Estimation of net radiation for a coniferous forest, and the effects of logging on net radiation and the reflection coefficient

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Abstract
The results of field studies on the radiation climate at Montmorency, Quebec, are presented. These studies were conducted in the summers of 1975 and 1976, and two sites were used. The first site, used in both years, was forested with 50- to 60-year-old balsam fir (Abiesbalsamea L. Mill.). The second site, originally forested with balsam fir, was clear-cut in the fall of 1975. The daily mean reflection coefficient for solar radiation of the forest is 7% (sample of 264 hourly values). In contrast, the clear-cut site has a daily mean reflection coefficient of 18% (sample of 171 hourly values). There is no evidence of a systematic variation of hourly reflection coefficients with solar zenith angle for either site. The effect of logging on net radiation is characterized by a sample of 21 days in 1976 when hourly values of net radiation were available for both sites. Typically, during the night, the magnitude of net radiation on the forested site is less than that on the clear-cut site, and during the day, the net radiation on the clear-cut site is less than that on the forested site. In terms of daily totals, the effect of logging is to reduce net radiation by 10%.A simple linear regression equation for the calculation of net radiation for the forested site is presented. Global solar radiation (hourly values) is used as the predictor. The parameters of the model are similar to other equations for similar surfaces.

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