Albedo Following Fire in a Northern Hardwood Forest

Abstract

Changes in albedo were tracked following fire on 18 August 1980 in a successional hardwood forest in northern lower Michigan (43°33?N, 84°42?W). Shortwave albedo (300?3000 nm) changed little with zenith angle up to 55°, but then increased rapidly. The rate of change in albedo with zenith angle was highest in July and lowest in early spring and late autumn. Midday albedo increased from 7.7% five days after the fire to 10.8% after six weeks. During the 1981 and 1982 growing seasons, albedo increased from 10.4 and 13.6% in mid-May to peaks of 17.8 and 18.1% in early July, respectively, with values then declining through autumn. Albedo increased with percent coverage of ground surface with live vegetation up to 35% cover, with little further change in albedo with cover, up to the maximum oberved value of 70%. The ratio at midday of albedo in visible wavelengths (400?700 nm) to total shortwave albedo decreased from 0.49 in mid-May 1982 to a minimum of 0.22 in mid-July and then increased to 0.45 in mid-October, after leaf-fall. Midday shortwave albedo during winter varied from 91% over fresh snow to 76% over old, compacted snow.