Seasonal and spatial variations and the effects of clear-cutting in the methane absorption rates of a temperate forest soil

Methane absorption rates of soils in a deciduous broad-leaf secondary fores t dominated by Quercus serrata in central Japan were measured by closed cha mber technique from July 1995 to March 1999, focusing on its seasonal and s patial variations and the effects of clear-cutting. The measurement indicat ed that the methane absorption rate was the highest from late summer to beg inning of autumn. The maximum value of the mean absorption rate was about 0 .1 CH4 m(-2) hr(-1). Regarding the spatial variation of the absorption rate , it varied along the position in a slope: the rate was higher at the lower position in a slope and lower at the upper position. After clear-cutting i n the one of two adjacent watersheds constituting the study site, the highe st mean absorption rate decreased to about 60-70 % of the last year's rate; our observations suggest that partial disturbance and erosion of the surfa ce soil was the main reasons for the decrease.