The budgets of nutrients and major ions between the input flux from atmospheric deposition and the output flux to streams were measured on three forested small mountain watersheds, Aburahi-N (23.8 ha), Aburahi-S (3.8 ha, 2 km south from Aburahi-N) and Myokoji (1.77 ha, 28 km northwest from Aburahi-N), located at 34-35 N and 136 E around the central part of Japan. The bedrock of the watersheds is granite. The main vegetation of Aburahi-N and Aburahi-S was planted with Japanese cypress (Chamaecyparis obtusa Sieb. et Zucc), and Myokoji was a secondary forest growing deciduous broadleaf trees and Japanese red pine. The chemical analysis of the stream waters was carried out once a week at Aburahi-N from 1987 to 1991, at Aburahi-S from 1995 to 1998, and at Myokoji from 1991 to 1993. Wet and dry depositions were collected every month at Aburahi-N. The annual mean concentrations of total nitrogen (TN) of the stream water of Aburahi-N, Aburahi-S and Myokoji were 0.408, 0.614 and 0.349 mg/l, respectively, total phosphorus (TP) contents were 0.0074, 0.0046 and 0.0096 mg/l, and the potassium ion (K+) contents were 0.83, 0.49 and 0.77 mg/l. The average annual output fluxes of TN from the watersheds of Aburahi-N, Aburahi-S and Myokoji were calculated to be 5.85, 4.10 and 12.7 kg/ha/y, TP 0.131, 0.045 and 0.280 kg/ha/y, K+ 9.63, 3.23 and 9.70 kg/ha/y, and discharge 1062, 508 and 1265 mm/y, respectively. The annual outputs tended to increase as the annual precipitation increased. The average annual input fluxes of TN, TP and K+ for six years from 1990-1998 were 12.5, 1.31 and 7.64 kg/ha/y, respectively, and the precipitation averaged 1449 (1019-1947) mm/y.

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