2023 Volume 22 Issue 2 Pages 51-72
From April 2000 to January 2005, we monitored the chemistry of rainfall, throughfall, stemflow, O layer leachate, soil-percolating water, seepage water, and stream water in the Yamashiro Experimental Forest (YMS) in southern Kyoto Prefecture, Japan. To clarify the characteristics of YMS water quality, comparison was made with the data in the Forest Atmospheric Deposition and Stream Chemistry Database (FASC-DB) of the Forestry and Forest Products Research Institute (FFPRI). Rainfall acidity, and inorganic nitrogen and non-sea salt sulfate levels in precipitation were the same in the YMS as those at monitoring sites nationwide. However, throughfall and stemflow had a higher pH and percentage of K+ in total cations at the YMS compared to other monitoring sites. Seasonal variations in pH and K+ concentration were observed in the throughfall; both were high during the foliated period and low during the defoliated period. The O layer leachate was acidic and had high concentrations of dissolved organic carbon (DOC), Ca 2+ , and NO 3 . Their concentrations were also high in the soil-percolating waters, and no decrease in DOC concentration with depth was observed. Compared to the other monitoring sites in the FFPRI, the stream water in the YMS had slightly higher electrical conductivity, and higher concentrations of NO3 - and other ions. We speculate that the dissolved constituents are concentrated by evapotranspiration in the YMS watershed due to its warm, low precipitation climate. The high NO3 - concentration may be related to the large supply of nitrogen compounds from the densely populated areas in the Kyoto–Osaka area, in addition to the supply of nitrogen from dead trees in the watershed.
