@article {JRN55373,
	title = {Mechanisms and drivers of alternative shrubland states},
	journal = {Ecosphere},
	volume = {13},
	year = {2022},
	month = {03 April 2022},
	pages = {e3987},
	abstract = {Grassland-to-shrubland state change has been widespread in arid lands globally. Long-term records at the Jornada Basin USDA-LTER site in the North American Chihuahuan Desert document the time series of transition from grassland dominance in the 1850s to shrubland dominance in the 1990s. This broadscale change ostensibly resulted from livestock overgrazing in conjunction with periodic drought and represents the classic {\textquotedblleft}grassland-to-shrubland{\textquotedblright} regime shift. However, finer-scale observations reveal a more nuanced view of this state change that includes transitions from dominance by one shrub functional type to another (e.g., based on leaf habit [evergreen vs. deciduous], N2 fixation potential, and drought tolerance). We analyzed the Jornada Basin historic vegetation data using a fine-scale grid and classified the dominant vegetation in the resulting 890 cells on each of four dates (1858, 1915, 1928, and 1998). This analysis allowed us to quantify on contrasting soil geomorphic units the rate and spatial distribution of: (1) state change from grasslands to shrublands across the Jornada Basin, (2) transitions between shrub functional groups, and (3) transitions from shrub-to-grass dominance. Results from our spatially explicit, decadal timescale perspective show that: (1) shrubland ecosystems developing on former grasslands were spatially and temporally more dynamic than has been generally presumed, (2) in some locations, shrublands initially developing on grasslands subsequently transitioned to ecosystems dominated by a different shrub functional type, with these changes in shrub composition likely involving changes in soil properties, and (3) some shrub-dominated locations have reverted to grass dominance. Accordingly, traditional, broad characterizations of {\textquotedblleft}grassland-to-shrubland{\textquotedblright} state change may be too simplistic. An accounting of these complexities and transitions from one shrub functional group to another is important for projecting state change consequences for ecosystem processes. Understanding the mechanisms, drivers, and influence of interactions between patterns and processes on transitions between shrub states defined by woody plant functional types will be germane to predicting future landscape change.},
	keywords = {desertification, drylands, plant functional types, regime shifts, shrub growth form, shrubland transitions, Special Feature: Dynamic Deserts},
	doi = {10.1002/ecs2.3987},
	url = {files/bibliography/22-005.pdf},
	author = {Steven R. Archer and Debra C. Peters and N. Dylan Burruss and Jin Yao}
}
@article {JRN54143,
	title = {Beyond desertification: new paradigms for dryland landscapes},
	journal = {Frontiers in Ecology and the Environment},
	volume = {13},
	year = {2015},
	month = {02/2015},
	pages = {4-12},
	chapter = {4},
	abstract = {<p class="rtejustify">The traditional desertification paradigm focuses on the losses of ecosystem services that typically occur when grasslands transition to systems dominated by bare (unvegetated) ground or by woody plants that are unpalatable to domestic livestock. However, recent studies reveal complex transitions across a range of environmental conditions and socioeconomic contexts. The papers in this Special Issue illustrate how an improved understanding of these dynamics is generating more robust paradigms, where state changes and regime shifts occurring within the context of changes in land use and climate are modified by landform and antecedent conditions. New and emerging technologies are being used to characterize and evaluate processes and outcomes across various scales and levels of organization. At the same time, developments in education are taking advantage of these new perspectives to improve the ecological literacy of future generations, and to better inform land-management decisions. A framework that integrates these perspectives provides a more comprehensive approach for understanding and predicting dryland dynamics.</p>
},
	keywords = {desertification, desertification paradigm, dryland landscapes, ecological literacy, ecosystem services, land management, land use, regime shifts, spatial connectivity},
	doi = {10.1890/140276},
	url = {/files/bibliography/15-001.pdf},
	author = {Debra C. Peters and Kris Havstad and Steven R. Archer and O. E. Sala}
}
@article {49871,
	title = {Empirical assessment of state-and-transition models with a long-term vegetation record from the Sonoran Desert},
	journal = {Ecological Applications},
	volume = {22},
	year = {2012},
	month = {03/2012},
	pages = {400-411},
	chapter = {400},
	abstract = {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\&ndash;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\&ndash;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\&rsquo;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.},
	keywords = {alternative stable states, cluster analysis, detrended corrrespondence analysis, dynamic regimes, nonequilibrium theory, rangeland management, regime shifts, thresholds},
	url = {/files/bibliography/12-021.pdf},
	author = {Bagchi, Sumanta and D.D. Briske and X. Ben Wu and M.P. McClaran and Brandon T Bestelmeyer and Maria Fern{\'a}ndez-Gim{\'e}nez}
}
@article {49931,
	title = {Analysis of abrupt transitions in ecological systems},
	journal = {Ecosphere},
	volume = {2},
	year = {2011},
	month = {12/2011},
	pages = {1-26},
