| Research Abstract |
Weight loss of limestone tablets by solution has been measured in order to clarify the regionality and year to year fluctuation of the karst processes at 7 observation stations (Asahikawa, abukuma, Chichibu, Akiyoshidai, Sikoku-onogahara, Ryugado and Minamidaito) in Japan during 1993-1997. This study was supported by Grant-in-aid in 1995,1996, and 1997. The results obtained are as follows :
(1) In Honshu, solution rates are higher in the southern parts of Japan. However, Minamidaito is an exception, because of existence of dry period during summer.
(2) In each station, the solution rates in A_3 and B_2 horizon of soil layrs are 2-3 times higher than 1.5m in the air above the ground. This means that the "covered karst processes" are 2-3 times higher than the "bare karst processes".
(3) During the 5 years measured, the highest solution rates were occurred in 1993, a wet year and on the contrary, the smallest solution rates were occurred in 1994, a dry and hot year, which appeared at the almost all observation points.
(4) Correlation coefficient between (solution rate of limestone) and (water surplus, WS-water deficit, WD) for the 5 years is the highest in the air, 1.5m above the ground.
(5) Correlation coefficient between (solution rate of limestone in A_3 horizon and B_2 horizon of soils) and (annual precipitation) is the highest for the 5 years measured.
(6) In the soils, high CO_2 contents have been observed during the warmer period of the years. After 3-4 days of 20mm rainfall, CO_2 contents in the soils show extremely high value. It is considered that these water contents and high CO_2 values resulted in karstification strongly.
In conclusion, the systematization of karst processes in Japan has been made clear as written in (1)-(6) above.
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