@article {JRN54653, title = {Application of ecological site information to transformative changes on Great Basin sagebrush rangelands}, journal = {Rangelands}, volume = {38(6):379-388}, year = {2016}, abstract = {

Ecological Site Description (ESD) concepts are broadly applicable and provide a necessary framework to inform and guide rangeland management decisions. \ In this paper, we demonstrate how understanding and quantification of key vegetation, hydrology, and soil relationships in the ESD context can inform rangeland assessments and targeting of management practices in Great Basin sagebrush steppe. \ For the example presented here, integration of vegetation and relative estimates of runoff and erosion into the STM or ESD context identifies the ecohydrologic ramifications of each state transition and allows for more informed understanding of short- and long-term site responses to various management alternatives. \ We did not consider other factors important to a land management decision process, such as land use designations or goals, cost and practicality of treatment alternatives, resource availability, and broader area management objectives, however, such information is easily accommodated into an ESD-based decision-making strategy/framework. \ Although we present a single site-specific application, the same approach can be applied at the landscape scale. \ RHEM model scenarios and ecohydrologic interpretations could be developed for selected states across multiple ecological sites at the landscape-scale. \ RHEM is also the hillslope hydrology and erosion engine for the KINEROS2/AGWA model which enables simultaneous RHEM simulations across all hillslopes in one or more watersheds. \ Model results supplementing current ESD information could be used to target and optimize conservation efforts across multiple sites for maximum ecological and economic benefit. \ For example, tree removal may be more effective at locations with vegetation early in the juniper encroachment gradient and that have highly erodible soils. \ An integrated ESD-RHEM approach across multiple sites would equip a decision maker to predict potential site responses and most effectively implement resources across a landscape. \ The general approach presented here is not limited to sagebrush rangelands or to hydrologic and erosion processes. \ We demonstrate how enhancement of ESDs with key ecohydrologic information can aid predictions of ecosystem response and targeting of conservation practices for sloping sagebrush rangelands that are strongly regulated by ecohydrologic or ecogeomorphic feedbacks. \ Similar approaches could be applied to other rangeland ecosystems with other self-regulating processes, disturbances, and factors (e.g., wind erosion and evaporation on bare soils in flat terrain). We acknowledge that application of our approach may be difficult for sites with limited local knowledge and available data. \ Building and assessing ecological models and predicting plant community and ecohydrologic responses to disturbances and management are inherently more difficult in cases with limited information. \ A primary point of this work is that ESD concepts are flexible and can be creatively augmented for improved assessment and management of rangelands.

}, doi = {10.1016/j.rala.2016.10.004}, url = {files/bibliography/16-032.pdf}, author = {Jebediah C. Williamson and Frederick B. Pierson and K. Spaeth and Joel R. Brown and Al-Hamdan, Osama Z. and M.A. Weltz and Mark A. Nearing and Jeffrey E. Herrick and Boll, Jan and Robichaud, Peter R. and David C. Goodrich and Phil Heilman and Guertin, D. Phillip and Hernandez Narvaez, Mariano and Wei, Haiyan and Polyakov, Viktor and G. Armendariz and Nouwakpo, S and Stuart P. Hardegree and Patrick E. Clark and Strand, Eva K. and Bates, Jonathan D. and Loretta Metz and M. H. Nichols} } @article {JRN54577, title = {Can ecological land classification increase the utility of vegetation monitoring data?}, journal = {Ecological Indicators}, volume = {69}, year = {2016}, month = {10/2016}, pages = {657-666}, chapter = {657}, abstract = {

Vegetation dynamics in rangelands and other ecosystems are known to be mediated by topoedaphic properties. Vegetation monitoring programs, however, often do not consider the impact of soils and other sources of landscape heterogeneity on the temporal patterns observed. Ecological sites (ES) comprise a land classification system based on soil, topographic, and climate variations that can be readily applied by land managers to classify topoedaphic properties at monitoring locations. We used a long-term (\>40 y) vegetation record from southeastern Arizona, USA to test the utility of an ES classification for refining interpretations of monitoring data in an area of relatively subtle soil differences. We focused on two phenomena important to rangeland management in the southeastern Arizona region: expansion of the native tree velvet mesquite (Prosopis velutina Woot.) and spread of the introduced perennial grassLehmann lovegrass (Eragrostis lehmanniana Nees). Specifically, we sought to determine if a quantitative, ES-specific analysis of the long-term record would (1) improve detection of changes in plant species having heightened ecological or management importance and (2) further clarify topoedaphic effects on vegetation trajectories. We found that ES class membership was a significant factor explaining spatiotem-poral variation in velvet mesquite canopy cover, Lehmann lovegrass basal cover, and Lehmann lovegrass density measurements. In addition, we observed that the potential magnitude of velvet mesquite and Lehmann lovegrass increases varied substantially among ES classes. Our study brings attention to a practical land management tool that might be called upon to increase the effectiveness of vegetation-based indicators of ecosystem change.

