Post-fire influences of snag attrition on albedo and radiative forcing

Tuesday, 16 December 2014
Thomas L O'Halloran1, Steven A Acker2, Verena Joerger1, Jane Kertis3 and Beverly Elizabeth Law4, (1)Sweet Briar College, Sweet Briar, VA, United States, (2)Willamette National Forest, Springfield, OR, United States, (3)Siuslaw National Forest, Corvallis, OR, United States, (4)Oregon State University, Corvallis, OR, United States
We examine albedo perturbation and associated radiative forcing after a high-severity fire in a mature forest in the Oregon Cascade Range. Correlations between post-fire albedo and seedling, sapling, and standing dead tree (snag) density were investigated across fire severity classes and seasons for years 4-15 after fire. Albedo perturbation was 14 times larger in winter compared to summer and increased with fire severity class for the first several years after fire. Summer and winter albedo perturbation increased approximately linearly over the study period. Albedo correlations were strongest with snags, and significant in all fire classes in both summer and winter. The resulting annual radiative forcing at the top of the atmosphere decreased (became more negative) linearly for the first 15 years after fire. These results suggest that snags, more than recovering vegetation, can control the shortwave energy balance of the burned land surface. As such, the dynamics of snag attrition may need to be included in coupled land-atmosphere models to properly represent the climate impacts of wildfire.