	type = {Article 129},
	chapter = {1},
	abstract = {<p>The occurrence and causes of abrupt transitions, thresholds, or regime shifts between ecosystem states are of great concern and the likelihood of such transitions is increasing for many ecological systems. General understanding of abrupt transitions has been advanced by theory, but hindered by the lack of a common, accessible, and data-driven approach to characterizing them. We apply such an approach to 30 \&ndash; 60 years of data on environmental drivers, biological responses, and associated evidence from pelagic ocean, coastal benthic, polar marine, and semi-arid grassland ecosystems. Our analyses revealed one case in which the response (krill abundance) linearly tracked abrupt changes in the driver (Pacific Decadal Oscillation), but abrupt transitions detected in the three other cases (sea cucumber abundance, penguin abundance, and perennial grass production) exhibited hysteretic relationships with drivers (wave intensity, sea-ice duration, and amounts of monsoonal rainfall, respectively) through a variety of response mechanisms. The use of a common approach across these case studies illustrates that: the utility of leading indicators is often limited and can depend on the abruptness of a transition relative to the lifespan of responsive organisms and observation intervals; information on spatiotemporal context is useful for comparing transitions; and ancillary information from associated experiments and observations informs interpretations of response-driver relationships. The understanding of abrupt transitions offered by this approach provides information that can be used to manage state changes and underscores the utility of long-term observations in multiple sentinel sites across a variety of ecosystems.</p>
},
	keywords = {alternative states, Bouteloua eriopoda, desert grassland, krill, leading indicators, Nyctiphanes simplex, Pachythyone rubra, Penguins, Pygoscelis, regime shifts, sea cucumbers, thresholds},
	doi = {10.1890/ES11-00216.1},
	url = {/files/bibliography/11-036.pdf},
	author = {Brandon T Bestelmeyer and Ellison, Aaron M. and William R. Fraser and Gorman, Kristen B. and Sally J. Holbrook and C. Laney and Mark D. Ohman and Debra C. Peters and Pillsbury, Finn C. and Andrew Rassweiler and Russell J. Schmitt and Sharma, Sapna}
}
@conference {50122,
	title = {Preventing regime shifts on the Colorado Plateau: Application of ecological theshold concepts to land management decision making},
	booktitle = {Ecological Society of America Abstracts},
	year = {2009},
	month = {August 2009},
	pages = {PS 48-80},
	abstract = {Investigating the mechanisms responsible for ecological thresholds is essential to understanding processes leading to ecosystem regime shifts. Dryland ecosystems are especially prone to threshold behavior wherein stressor-mediated alteration of patterns and processes can shift systems to alternative states resulting in compromised ecosystem services (e.g., maintenance of biological diversity and soil stability). Despite wide acceptance of the concept, few studies have used or quantified ecological thresholds for direct application to land management. By understanding and quantifying indicators of threshold behavior, land managers may be able to predict an ensuing threshold crossing and implement management actions to prevent a transition to persistent degraded conditions. We are using a combination of observational and experimental data, conceptual and simulation models, and meta-analyses to explore threshold dynamics across multiple ecological sites in dryland ecosystems of the Colorado Plateau region. A primary objective of this research is to determine indicators which (1) provide early warnings of ecosystem degradation in advance of a threshold crossing and (2) can be practically monitored by land management agencies of the Colorado Plateau region. Key degradational processes characteristic of dryland ecosystems include disturbance of biological soil crusts (BSCs), decreased soil stability and increased erosion, and invasion by nonnative plant species. Based on data from sites experiencing various disturbance intensities, we classified 10 biotic and abiotic degraded "syndromes" indicative of potential thresholds. Several syndromes were observed along axes using multivariate ordination. We detected nonlinear relationships between cover of BSCs and soil stability, with soil stability becoming unstable below thresholds in BSC cover. We used simulation models to understand the consequences of decreasing soil stability, and found wind erosion thresholds depend on interactions between soil stability, vegetation structure, and wind speed. Similarly, results suggest that invasions by nonnative plants and compositional shifts depend on interactions between soil properties, land use, proximity to invader propagules, and climate. These results illustrate that whereas general factors leading to degraded states or syndromes can be identified across regions, knowledge of specific mechanisms of threshold behavior for individual sites requires understanding interactions among multiple biotic and abiotic variables across spatial scales. We suggest that early warning indicators of regime shifts to degraded states must include a multivariate approach to quantifying threshold values for use by land management agencies.},
	keywords = {ecosystem, regime shifts, stressor-mediated, threshold},
	author = {M. Miller and S. L. Garman and Lauver,C.L. and Jayne Belnap and C.D. Allen and Brandon T Bestelmeyer and Jeffrey E. Herrick and D.A. Pyke and Gregory S. Okin and Seth M. Munson}
}
