Tracking Post-Wildfire States and Transitions in the Sagebrush-Steppe
The Arid Lands Ecology Reserve of the Hanford Reach National Monument formerly contained one of the last major expanses of Wyoming big sagebrush-dominated habitat in the mid-Columbia Basin. However, increasing wildfire frequency and extent, in response to growing numbers of anthropogenic ignitions and changes in fuel structure caused by cheatgrass invasion have caused successive and noticeable reductions in sagebrush cover. To fully evaluate the effects of repeated disturbances and to prioritize and evaluate restoration activities, managers need to understand how entire vegetation communities change over time. Despite this, changes to the structure of vegetation communities as a whole are difficult to visualize and often rely on analytically-intensive multivariate statistical methods. In contrast state and transition models are easy to use but may lack generally applicability and only describe qualitative changes in plant communities. We are developing a simple quantitative method to track changes in sagebrush--steppe vegetation community structure. The model has two axes, one relating to shrub dominance and the other to dominance by native species. This model can be used to track transitions following wildfires and restoration treatments and can also be used to assess the resistance and resilience of communities in relation to disturbance and dominant plant traits. We hope the method will be useful for managers wanting a cost-effective methods to evaluate the effects of their management actions in shrub-steppe ecosystems.