|BRISKE, DAVID - Texas A&M University
Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/5/2012
Publication Date: 11/1/2012
Citation: Bestelmeyer, B.T., Briske, D.D. 2012. Grand challenges for resilience-based management of rangelands. Rangeland Ecology and Management. 65:654-663.
Interpretive Summary: Resilience-based frameworks, including state-and-transition models (STM), are being increasingly called upon to inform policy and guide ecosystem management, particularly in rangelands. Yet, multiple challenges impede their effective implementation: (1) paucity of empirical tests of resilience concepts, such as alternative states and thresholds, and (2) heavy reliance on expert models, which are seldom tested against empirical data. We developed an analytical protocol to identify unique plant communities and their transitions, and applied it to a long-term vegetation record from the Sonoran Desert (1953–2009). We assessed whether empirical trends were consistent with resilience concepts, and evaluated how they may inform the construction and interpretation of expert STMs. Seven statistically distinct plant communities were identified based on the cover of 22 plant species in 68 permanent transects. We recorded 253 instances of community transitions, associated with changes in species composition between successive samplings. Expectedly, transitions were more frequent among proximate communities with similar species pools than among distant communities. But unexpectedly, communities and transitions were not strongly constrained by soil type and topography. Only 18 transitions featured disproportionately large compositional turnover (species dissimilarity ranged between 0.54 and 0.68), and these were closely associated with communities that were dominated by the common shrub (burroweed, Haplopappus tenuisecta); indicating that only some, and not all, communities may be prone to large compositional change. Temporal dynamics in individual transects illustrated four general trajectories: stability, nondirectional drift, reversibility, and directional shifts that were not reversed even after 2–3 decades. The frequency of transitions and the accompanying species dissimilarity were both positively correlated with fluctuation in precipitation, indicating that climatic drivers require more attention in STMs. Many features of the expert models, including the number of communities and participant species, were consistent with empirical trends, but expert models underrepresented recent increases in cacti while overemphasizing the introduced Lehmann’s lovegrass (Eragrostis lehmanniana). Quantification of communities and transitions within long-term vegetation records presents several quantitative metrics such as transition frequency, magnitude of accompanying compositional change, presence of unidirectional trajectories, and lack of reversibility within various timescales, which can clarify resilience concepts and inform the construction and interpretation of STMs.
Technical Abstract: The social and ecological contexts for rangeland management are changing rapidly, prompting a reevaluation of science, management, and the linkages between them. Here, we argue that the recent transformation from a steady state to an ecosystem management model has served the rangeland profession well, but that further transformation to resilience-based management is required to ensure that rangeland services will continue to benefit society in an era of rapid change. Resilience-based management emphasizes collaborative management and social learning to guide adaptation and transformation in social-ecological systems. The objectives of this forum are to: 1) justify the need for adopting resilience-based management, 2) identify the challenges that will be encountered in its development and implementation, and 3) highlight approaches to overcoming these challenges. Five categories of challenges confronting the adoption of resilience-based management, based upon the insights of 55 of rangeland researchers that have contributed to this special issue, were identified as: a) development of knowledge systems to support resilience-based management, b) improvement of ecological models supporting science and management, c) protocols to assess and manage tradeoffs among ecosystem services, d) use of social-ecological system perspectives to achieve greater stakeholder participation, and e) reorganization of institutions to support resilience-based management. It has become clear that greater scientific knowledge by itself is insufficient to promote resilience-based management in rangelands. Resolving the challenges presented here will require the creation of stronger partnerships between ecosystem managers, science organizations, management agencies, and policymakers at local, regional, and national scales. The creation of social learning institutions tied to evolving knowledge systems is our best hope to guide adaptation and transformation in rangelands in the coming century.