『Abstract
　For this study, characteristics and trends of the chemical constituents in bulk precipitation and streamwater were observed in a small mountainous watershed on the Shikoku Island of Japan, which covered an area of 27.4 hectares. Bulk precipitation and streamwater chemistry data spans from May 1997 to October 2004, and January 1996 to October 2004, respectively. The data were tested for two types of trends: (1) a monotonic trend to determine if concentrations of the chemical constituents were generally decreasing, increasing, or stable during the study period, and (2) a step trend to determine if a change occurred following the December 1999-January 2000 forest thinning. Both parametric and non-parametric statistical analyses were carried out in this study. although the study area is only 35 km away from the Pacific Ocean, bulk precipitation chemistry was also influenced by terrestrial sources to a large extent. Streamwater chemistry was influenced by bedrock weathering, which was dominated by Ca²⁺ and HCO3^-, and was not strongly related to precipitation chemistry. Non-parametric Seasonal Kendall Test (SKT) showed a decreasing trend of Ca²⁺ and an increasing trend of K⁺ in bulk precipitation. Despite the decreasing trend of Mg²⁺, an increasing trend of pH was found in the streamwater. non-parametric Mann-Whitney-Wilcoxon Rank Sum test showed statistically significant increases of NO3^- and Ca²⁺ in streamwater followed by a moderate thinning operation.

Keywords: biogeochemical process; forest stream; thinning; monotonic trend; step trend』

1. Introduction
2. Materials and methods
　2.1. Study area
　2.2. Field sampling procedures
　2.3. Laboratory analytical procedures
　2.4. Statistical and mathematical procedures
3. Results and discussion
　3.1. Bilk precipitation chemistry
　3.2. Streamwater chemistry
　3.3. Impact of thinning on streamwater chemistry
4. Conclusions
References