Integrating Dynamic Soil and Vegetation Properties Into Ecosystem Service-Based State and Transition Models to Guide Rangeland Management.

California's annual rangelands cover approximately 6.4 million hectares, and produce 70% of the state's forage base. This ecosystem supports more than 300 vertebrate, 5000 invertebrate, and 2000 plant species. Annual rangeland soils have the capacity to support high primary productivity and accumulate significant belowground organic matter. Additionally, over 85% of California's drinking water supply is generated and stored annually within rangeland watersheds. Widespread degradation of annual rangelands is driven by: 1) Blue oak (Quercus douglasii) tree removal for fuel wood and increased livestock carrying capacity; 2) Persistent weed invasion; and 3) Improper grazing management (e.g., continuous, heavy wet season grazing). These drivers create conditions that may deliver different levels of ecological services.

State and transition models have been utilized to catalog ecological information and assess management risks and benefits on rangeland sites. These models are one approach to describing the various states a particular site can achieve, the forces that transition sites between states, and the role range management plays in the process. In the oak rangeland ecological sites of the Sierra Nevada Foothills, development of state and transition models has been based upon vegetation properties, with little integration of soil change and ecosystem services derived from plant-soil interactions (e.g., carbon sequestration, soil water storage, biodiversity).

We will discuss the integration of dynamic soil and vegetation properties into ecosystem service-based state and transition models for oak rangeland ecological sites. We will present data supporting the: 1) Identification  of cost-effective and easily measurable proxies for dynamic soil and vegetation properties supporting key ecosystem services; 2) Identification of ecologically unique sites and states based upon plant-soil dependent ecosystem services; 3) Quantification of associations between dynamic properties, ecosystem services, and oak and grazing regimes to assess potential for management; and 4) Determination of  ecological resilience of sites and states to grazing management.