@article {JRN55394, title = {Degradation influences equilibrium and non-equilibrium dynamics in rangelands: Implications in resilience and stability}, journal = {Applied Vegetation Science}, year = {2022}, month = {06/2022}, pages = {e12670}, abstract = {Question: Plant communities are structured by both equilibrium and non-equilibrium dynamics, which interact at different spatio-temporal scales. The influence of external factors on internal regulation processes might depend on ecological state, and thus, on system resilience. We asked if well conserved (reference) states have higher resilience to external factors than degraded states, considering the greater capacity for self-regulation expected of reference states.}, keywords = {Alternative States Amplitude, Elasticity, grazing, Malleability, Rainfall Events, resistance, States and Transitions Model, thresholds}, doi = {10.1111/avsc.12670}, url = {files/bibliography/22-017.pdf}, author = {Dardo Rub{\'e}n L{\'o}pez and Laura Cavallero and Priscila Willems and Brandon T Bestelmeyer and M. A. Brizuela} } @proceedings {JRN55189, title = {Defining thresholds for wind erosion in desert rangeland STMs}, volume = {Session 9}, year = {2020}, month = {02/16/2020}, address = {Denver, CO}, abstract = {

Within the US, conventional understanding has been that most erosion is occurring in the Great Plains, but our knowledge about the extent and severity of rangeland wind erosion has been limited by monitoring and modeling technologies. Data from air quality monitoring programs like IMPROVE show there was a 75\% increase in spingtime fine dust concentrations between 2000 and 2014 across the western states, but we still have a limited understanding of where, when and how much erosion is occurring. Importantly, few tools are available to help managers assess why wind erosion is occurring in responses to land use and management. This information is needed to identify appropriate conservation practices. As a consequence, wind erosion isn{\textquoteright}t typically considered in assessments of land resource condition despite its importance for plant community dynamics, agroecosystem resilience, regional air quality and climate. To address this problem we developed an Aeolian EROsion (AERO) model designed to run on standardized soil and vegetation monitoring datasets that are collected across the west. AERO is a physically-based model that requires inputs of surface soil texture, bare soil fraction, canopy gap size distribution, average canopy height and time-series or probability distribution of wind speeds for a plot location. By leveraging large standardized monitoring datasets, like those collected by the NRCS NRI and BLM AIM programs, AERO can be used to develop an understanding of potential sediment transport rates and dust emissions across rangelands as influenced by soil properties and the kinds, amounts, proportions and structure of different vegetation species. From AERO applications, we are developing approaches based on the Ecological Land Resource Hierarchy to understand the range of potential wind erosion for different land units at different spatial scales. Our work is then exploring approaches to establish benchmarks based on structural and functional thresholds of concern that enable managers to evaluate how wind erosion responds to changes in the kinds, amounts and proportions of vegetation within ecological sites. By using AERO to integrate the indicators of vegetation structure, the model can also be used to identify functional thresholds for wind erosion and assess whether these thresholds can be generalized across ecological sites and states to inform management at broader spatial scales.

}, keywords = {desert rangeland STMs, thresholds, wind erosion}, author = {Nicholas Webb and Brandon Edwards and Rachel Burke and Sarah McCord and Justin Van Zee and Ericha Courtright and Brad Cooper} } @article {JRN54567, title = {Land Ecology Essay II: Thresholds, novel ecosystems, and the sanctity of history}, journal = {Rangelands}, volume = {37}, year = {2015}, month = {12/2015}, pages = {244-246}, chapter = {244}, abstract = {

Dr. Brandon Bestelmeyer is a research ecologist with the USDA Agricultural Research Service{\textquoteright}s Jornada Experimental Range and the Jornada Basin LTER at New Mexico State University in Las Cruces, New Mexico. He regularly writes about rangeland issues on the Land Ecology blog.

To read more of Brandon{\textquoteright}s essays, visit http://landecology.org/.

