Abstract

In a red pine (Pinus densiflora) forest, changes of pH, electric conductivity, total carbon, total nitrogen, available phosphate and available potassium in soil and runoff have been studied at intervals for 1 year after early spring fire. Phytimasses of herb and shrub were measured following the current and the subsequent year. The pH, E.C., total nitrogen and phosphate of soil in burned site wee 1.1, 1.5, 1.6 and 2.0 times higher than in unburned site, respectively. But potassium showed no significant difference. A rise in pH, E.C., and total nitrogen in burned site were maintained throught the study period while phosphate maintained 4 months after the fire. The E.C., total carbon, $NO_2-N$ and $NH_4-N$ of runoff in burned site were 1.3, 1.3, 1.3 and 29.0 times higher than in unburned site, respectively, while $NO_3-N$ in unburned site was 4 times higher than in burned site. In burned site, phytomasses of herb and shrub were 148 and 33% of unburned site in a current year and 107 and 51% in a subsequent year, respectively. The considerable amount of increase in soil nutrient after the fire was conserved by the uptake of the fast regrowing plants and by the immobilization of $NH_4=N$.

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