Postfire influences of snag attrition on albedo and radiative forcing

Abstract

This paper examines albedo perturbation and radiative forcing after a high-severity fire in a mature forest in the Oregon Cascade Range. Correlations between postfire albedo and seedling, sapling, and snag (standing dead tree) 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. Albedo perturbation increased linearly with time over the study period. Correlations between albedo perturbations and the vegetation densities were strongest with snags, and significant in all fire classes in both summer and winter (R < -0.92, p < 0.01). The resulting annual radiative forcing at the top of the atmosphere became more negative linearly at a rate of -0.86 W m -2 yr -1, reaching -15 W m -2 in year 15 after fire. This suggests that snags can be the dominant controller of postfire albedo on decadal time scales. Key Points Snag attrition controls postfire albedo more than vegetation recoveryAlbedo perturbation was 14 times larger in winter compared to summerNegative radiative forcing increases linearly for at least 15 years postfire