{\textquotedblleft}Land ecology{\textquotedblright} honors the holistic approach to the knowledge needed to support land stewardship into our increasingly uncertain future. Here we share an expanded version of one of Brandon{\textquoteright}s recent essays.

}, keywords = {Land Ecology, novel ecosystems, Sanctity of History, thresholds}, doi = {10.1016/j.rala.2015.10.009}, url = {/files/bibliography/15-024.pdf}, author = {Brandon T Bestelmeyer} } @article {49836, title = {Assessing resilience and state-transition models with historical records of cheatgrass Bromus tectorum invasion in North American sagebrush-steppe}, journal = {Journal of Applied Ecology}, volume = {50}, year = {2013}, month = {09/2013}, pages = {1131-1141}, chapter = {1131}, abstract = {

1. Resilience-based approaches are increasingly being called upon to inform ecosystem management, particularly in arid and semi-arid regions. This requires management frameworks that can assess ecosystem dynamics, both within and between alternative states, at relevant time scales.

2. We analysed long-term vegetation records from two representative sites in the North American sagebrush-steppe ecosystem, spanning nine decades, to determine if empirical patterns were consistent with resilience theory, and to determine if cheatgrass Bromus tectorum invasion led to thresholds as currently envisioned by expert-based state-and-transition models (STM). These data span the entire history of cheatgrass invasion at these sites and provide a unique opportunity to assess the impacts of biotic invasion on ecosystem resilience.

3. We used univariate and multivariate statistical tools to identify unique plant communities and document the magnitude, frequency and directionality of community transitions through time. Community transitions were characterized by 37{\textendash}47\% dissimilarity in species composition, they were not evenly distributed through time, their frequency was not correlated with precipitation, and they could not be readily attributed to fire or grazing. Instead, at both sites, the majority of community transitions occurred within an 8{\textendash}10 year period of increasing cheatgrass density, became infrequent after cheatgrass density peaked, and thereafter transition frequency declined.

4. Greater cheatgrass density, replacement of native species and indication of asymmetry in community transitions suggest that thresholds may have been exceeded in response to cheatgrass invasion at one site (more arid), but not at the other site (less arid). Asymmetry in the direction of community transitions also identified communities that were {\textquoteleft}at-risk{\textquoteright} of cheatgrass invasion, as well as potential restoration pathways for recovery of pre-invasion states.

cheatgrass, Bromus tectorum, community transitions, dynaimc regime, ecological resilience, ecosystem manasgement, invasive species, rangelands, resilience-based management, thresholds, Artemisia, sagebrush-steppe

5. Synthesis and applications. These results illustrate the complexities associated with threshold identification, and indicate that criteria describing the frequency, magnitude, directionality and temporal scale of community transitions may provide greater insight into resilience theory and its application for ecosystem management. These criteria are likely to vary across biogeographic regions that are susceptible to cheatgrass invasion, and necessitate more in-depth assessments of thresholds and alternative states, than currently available.

