Over the past century, fire has been widely suppressed in the western Great Plains, in part because of the potential negative effects on forage production for livestock. More recently, interest in the use of prescribed fire in shortgrass steppe has increased because of the potential applications for wildlife management, control of unpalatable plant species, and restoration of historic disturbance regimes. We studied the effects of prescribed burns conducted during late winter on herbaceous production, forage nitrogen content, and plant species composition of shortgrass steppe on the Pawnee National Grassland in northeastern Colorado. Late-winter burns conducted in moderately grazed sites under a wide range of precipitation conditions during 1997-2001 did not negatively affect herbaceous production in either the first or the second postburn growing season. Burning followed by a severe drought in 2002 reduced production by 19% in the second postburn growing season of 2003. Burns temporarily suppressed the abundance of broom snakeweed (Gutierrezia sarothrae) and prickly pear cactus (Opuntia polyacantha) and enhanced forage nitrogen content during May and June of the first postburn growing season. These findings suggest that, except following severe drought, prescribed burns conducted during late winter in grazed shortgrass steppe for objectives unrelated to livestock production can also have neutral or positive consequences for livestock. 

Since European settlement vast areas of the tall tussock grassland dominated by Paspalum quadrifarium Lam. and Paspalum exaltatum J. Presl (‘‘pajonal’’ grassland) in the Flooding Pampa of Argentina were converted to croplands and short grasslands. With the use of Landsat satellite images, we analyzed current (1998-2000) cover and spatial integrity of the pajonal community, and compared it with a vegetation map made 50 yr ago (1956-1960). Six categories of land cover were adopted: crops, sown pastures, short grassland, pajonal, wetlands, and anthropogenic areas. With the use of metrics from FRAGSTATS, landscape pattern and composition were analyzed at two scales: 1) regionally, by comparing two edaphic domain areas with relatively low and high restrictions for agriculture (low-restriction domain [LRD] and high-restriction domain [HRD], respectively); and 2) at landscape scale, by comparing ten 22 500-ha randomly selected areas (landscapes) within each edaphic domain. Current relative cover of pajonal grassland (2 173 600 ha) was 32.5%, and similar values were obtained within each edaphic domain. However, the number of pajonal patches was higher and their mean patch size, the Euclidean nearest-neighbor distance among patches (degree of isolation), and their border regularity were lower in the LRD than in the HRD. At landscape scale, the mean size of pajonal patches diminished with the percent of agricultural land within both edaphic domains. The isolation among pajonal patches increased with percent of agricultural land in the HRD, whereas no relationship between the isolation of pajonal patches and percent of agriculture was found in the LRD. As suggested by comparison with past vegetation, current pajonal status mostly results from replacement of pajonal grassland by short grassland types, cultivated pastures, and annual crops (52% and 44% of previously occupied areas in LRD and HRD, respectively), but some expansion of pajonal grassland was also observed (10% and 4% of previously unoccupied areas in LRD and HRD, respectively). 

We assessed the total length of external arbuscular mycorrhizal hyphae as a function of plant species and functional form richness in restored northern tallgrass prairies. Total hyphal length increased with species and functional form richness. Hyphal length also increased when plant communities were dominated by species with high root density, high root to shoot ratios, and high nitrogen use efficiency. Hyphal length was positively correlated with the biomass of late successional C4 grasses (Andropogon gerardi Vitman, Panicum virgatum L., Schizachyrium scoparium [Michx.] Nash-Gould, and Sorghastrum nutans L.), which are obligately mycorrhizal and characterized by high root to shoot ratios, and high root surface area per unit of root biomass. We thus conclude that in order to recover extraradical arbuscular mycorrhizal hyphal length in restored northern tallgrass prairies, at least three factors need to be given priority: 1) achieving high levels of species and functional form richness; 2) making sure that late successional C4 grasses are present; and 3) making sure that the seed mixture includes species that are characterized by high root to shoot ratio, high root density, and high nitrogen-use efficiency. 

