Session: Forest disturbances and management

Title: Effects of thinning and prescribed burning on future forest productivity and composition in southwest US

Cécile C. Remy, Dan J. Krofcheck, Alisa Keyser, Marcy E. Litvak & Matthew D. Hurteau

In the southwestern US, ongoing climate change is exacerbating a legacy of fire‐exclusion that has altered forest structure and increased high‐severity wildfire risk. It is expected that the mixed-conifer forests at high elevation will be the most impacted by the increase in high severity fires, threatening the dominant species Picea engelmannii and Abies lasiocarpa, which are not adapted to fire. Management can mitigate this risk by reducing forest density and restoring frequent surface fires in lower elevation forests, but management carries carbon costs. We sought to quantify the impact of management on the carbon storage capacity and potential tree composition changes along an elevation gradient comprising pinyon-juniper woodlands, ponderosa pine forests, and mixed-conifer forests. We simulated carbon and vegetation dynamics under projected climate and wildfires with and without thinning and prescribed burning in areas with high probability of high-severity wildfires. At a multidecadal scale, management significantly increased net photosynthesis relative to no-management, especially in ponderosa pine and mixed-conifer forests. The management scenario also resulted in more Picea engelmannii and Abies lasiocarpa at high elevations. Given the increasing climatic and disturbance pressures impacting southwestern forests, management will play a critical ensuring the continued provision of ecosystem services.