}, keywords = {Artemisia, Bromus tectorum, cheatgrass, community transitions, dynaimc regime, ecological resilience, ecosystem manasgement, invasive species, rangelands, resilience-based management, sagebrush-steppe, thresholds}, doi = {10.1111/1365-2664.12128}, url = {/files/bibliography/13-026.pdf}, author = {Bagchi, Sumanta and D.D. Briske and Brandon T Bestelmeyer and X. Ben Wu} } @inbook {49858, title = {Desertification of Rangelands}, booktitle = {Climate Vulnerability: Understanding and Addressing Threats to Essential Resources}, series = {Climate Vulnerability}, volume = {4}, number = {4}, year = {2013}, pages = {239-258}, publisher = {Academic Press}, organization = {Academic Press}, edition = {First}, abstract = {Desertification, the broad-scale conversion of perennial grasslands to dominance by xerophytic shrubs, and the attendant consequences to ecosystem services has affected arid and semiarid regions globally over the past several centuries. This state change is expected to continue in the future as environmental drivers continue to change. It is generally well-recognized that desertification is a cumulative threat that explicitly includes both climatic (e.g., drought) and land-use drivers (e.g., livestock overgrazing and inappropriate conversions of rangeland to cropland).\  However, a basis for ranking the relative importance of these drivers is lacking for many locations. In addition, the emergence of additional drivers (e.g., non-native forbs and grasses modifying historic fire regimes), will result in even more complex dynamics in the future. Clearly, directional changes in climate can have unanticipated effects, in particular for dryland regions with low and variable precipitation and high temperatures in the growing season. However, any change in climate will be operating across diverse landscapes that include a mosaic of human-dominated and natural states, each governed by different drivers and susceptible to different threats. Accounting for the separate and interactive effects of these threats on grassland-shrubland transitions will be necessary as we move forward into a difficult to predict, if not unknown, environmental world.}, keywords = {biodiversity, climate, desertification, dryland ecosystems, feedbacks, grasslands, invasive species, land management, land use, land-atmosphere interactions, shrublands, state change, thresholds, water, wind}, doi = {10.1016/B978-0-12-384703-4.00426-3}, url = {/files/bibliography/13-014.pdf}, author = {Debra C. Peters and Steven R. Archer and Brandon T Bestelmeyer and Brooks, Andrew and Joel R. Brown and Comrie, Andrew and Gimblett, H. Randy and Goldstein, Joshua H. and Kris Havstad and Lopez-Hoffman, L. and Curtis H. Monger and Gregory S. Okin and A. Rango and O. E. Sala and Craig Tweedie and Enrique Vivoni} } @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\–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.}, 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 = {

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 \– 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.