}, keywords = {Biological invasion, land classification, monitoring, soil texture, Time series, Vegetation indicator}, doi = {10.1016/j.ecolind.2016.05.030}, url = {/files/bibliography/16-011.pdf}, author = {Jebediah C. Williamson and Brandon T Bestelmeyer and M.P. McClaran and D. Robinett and D.D. Briske and X. Ben Wu and Maria Fern{\'a}ndez-Gim{\'e}nez} } @article {49915, title = {Spatiotemporal patterns of production can be used to detect state change across an arid landscape}, journal = {Ecosystems}, volume = {15}, year = {2012}, month = {01/2012}, pages = {34-47}, chapter = {34}, abstract = {Methods to detect and quantify shifts in the state of ecosystems are increasingly important as global change drivers push more systems towards thresholds of change. Temporal relationships between precipitation and aboveground net primary production (ANPP) have been studied extensively in arid and semiarid ecosystems, but rarely has spatial variation in these relationships been investigated at a landscape scale, and rarely has such information been viewed as a resource for mapping the distribution of different ecological states. We examined the broad-scale effects of a shift from grassland to shrubland states on spatiotemporal patterns of remotely sensed ANPP proxies in the northern Chihuahuan Desert. We found that the Normalized Difference Vegetation Index (NDVI), when averaged across an eight-year period, did not vary significantly between these states, despite changes in ecosystem attributes likely to influence water availability to plants. In contrast, temporal relationships between precipitation and time-integrated NDVI (NDVI-I) modeled on a per-pixel basis were sensitive to spatial variation in shrub canopy cover, a key attribute differentiating ecological states in the region. The slope of the relationship between annual NDVI-I and two year cumulative precipitation was negatively related to, and accounted for 71\% of variation in, shrub canopy cover estimated at validation sites using high spatial resolution satellite imagery. These results suggest that remote sensing studies of temporal precipitation-NDVI relationships may be useful for deriving shrub canopy cover estimates in the region, as well as for mapping other ecological state changes characterized by shifts in long-term ANPP, plant functional type dominance, or both.}, keywords = {aboveground net primary production, Chihuahuan Desert state change, grassland, normalized difference vegetation index, precipitation, remote sensing, shrub encroachment, shrubland}, doi = {10.1007/s10021-011-9490-2}, url = {/files/bibliography/12-003.pdf}, author = {Jebediah C. Williamson and Brandon T Bestelmeyer and Debra C. Peters} } @conference {JRN54587, title = {Towards broad-scale perspectives on landscape dynamics: The National Ecological Dynamics Database}, booktitle = {Society for Range Management, 65th Annual Meeting}, year = {2012}, month = {10/2011}, publisher = {Society for Range Management}, organization = {Society for Range Management}, address = {Spokane, WA}, abstract = {Ecological site descriptions (ESDs) are a useful technology for conveying the ecological potential of specific land types and the possible responses of vegetation and soils on them to management. Yet some of the same traits that lend ESDs their management utility (e.g., narrative format and site-specific focus) also make them an inefficient resource for broader-scaled analyses, such as comparing ecological processes among regions or producing national maps of conservation needs. Such objectives would be better served by a database in which ecological information for a region can be (1) readily queried and (2) easily analyzed in a geographic information system. To help address this need, we have initiated development of a National Ecological Dynamics Database (NEDD), which aims to identify and describe ecological dynamics of primary management concern at the level of Major Land Resource Areas. This database will catalog information pertinent to such dynamics in a relational geodatabase format. The core objectives of the NEDD are to (1) promote nationwide consistency in ESD development and (2) provide a national view of potential ecological states (in the sense applied to state-and-transition models), their dynamics, restoration successes and failures, and the factors determining the patterns and types of ecological change observed at landscape to continental scales. As a first step in designing and populating the NEDD, data are being harvested from ESDs currently available. Here, we present insights from this initial exercise and describe in more detail the background, goals, design, and expected utility of this new database.}, author = {Jebediah C. Williamson and Brandon T Bestelmeyer} } @article {50003, title = {Reinterpreting historical data for evidence-based shrubland management}, journal = {Natural Resources and Environmental Issues}, volume = {17}, year = {2011}, month = {01/15/2011}, pages = {1-10}, chapter = {Article 18}, abstract = {

