MANAGEMENT TECHNOLOGIES FOR ARID RANGELANDS
Location: Range Management Research
Title: Spatially-explicit representation of state-and-transition models
Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 28, 2012
Publication Date: May 15, 2012
Citation: Steele, C.M., Bestelmeyer, B.T., Burkett, L.M., Smith, P., Yanoff, S. 2012. Spatially-explicit representation of state-and-transition models. Rangeland Ecology and Management. 65:213-222.
Interpretive Summary: If we want to monitor natural resources over large areas, we need to know something about how these resources are distributed. The most useful tool for this is a map that can link what we see at a point on the ground to a broader area. We have used the existing ecological site concepts developed by the Natural Resources Conservation Service (NRCS) to develop such a map and database. Ecological sites are a way to categorize areas of land according to its potential to produce a certain type of characteristic vegetation. Ecological sites themselves are determined by their soils and the position in the landscape. The NRCS have developed block and arrow diagrams (state-and-transition models) to describe how vegetation might change at different ecological sites under diffferent environmental conditions (e.g., drought, grazing. We have created a simple method whereby each possible vegetation state can be mapped to its ecological site. We applied this method using aerial photography of public lands in Southern New Mexico. This paper describes the rationale for mapping vegetation states and covers the steps we took to produce the map and database.
The broad-scale assessment of natural resource conditions (e.g., rangeland health, restoration needs) requires knowledge of their spatial distribution. We argue that creating a database that links state-and-transition models (STMs) to spatial units is a valuable management tool for structuring ground-based observations, management planning for landscapes, and for housing information on the responses of land areas to management actions. To address this need, we introduce a multi-factor classification system based on ecological sites and STMs that is directly linked to recent concepts of vegetation dynamics in rangelands. We describe how this classification was used as a basis for creating a spatial database and maps of ecological states. We provide an example of how the classification and mapping has been applied in over 1.2 million ha of public rangelands in southern New Mexico using aerial photo interpretation supplemented with existing inventory data and rapid field assessments. The resulting state map has been used by the Bureau of Land Management (BLM) to design landscape-level shrub control efforts, structure and report district-wide rangeland health assessments, and to evaluate locations for energy development. We conclude by discussing options for the development of state maps and their current limitations, including the use of satellite imagery and concepts for defining states. We argue that cataloging ecological states in a spatial context has clear benefits for rangeland managers because it connects STM concepts to specific land areas. State mapping also provides a means to generate and store spatially-explicit data resulting from tests of the propositions in STMs and conservation practices.