}, 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} } @article {49928, title = {Spatial perspectives in state-and-transition models: A missing link to land management?}, journal = {Journal of Applied Ecology}, volume = {48}, year = {2011}, month = {03/2011}, pages = {746-757}, chapter = {746}, abstract = {Conceptual models of alternative states and thresholds are based largely on observations of ecosystem processes at a few points in space. Because the distribution of alternative states in spatially-structured ecosystems is the result of variations in pattern-process interactions at different scales, we argue that data and models need to explicitly consider ecosystem processes in the context of the spatial pattern of drivers, spatial dependence in responses to drivers, and the spatial structure of feedbacks. Here, we review the literature on spatial patterns and processes in the context of state transitions (or regime shifts) and draw upon examples from semiarid ecosystems to illustrate these linkages. We suggest three spatial perspectives be used to expand conceptual state-and-transition (S\&T) models to landscape systems. First, S\&T models should represent how spatial patterns of natural and anthropogenic drivers interact to initiate transitions. This would account for often observed situations wherein contrasting states occur along gradients of disturbance intensity or in different management units. Second, spatial dependence in response to drivers and triggers should be represented. This would help account for observed differences in ecological resilience tied to inherent spatial variation in environmental variables (e.g., soil and landform attributes) that mediate driver effects and lead to variation in the likelihood of state transitions. Third, the nature of feedbacks, how they propagate over time and space, and how they are conditioned by patterns of spatial dependence and drivers should be represented. At fine scales, changes in the nature and intensity of feedbacks may be associated with predictable changes in patch structure (e.g., fragmentation or coalescence processes foreshadowing thresholds). At coarser scales, feedbacks may be associated with the spatial extent and arrangement of land cover states, broad-scale resource redistribution (e.g., wind/water erosion/deposition) or land surface/climate interactions. S\&T conceptual models with a spatial component would make use of readily-obtainable patch-scale data to predict how the likelihood of transitions might vary across landscapes and to forecast changes leading to degradation or recovery. Such predictions would be valuable in the design of monitoring schemes aimed at adjusting management to avert crossing degradation thresholds and to take advantage of environmental conditions required to restore desired states.}, keywords = {Chihuahuan Desert, contagion, Iceland, monitoring, patch dynamics, regime shift, southern Great Plains, spatial dependence, thresholds}, doi = {doi: 10.1111/j.1365-2664.2011.01982.x}, url = {/files/bibliography/11-007.pdf}, author = {Brandon T Bestelmeyer and D. Goolsby and Steven R. Archer} } @proceedings {49930, title = {State-and-transition model archetypes: A global taxonomy of rangeland change}, volume = {IX}, year = {2011}, month = {04/2011}, pages = {60}, address = {Roxario, Argentina}, abstract = {State and transition models (STMs) synthesize science-based and local knowledge to formally represent the dynamics of rangeland and other ecosystems. Mental models or concepts of ecosystem dynamics implicitly underlie all management decisions in rangelands and thus how people influence rangeland sustainability. STMs use a combination of elements, including structured inventory and mapping, historical reconstruction, process-based comparisons and experiments, and local knowledge to develop formal models of ecosystem function. The models describe the mechanisms by which transitions among states occur and thus the interventions needed to achieve or sustain desired states. STMs are very useful tools, but are often difficult to construct. We ask whether we can identify a series of basic, archetypal models globally that could be matched to local ecosystems and assist in the development of local STMs.}, keywords = {conservation practices, ecological sites, monitoring, succession, thresholds}, author = {Brandon T Bestelmeyer and H. Raul Peinetti and Jeffrey E. Herrick and Diego Steinaker and Edgardo Adema} } @article {49982, title = {Cross-system comparisons elucidate disturbance complexities and generalities}, journal = {Ecosphere}, volume = {2}, year = {2011}, month = {07/2011}, pages = {Article 81}, chapter = {1}, abstract = {Given that ecological effects of disturbance have been extensively studied in many ecosystems, it is surprising that few quantitative syntheses across diverse ecosystems have been conducted. Multi-system studies tend to be qualitative because they focus on disturbance types that are difficult to measure in an ecologically relevant way. In addition, synthesis of existing studies across systems or disturbance types is challenging because sufficient information needed for analysis is not easily available. Theoretical advances and improved predictions can be advanced by generalizations obtained from synthesis activities that include multiple sites, ecosystems, and disturbance events. Building on existing research, we present a conceptual framework and an operational analog to integrate this rich body of knowledge and to promote quantitative