Long-term vegetation dynamics in the Chihuahuan Desert of southern New Mexico have been intensively studied for over a century, and interpretations of the broad scale drivers of these dynamics are numerous. We now understand that interpretation of spatially heterogeneous change requires a more nuanced, contextualized, and detailed understanding of edaphic features and landscape characteristics. Recently, state and transition models (STMs) have been employed to represent landscape-specific dynamics for each ecological site within a Major Land Resource Area (MLRA). We re-examined data characterizing vegetation across the public lands of the northern Chihuahuan Desert at two points in time, the 1930s and 2005. In this study, our objectives were to (1) develop geospatial data layers of historical and current vegetation states, (2) compare vegetation states between the 1930s and 2005 where the two data layers overlap, and (3) interpret any major vegetation state changes over this ~70 year period within the context of specific ecological sites. It was our hypothesis that ecological dynamics would vary in interpretable ways among ecological sites. Three primary observations are drawn from our results: (1) the bulk of the region was relatively stable during this period, (2) approximately the same amount of area experienced increased grass dominance as experienced increased shrub dominance, and (3) dynamics are strongly influenced by the properties of specific ecological sites. Major vegetation state changes, involving either increased grass dominance or increased shrub dominance, only occurred to any extent in 11 of 18 ecological sites within this study area. More important to management, significant increases in shrubs occurred within only four ecological sites. These sites were sandy, deep sand, shallow sandy, and gravelly sand. All other ecological sites within this region were relatively stable over the ~70 year period between observations. The obvious management implication is the importance of stratifying by ecological site prior to application of shrub control treatments.

}, url = {/files/bibliography/11-040.pdf}, author = {Jebediah C. Williamson and Laura M. Burkett and Brandon T Bestelmeyer and R. K. Skaggs and Kris Havstad} } @conference {JRN54455, title = {Differences in MODIS EVI-based rainfall use efficiency among ecological states of the northern Chihuahuan Desert}, booktitle = {63rd Society for Range Management Annual Meetings}, year = {2010}, month = {02/2010}, publisher = {Sociiety for Range Management}, organization = {Sociiety for Range Management}, address = {Denver, CO}, abstract = {

Shrub encroachment into grasslands of the northern Chihuahuan Desert has resulted in often dramatic and geographically extensive changes in vegetation composition and soil structure. The nature of these transformations and their dependencies on soil characteristics have been largely conceptualized in state and transition models. Reduced perennial plant cover and heightened erosion in shrub interspaces suggests a reduced capacity for shrub-dominated sites to convert rainfall, typically the limiting resource in arid ecosystems, into plant biomass. We examined this hypothesis in the Jornada Basin, New Mexico using the MODIS Enhanced Vegetation Index (EVI) as a surrogate for primary productivity. The time frame of the study (2002-2008) coincided with a regional transition from below to above normal rainfall, providing an opportunity to assess vegetation response to increased moisture availability. A relatively dense network of rain gauges on the Jornada Experimental Range and Chihuahuan Desert Rangeland Research Center allowed for satisfactory rainfall interpolation at the scale of MODIS 250 meter imagery. Problems arising from spatial heterogeneity in soil brightness and vegetation structure were reduced by computing linear relationships between annual integrated EVI (I-EVI) and rainfall on a per-pixel basis across the study area. The coefficient of determination (r2), slope and intercept of these regressions were then mapped as a means of assessing spatial patterns in rainfall use efficiency (RUE). Here, we illustrate the results of this approach. We evaluate RUE metrics against ground-based ecological state classifications and satellite-derived shrub cover estimates, and we show that temporal, pixel-based assessments of RUE offer valuable insight into the functioning of Chihuahuan Desert vegetation states, despite some common problems associated with interpreting vegetation indices in ecosystems with low and diverse plant cover.

}, author = {Jebediah C. Williamson and Brandon T Bestelmeyer} }