台灣杉造林地溪流水化學之研究

Biogeochemistry cycling is widely employed in hydrological studies to investigate nutrition cycling, water chemistry, and streamflow generation mechanisms in a watershed. Many such researches have been conducted on natural broadleaf forests in Taiwan, but few studies were implemented in conifer forests, especially in conifer plantation. Therefore, this paper aimed to investigate streamwater chemistry in a Taiwania-fir plantation in the Liukuei Experimental Forest, southern Taiwan. Monthly variation of streamwater chemistry was also analyzed. The study area is 17.8 ha in size with an average slope of 60%. Main vegetation cover is Taiwania-fir (Taiwania cryptomerioides) plantation, 28 years old in age. From 1999 January to 2000 December, monthly discharges were recorded. Water samples were collected monthly and analyzed for their chemical constituents. Results showed that streamwater had weakened alkalinity with an average pH of 7.62. Dominant cation was Ca^(2+) (430 μeq L^(-1)), followed by Mg^(2+) (228 μeq L^(-1)). Dominant anion was HCO_(3^-) (534 μeq L^(-1)), followed by SO_(4^(2-)) (227 μeq L^(-1)). The total concentration of cations was 834 μeq L^(-1), while the total concentration of anions was 792 μeq L^(-1). The ratio of cations/anions was 1.05. According to Pearson correlation analysis, conductivity, concentrations of Na^+, Ca^(2+), Mg^(2+), SO_(4^(2-)), and HCO_(3^-) in streamwater decreased with increasing discharge. While, concentration of H^+ and NO_(3^-) increased with increase in discharge.