comparisons of disturbance effects across different types of ecosystems and disturbances. This framework recognizes individual disturbance events that consist of three quantifiable components: (1) environmental drivers, (2) initial system properties, and (3) physical and biological mechanisms of effect, such as deposition, compaction, and combustion. These components result in biotic and abiotic legacies that can interact with subsequent drivers and successional processes to influence system response. Through time, a coarse-scale quasi-equilibrial state can be reached where variation in drivers interacting with biotic processes and feedbacks internal to the system results in variability in dynamics. At any time, a driver of sufficient magnitude can push the system beyond its realm of natural variability to initiate a new kind of event. We use long-term data from diverse terrestrial ecosystems to illustrate how our approach can facilitate cross-system comparisons, and provide new insights to the role of disturbance in ecological systems. We also provide key disturbance characteristics and measurements needed to promote future quantitative comparisons across ecosystems.}, keywords = {disburbance event, disturbance type, drought, ecological theory, global change, hurricane legacies, overgrazing, thresholds, wildfire}, doi = {10.1890/es11-00115.1}, url = {/files/bibliography/11-015.pdf}, author = {Debra C. Peters and Ariel E. Lugo and F.S. Chapin III and Steward T.A. Pickett and Danielle Duni and Rocha, Adrian V. and F. J. Swanson and C. Laney and J. W. Jones (eds.)} } @article {50415, title = {Threshold Concepts and Their use in Rangeland Management and Restoration: The Good, The Bad and the Insidious}, journal = {Restoration Ecology}, volume = {14}, number = {3}, year = {2006}, month = {September 1, 200}, pages = {325-329}, chapter = {325}, abstract = {Ecological thresholds describe abrupt changes in ecological properties in time or space. In rangeland management, thresholds reflect changes in vegetation and soils that are expensive or impossible to reverse. The threshold concept has catalyzed important advances in rangeland management thinking, but it has also introduced two classes of drawbacks. First, the ambiguity of the term "threshold" and the desire for simplicity in its application has led to an over-emphasis on classification thresholds, such as vegetation cover values. Uncritical use of classification thresholds may lead to the abandonment of management efforts in land areas that would otherwise benefit from intervention. Second, it is possible that the invocation of thresholds and irreversible degradation may eventually result in the wholesale conversion of land areas that would have been recoverable or served important societal functions, such as biodiversity maintenance, that are not reflected in threshold definitions. I conclude with a recommendation to clarify the nature of thresholds by defining the relationships among pattern, process, and degradation and distinguishing preventive thresholds from restoration thresholds. We must also broaden the attributes used to define states and thresholds.}, keywords = {biodiversity, ecological thresholds, exurban development, grazing, landscape ecology, rangeland health, state-and-transition models, thresholds}, url = {/files/bibliography/06-030.pdf}, author = {Brandon T Bestelmeyer} } @conference {50589, title = {Cross Scale Interactions and Spatial Nonlinearities: An Interdisciplinary Framework}, booktitle = {Ecological Society of America 90th Annual Meeting}, year = {2005}, month = {August 7-12, 200}, pages = {504}, address = {Montreal, Quebec, CANADA}, abstract = {Thresholds caused by nonlinear interactions and feedbacks across spatial scales are common features of ecological and physical systems. Spatial nonlinearities (i.e., acceleration or deceleration in the rate of change as the spatial extent expands) challenge the ability of ecologists to understand and predict system behavior at one scale based on information obtained at finer or broader scales. Thus, cross-scale interactions often result in {\textquotedblleft}surprises{\textquotedblright} with severe consequences for the environment (e.g., wildfire, pest outbreaks, state changes) and human welfare (e.g., spread of infectious diseases). Alternatively, cross scale interactions may be beneficial, such as accelerated recovery of vegetation following fire. In both cases, fine scale processes propagate nonlinearly to have unexpected effects at broader spatial scales. In many cases, climate variability and its effects on ecosystems, is a mechanism for cross-scale synchronization of ecosystem pattern and process.Identification of the key processes generating the nonlinear behavior is often problematic. We present a conceptual framework for understanding and forecasting events that result from cross scale interactions. We provide support for our framework using both historical (the Dust Bowl) and current examples (wildfires, invasive species). This paper provides the introduction for a series of papers on the importance of cross scale interactions to the dynamics of a variety of ecological systems.}, keywords = {ecological, nonlinear, sptaial, thresholds}, author = {Debra C. Peters and Brandon T Bestelmeyer} } @article {50597, title = {Ecological and geographical scale: Parallels and potential for integration}, journal = {Progress in Human Geography}, volume = {29}, year = {2005}, month = {06/2005}, pages = {276-290}, chapter = {276}, abstract = {

