Soil Response to Recurring Fire in the Sagebrush Steppe of the Northern Columbia Basin

Sagebrush steppe is one of the largest ecosystems in North America. Fire frequency has increased significantly in these ecosystems, and this alters soil structure and function. Changes in soil can feedback to alter plant communities, leaving the system comprised of a plant community that differs considerably from its original state. However, the impact of fire frequency on the rate of ecosystem change is uncertain. This research aims to understand how fire frequency in sagebrush ecosystems affects soil structural and functional properties that are critical for the plant community. Our study area includes approximately 50,000 acres of sagebrush steppe in the northern Columbia Basin of Washington state. The study area has experienced repeated, overlapping natural fires in recent years (2003, 2007, and 2012). Soil samples were collected in August of 2016 from sites that were exposed to one, two, or all three of these fires. To assess fire impacts on soil structure we quantify changes in aggregate assembly and soil C contents. To assess impact on soil function, we evaluate soil enzyme activity, and soil microbial activity. This research will provide data that help land managers to make informed decisions on land management strategies to conserve these ecosystems