Studies on budget of water vapor and carbon dioxide in Rasyomon doline

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Micrometeorological factors( such as air temperature, humidity, air flow, and photosynthesis available radiation) and physiological factors of plants ( such as photosynthesis and transpiration rates) were measured in Rasyomon doline. At the lowest point in the doline, erosion created a weak breathing, blowing cavetunnel, draining a cold air in warmer seasons. The bottom in the depression was characterized by daytime summer temperatures below about 15ﾟC.Throughout warm seasons, very stable thermal layer was formed in the doline and it maintained a perhumid climate, which was a favorite environment to mosses.To clarify how the air flow from the cave relates to the drying in the doline, we artificially closed the narrowest section of the cave 2 times in the summer of 1997. Air temperature and soil temperature were higher by 3-4ﾟC in the closed period than in the opened period of cave. However, water, vapor increased by 4-5 hPa in the closed period than that in the opened period. The CO_2 concentration were about 700 ppm in the opened period and increased high levels near 1000 ppm in the closed period of cave. These results demonstrate quantitatively that the strengthned air with a cool but dehumified air is closely related to drying of the doline. The closure of cave also induced a significant rise of CO_2 concentration at the bottom of the doline, which is a favorite environment for mosses to grow. Considering these results, we are now planning to reduce an air flow through the cave to prevent from drying of caveand to renew the moss forest. Most of plants growing at the bottom of the doline had physiological charactersitics of shade plant, adopting to the specific environment of doline.