Scale has emerged as a major conceptual issue in both ecology and human geography in recent decades, due principally to the appearance of new global problems and processes that challenge conventional disciplinary theories and methods. Yet, very little work has examined ecological and geographical scale side by side or attempted to bring them into constructive engagement. This is unfortunate because human geography can help address ecologists\&$\#$39; expressed need for greater attention to political and economic processes affecting ecosystems and because ecological scale can provide needed conceptual and methodological clarity to \&$\#$39;the scale question\&$\#$39; in geography. This paper reviews recent debates about scale in the two disciplines and presents the case for integration, not by reduction of geographical problems to ecological ones but on the basis of a shared interest in understanding the complex interactions of multiscaled processes. Three distinctions articulated by ecologists are missing from the debate among human geographers: between scale and level, between empirical and methodological dimensions of scale, and, within the methodological dimension, between grain and extent. I show how these distinctions help resolve recent disputes in human geography, outline a framework for research on scale, and illustrate my points with a brief case study.

}, keywords = {ecological scale, geographical scale, human geography, rabgeland ecology, scaling effects, thresholds}, doi = {10.1191/0309132505ph546oa}, url = {/files/bibliography/05-026.pdf}, author = {N. F. Sayre} } @article {50637, title = {Land management in the American Southwest: A state-and-transition approach to ecosystem complexity}, journal = {Environmental Management}, volume = {34}, number = {1}, year = {2004}, month = {July 1, 2004}, pages = {38-51}, abstract = {

State-and-transition models are increasingly being used to guide rangeland management. These models provide a relatively simple, management-oriented way to classify land condition (state) and to describe the factors that might cause a shift to another state (a transition). There are many formulations of state-and-transition models in the literature. The version we endorse does not adhere to any particular generalities about ecosystem dynamics, but it includes consideration of several kinds of dynamics and management response to them. In contrast to previous uses of state-and-transition models, we propose that models can, at present, be most effectively used to specify and qualitatively compare the relative benefits and potential risks of different management actions (e.g., fire and grazing) and other factors (e.g., invasive species and climate change) on specified areas of land. High spatial and temporal variability and complex interactions preclude the meaningful use of general quantitative models. Forecasts can be made on a case-by-case basis by interpreting qualitative and quantitative indicators, historical data, and spatially structured monitoring data based on conceptual models. We illustrate how science- based conceptual models are created using several rangeland examples that vary in complexity. In doing so, we illustrate the implications of designating plant communities and states in models, accounting for varying scales of pattern in vegetation and soils, interpreting the presence of plant communities on different soils and dealing with our uncertainty about how those communities were assembled and how they will change in the future. We conclude with observations about how models have helped to improve management decision-making.

}, keywords = {Chihuahuan Desert, community dynamics, desert grassland, grazing management, rangeland, resilience, simulation models, soil maps, thresholds}, doi = {10.1007/s00267-004-0047-4 }, url = {/files/bibliography/04-015.pdf}, author = {Brandon T Bestelmeyer and Joel R. Brown and Jeffrey E. Herrick and D. Trujillo and Kris Havstad} } @proceedings {50887, title = {Integration of soil indicators into multi-attribute rangeland monitoring and assessment systems}, volume = {Report QNRM02143}, year = {2002}, month = {August 1-6, 1999}, publisher = {Queensland Department of Natural Resources and Mines, Australia 2002}, address = {Brisbane, Australia}, abstract = {Rangeland health and soil quality are frequently defined in terms of the capacity of the land to conserve soil and water resources, cycle nutrients and support productive plant communities. Rangeland monitoring programs in most countries have traditionally focused, almost exclusively, on plant community composition. An implicit assumption is that other properties and processes are correlated with vegetation, so measurements are unnecessary. In many cases, however, soil degradation or improvement can occur in the absence of easily detectable vegetation changes until a threshold is crossed resulting in dramatic and frequently irreversible changes in plant community composition. We suggest that easily-measured soil properties can serve as early-warning indicators of potential transitions between vegetation states in rangeland ecosystems. These indicators and associated vegetation measurements are by no means universal. Both the selections of quantitative indicators and the identification of appropriate monitoring points depend on monitoring objectives and resource availability. Rapid, qualitative indicators can aid in the design of a quantitative monitoring program. They can also be applied together with quantitative indicators to aid interpretation. We describe how quantitative and qualitative soil and vegetation indicators can be used together to monitor rangeland health.}, keywords = {assessment, monitoring, rangeland health, soil and water conservation, soil quality, thresholds}, isbn = {0 7345 2668 7}, url = {/files/bibliography/02-097.pdf}, author = {Jeffrey E. Herrick and Kris Havstad}, editor = {Lawrence, P.A. and Robinson, J.} }