success of outreach activities aimed at expanding the adoption of specific management practices is influenced by the extent to which landowners' perceptions, interests, and concerns regarding such practices are addressed. This is particularly important for prescribed fire, which has been perceived by many landowners to be a dangerous or wasteful practice. Here we report the results of a mail survey of 185 members of the Edwards Plateau Prescribed Burn Association (EPPBA) and a random sample of 600 nonmember rural landowners in four counties in the Edwards Plateau and two counties in the Rolling Plains ecoregions of Texas. The overall response rate was 46.6%. Primary reasons respondents did not apply fire on their land were insufficient resources, legal concerns, and lack of assistance with burn plan development. EPPBA members had more positive attitudes than nonmembers about the ecological role of fire and the use of prescribed fire. Our study suggests that adoption of prescribed burning as an integral part of land management plans by private landowners could be expanded by forming new prescribed burning associations. The EPPBA model for such associations provides learning opportunities that are consistent with adult learning and innovation adoption principles. It facilitates fire safety training, reduces concerns over legal liability associated with fire ignition, and enhances access to shared fire management equipment and labor on burn days. The two-tiered structure of the EPPBA with some form of state-level representation appears to be an efficient organizational structure for these associations.