This study evaluated the impact of shrub encroachment within cool-season floodplain meadows in a portion of the Rocky Mountain Forest Reserve in southwestern Alberta, where nearly half of open grasslands have been lost since 1958. Sample transects situated in meadows, known formerly to be in open grassland, were assessed in 2001 (n = 21) and 2002 (n = 33) in areas ranging from 0% to 92% shrub cover. Shrub cover, density, and height were correlated to understory parameters, including herbaceous production, bunchgrass cover and density, and species richness and diversity. Additional data on soil horizon depths were obtained. Analysis was conducted using regression to assess empirical relationships between understory or soil characteristics and the overstory. Stronger empirical relationships (i.e., greater R2) were found in 2002, coincident with larger sample sizes and greater rainfall. Among independent overstory variables, aggregate shrub cover for all species accounted for the greatest variation in understory characteristics. Significant (P < 0.01) negative nonlinear relationships were observed between shrub cover and herbage production, with the latter declining from 6 629 kg ha-1 in meadows containing less than 12% shrub cover, to 2 797 kg ha-1 in areas where shrub cover exceeded 35%. Negative linear trends were found (P<0.01) for bunchgrass density and cover in relation to increasing shrub abundance in 2002. Understory diversity increased with shrub abundance, peaking at 64% shrub cover in 2002. Meadows with low and high shrub cover also coincided with thicker Ah and litter, fibric, and humic soil layer (LFH) horizons, respectively. Collectively, these results indicate shrub encroachment is threatening the sustainability of native bunchgrass communities and reducing forage availability. Meadow conservation in this area will require proactive management to protect or restore open grasslands. 

Private landowners are often de facto stewards of biodiversity and ecosystem services. In California’s Sierra Nevada foothills, ranchers frequently present the only defense against biological invasions in private rangelands. Although ranchers’ land management goals (e.g., the desire to control invasive species) can be consistent with ecosystem protection, practical constraints often limit their success. Considerable research on the invasive weed, yellow starthistle (Centaurea solstitialis L.), has produced numerous control strategies. Nevertheless, the range of this noxious weed continues to increase. We used surveys and interviews to document the weed control efforts of 202 ranchers and to identify practical limitations to their efficacy. Overall, 86% of ranchers who had experienced yellow starthistle infestation had attempted control, using one or more of 19 methods. Early response reduced negative effects from yellow starthistle. Control methods learned from agricultural advisors were reported more effective than those learned elsewhere. Limitations to yellow starthistle control in our study population resulted from incomplete information regarding control methods, complexity of weed control in heterogeneous landscapes, inconsistent application of methods, and lack of long-term planning for weed control. Such hindrances make it difficult for landowners to implement control methods promoted by researchers. This gap between science and practice contributes to the continued increase of yellow starthistle within the study region. To shrink this gap, researchers and agricultural advisors can incorporate environmental heterogeneity into applied agricultural research, use land stewards’ knowledge and experience, and increase public education. 

Interpretation of assessment and monitoring data requires information about how reference conditions and ecological resilience vary in space and time. Reference conditions used as benchmarks are often specified via potential-based land classifications (e.g., ecological sites) that describe the plant communities potentially observed in an area based on soil and climate. State-and-transition models (STMs) coupled to ecological sites specify indicators of ecological resilience and thresholds. Although general concepts surrounding STMs and ecological sites have received increasing attention, strategies to apply and quantify these concepts have not. In this paper, we outline concepts and a practical approach to potential-based land classification and STM development. Quantification emphasizes inventory techniques readily available to natural resource professionals that reveal processes interacting across spatial scales. We recommend a sequence of eight steps for the co-development of ecological sites and STMs, including 1) creation of initial concepts based on literature and workshops; 2) extensive, low-intensity traverses to refine initial concepts and to plan inventory; 3) development of a spatial hierarchy for sampling based on climate, geomorphology, and soils; 4) stratified medium-intensity inventory of plant communities and soils across a broad extent and with large sample sizes; 5) storage of plant and soil data in a single database; 6) model-building and analysis of inventory data to test initial concepts; 7) support and/ or refinement of concepts; and 8) high-intensity characterization and monitoring of states. We offer a simple example of how data assembled via our sequence are used to refine ecological site classes and STMs. The linkage of inventory to expert knowledge and site-based mechanistic experiments and monitoring provides a powerful means for specifying management hypotheses and, ultimately, promoting resilience in grassland, shrubland, savanna, and forest ecosystems.