Summertime Radiation Balances of Clearcut and Shelterwood Slopes in Southwest Oregon
Authors: Holbo, H. R.; Childs, S. W.
Source: Forest Science, Volume 33, Number 2, 1 June 1987 , pp. 504-516(13)
Publisher: Society of American Foresters
Abstract:Measurements of incoming solar radiation, reflected solar radiation, net radiation, and outgoing longwave radiation were made on three clearcuts and below three shelterwood canopies in southwest Oregon. This dataset was used to characterize the radiation balance of reforestation sites. The fraction of incoming solar energy (K ↓) producing the near surface microclimate (i.e., the net radiation, Q*) was 0.5 ± 0.06 for all sites studied. This value is appreciably lower than commonly measured values of uncut forest (Q*/K ↓ = 0.7 to 0.9). Although Q*/K ↓ is the same for clearcuts and shelterwoods, shelterwood understories have smaller net radiation because the overstory partially intercepts incoming solar radiation. Shelterwood data also exhibit the expected decrease in longwave radiation loss at night. The major factor affecting site albedo in both shelterwoods and clearcuts was slashburning, which decreased albedo to 0.13 as compared to 0.21 for unburned sites. Net radiation for entire sites was estimated with a simple model to sum ground surface net radiation and shelterwood canopy net radiation. Model calculations suggest that harvested sites average a 36% reduction in total net radiation when compared to unharvested stands. Shelterwood understory environments are less harsh than clearcut environments because much of the total site net radiation is dissipated in the overstory canopy. The model is also used to estimate the effect of canopy density on net radiation below the canopy. For. Sci. 32(2):504-516.
Document Type: Journal Article
Affiliations: Assistant Professor, Department of Soil Science, Oregon State University, Corvallis, Oregon 97331
Publication date: 1 June 1987
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