Water chemistry of throughfall, stemflow, and soil solutions in Guandaushi forest watershed

Bor-Hung Sheu

Department of Forestry, National Chung-Hsing University, Taichung, Taiwan

The objectives of this study were to examine the water chemistry of precipitation, throughfall, stemflow and soil solutions under three stands, China-fir (Cunninghamia lanceolata) plantation, secondary hardwood stand, and natural hardwood stand in Guandaushi Forest, in central Taiwan during July 1995 to June 1997. The dominant cation and anion in bulk precipitation were hydrogen ion and sulfate, respectively. Whereas hydrogen was attenuated by the canopies of two hardwood stands, sodium, calcium, magnesium, potassium, sulfate, nitrate, and bicarbonate were released by the canopies. The canopy modification of the hydrogen flux was more remarkable under the two hardwood stands than under the China-fir stand, suggesting that the efficiency of broadleaves as the collectors of dry deposition is greater than that of conifers. On the other hand, great amounts of sulfate and few ammonia were retained by the China-fir canopy. Though the pH of throughfall was greater than that of bulk precipitation in all stands, that of stemflow was only greater in the two hardwood stands. Soil moisture and soil water concentrations also varied among three stands. Results indicated that ion concentrations of bulk precipitation changes considerably as it passes through the canopy, litter and soil. The buffering capacity of the system eliminates adverse inputs.