A multi-scale classification of vegetation dynamics in arid lands: What is the right scale for models, monitoring, and restoration?

Measurements of vegetation and soil dynamics used to anticipate (or reverse) catastrophic transitions in arid and semi-arid rangelands are often difficult to interpret. This situation is due, in part, to a lack of empirically based conceptual models that incorporate the effects of multiple processes, scale, spatio-temporal pattern, and soils. Using observations of multitemporal data from the Chihuahuan Desert, we describe a new approach to classifying vegetation dynamics based on multiple scales of vegetation and soil pattern as well as crossscale interactions. We propose the existence of six types of mechanisms driving vegetation change including (1) stability, (2) size oscillation of plants, (3) loss and reestablishment of plants within functional groups, (4) loss of one plant functional group and replacement by another, (5) spatial reorganization of vegetation patches, and (6) cascading transitions that spread from small to broad scales. We provide evidence for the existence of these mechanisms, the species involved, and the geomorphic components on which they are observed in the Chihuahuan Desert. These mechanisms highlight the kinds of multi-scale observations that are needed to detect or interpret change and emphasize the importance of soil surface properties for interpreting vegetation change. The classification is potentially general across arid and semi-arid ecosystems and links spatial and temporal patterns in vegetation with ecological and geomorphic processes, monitoring, and restoration strategies

Effect of Climoedaphic Heterogeneity on Woody Plant Dominance in the Argentine Caldenal Region

Woody plant encroachment is widespread throughout drylands of the world, but rates and patterns of encroachment at the regional scale can be mediated by soil and climate. Climoedaphic properties may therefore help to explain patterns of woody plant dominance. In the Caldenal region of central Argentina, which is experiencing widespread woody plant encroachment, we used stratified and targeted inventory of vegetation and soils alongside climate data to classify vegetation states and then identify factors indicating resistance to woody plant encroachment. We found that three climoedaphic contexts differed in the degree of woody plant dominance. Sandsheet landforms had the lowest likelihood of a shrub thicket state. Within loamy soils, sites with deep soil carbonates in warmer and wetter climates were less likely to feature a shrub thicket state than sites with shallow carbonates in cooler and drier climates. These contexts serve as a basis for recognizing different ecological sites to assist mapping and prioritization of management interventions in the Caldenal region. Simple inventory-based approaches can be helpful for designing land management recommendations in other ecosystems

Effects of managed fire on a swale grassland in the Chihuahuan Desert

Fire is considered a critical process for limiting shrub encroachment and maintaining grassland structure and functions. •Fire can be detrimental to grasses in upland settings of arid desert grasslands, but no studies have been performed in more productive swale grasslands. Monitoring of a prescribed fire treatment in a swale grassland in southern New Mexico indicated that perennial grasses had not recovered after 5 years, even with above-average rainfall. Furthermore, indicators of erosion susceptibility increased, and shrubs resprouted rapidly.The Rangelands archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information

Vulnerability and triggers in the threshold development: models from the Chihuahuan desert

We review models developed for the Draw and Loamy ecological sites in Major Land Resource Area 42.2 in southwestern New Mexico and review empirical support obtained for parts of the model. We describe evidence for 1) vulnerability to transitions and associated triggers and 2) the characteristics of alternative states. Remote-sensing based evidence supports the notion that fragmentation of grass cover creates vulnerability to transition, and anecdotal evidence supports the notion that high intensity storms serve as triggers that initiate erosion and gully formation. Field measurements indicate that degradation of soil structure, increased run-off, and reduced water infiltration are important feedbacks components driving the transition and reinforcing state changes. These relationships are strongly mediated by soil horizon development differences within the ecological site. The state-and-transition model thus links these scientific studies and provides indicators that can be used by managers to gauge the likelihood of threshold development

The effect of small mammal exclusion on grassland recovery from disturbance in the Chihuahuan Desert

