Ecological Sites & State-and-Transition Models

Main Points

• "An ecological site is defined as a distinctive kind of land with specific soil and physical characteristics that differ from other kinds of land in its ability to produce a distinctive kind and amount of vegetation and its ability to respond similarly to management actions and natural disturbances." - NRCS
    
• State and transition models (STMs) are key components of ecological site descriptions. STMs are one way of describing the multiple states and associated ecosystem services that a particular site can achieve; thresholds and ecological resilience of individual states to stressors; and underlying roles of management practices and natural processes in pushing a site between states.
         

Information Sources

• NRCS (Natural Resources Conservation Service). 2003. National Pasture and Range Handbook, Rev. 1. Grazinglands Technical Institute, USDA Natural Resources Conservation Service.
     
• Soils Ecological Site Inventory (SoilsESI) - Rangeland
     
• Map of Major Land Resource Areas (MLRA) in California
    

State and Transition Models - General Concepts and Methods

• Bestelmeyer et al. 2003. Development and use of state-and-transition models for rangelands.
      
• Briske et al. 2005. State-and-transition models, thresholds, and rangeland health: A synthesis of ecological concepts and perspectives.
      
• Stringham et al. 2003. State and transition modeling: An ecological process approach.
      
• Stringham et al. 2001. State, transitions, and thresholds: Further refinement for rangeland application.
      
• Westoby et al. 1989. Opportunistic management for rangelands at equilibrium.
    

State and Transition Models - Oak Woodlands

• George et al. 1992. Application of nonequilibrium ecology to management of Mediterranean grasslands.

• Huntsinger and Bartolome. 1992. A state transition model of the ecological dynamics of Quercus dominated woodlands in California and southern Spain.

• Jackson and Bartolome. 2002. A state-transition approach to understanding nonequibibrium plant community dynamics in Californian grasslands.

• Oak woodland & annual grassland ecological site descriptions