In many arid ecosystems, shrub encroachment is coupled to the loss of perennial grasses and associated ecosystem services. Increased native herbivore abundance associated with shrub encroachment can have negative effects on grass restoration. In the Chihuahuan Desert, native herbivore abundance can be two times greater in shrubland states dominated by Prosopis glandulosa (honey mesquite) than in historical Bouteloua eriopoda (black grama) grasslands. We compared the recovery of B. eriopoda patches following disturbance in plots that were exposed to or protected from native herbivores in shrub-dominated, grass-dominated and ecotone (grass and shrub co-dominated) states. We created a disturbance in the center of B. eriopoda grass patches in each treatment quadrat in 2001. The disturbed areas were measured for recruitment and re-establishment of B. eriopoda in 2002, 2005 and 2008. Although mean rodent abundance was generally greater in shrub-dominated states than other states over the study period, reproductive potential of B. eriopoda was similar in shrub and grass dominated states. Additionally, there was no revegetation by B. eriopoda in any state in response to rodent exclusion. Because increased herbivore abundance in shrub-dominated states did not constrain grass revegetation, other factors are likely to be more important constraints on perennial grass recovery in the Chihuahuan Desert

Erratum to “Collaborative Approaches to Strengthen the Role of Science in Rangeland Conservation” [Rangelands 41 (5) (2019) 218–226] (Rangelands (2019) 41(5) (218–226), (S0190052819300227), (10.1016/j.rala.2019.08.001))

The publisher regrets that the keywords and last paragraph of the Introduction contained errors. The corrected keywords and Introduction are shown below. Keywords: Monitoring, Collaborative adaptive management, Brush management, Ecological sites, State transition models Last paragraph of the Introduction should read: In this article, we argue that collaborative science at the landscape scale, supported by developing technologies and stable funding, can mobilize science to improve conservation practice effectiveness. We briefly review the history of science's role in rangeland conservation to provide a background. Then we introduce the Restore New Mexico (RNM) Collaborative Monitoring Program in which we have been applying collaborative science, involving 6 million acres of the Chihuahuan Desert of southwestern New Mexico, for the past 10 years. We review steps we have used in the collaborative science process and how we are applying them in the RNM program. Our ideas presented here draw from and parallel those of an increasingly rich body of collaborative science examples.3–6 The publisher would like to apologise for any inconvenience caused. © 2020The Rangelands archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information

Collaborative Approaches to Strengthen the Role of Science in Rangeland Conservation

The use of science to inform conservation practices is limited by broad generalities generated from limited sampling alongside narrow ecosystem service perspectives. Collaborative science approaches featuring “social-ecological system” perspectives are being used as a means to improve the utility of science. We review our approach to collaborative science to improve brush management outcomes in rangelands in the Chihuahuan Desert. Expanding the use and utility of collaborative science requires stable support via targeted funding and technical expertise, as well as web-based tools and mobile applications that link specific locations to science information and conservation practice guidelines.The Rangelands archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information

Threshold changes in vegetation along a grazing gradient in Mongolian rangelands

1.The concept of threshold has become important in ecology, but the nature of potential threshold responses of vegetation to grazing in rangeland ecosystems remains poorly understood. We aimed to identify ecological thresholds in vegetation changes along a grazing gradient and to examine whether threshold changes were expressed similarly at a variety of ecological sites. 2. To accomplish this, we surveyed the vegetation along grazing gradients at 10 ecological sites, each located at different landscape positions in Mongolia's central and southern rangelands. Evidence for a threshold in changes in floristic composition along the grazing gradient was examined by comparing linear models of the data with nonlinear models fitted using an exponential curve, an inverse curve, a piecewise regression and a sigmoid logistic curve. 3. Three nonlinear models (piecewise, exponential and sigmoid) provided a much better fit to the data than the linear models, highlighting the presence of a discontinuity in vegetation changes along the grazing gradient. The shapes of the best-fit models and their fit to the data were generally similar across sites, indicating that the changes in floristic composition were relatively constant below a threshold level of grazing, after which the curve changed sharply. 4. Except for two sites, the best-fit models had relatively narrow bootstrap confidence intervals (95% CI), especially around threshold points or zones where the rate of change accelerated, emphasizing that our results were robust and conclusive. 5. Synthesis. Our study provided strong evidence for the existence of ecological thresholds in vegetation change along a grazing gradient across all ecological sites. This suggests that vegetation responses to grazing in the study areas are essentially nonlinear. The recognition that real threshold changes exist in real grazing gradients will help land managers to prevent the occurrence of undesirable states and promote the occurrence of desirable states, and will therefore permit a major step forward in the sustainable management of rangeland ecosystems