Reconstraction of Limestone Solution Model in Japan

对日本旭川、武间、秋吉台、四国、琉球和南中台岛6个站点近10年的溶解度进行了观测。土壤B_2层10年总溶解速率均高于地面以上1.5 m的空气。特别是秋吉台和南中台的B_2层总溶解率极高，约为12%。这些数值大约是空气中数值的4倍。溶解率的年际波动也很大。当缺水程度高时，溶液速率明显较低。在干旱年份，B_2层的溶解率仅为空气中的2倍。同时对各站点10年土壤CO_2含量进行了测定。水分亏缺高时，土壤中CO_2含量变得非常小。然而，在一天降雨量达到20 mm后，CO_2含量变得非常高。因此，土壤水分平衡的年际波动反映了土壤溶解速率的年际波动。在Minamidaito，隆起的环礁，古喀斯特地形可以用来计算年龄，因为该岛变成隆起的时间。即利用溶蚀速率，利用时间与古水量平衡的关系，得到岩溶地形的形成模式。

Solution rate of the limestone tablets during the last 10 years were observed at the six stations (Asahikawa, Abukuma, Akiyoshidai, Shikoku, Ryugado and Minamidaito Island) in Japan. The 10 years total solution, rates were higher in B_2 horizon of soil than in the air 1.5 m above the ground at all stations. Especially, the total solution rates in B_2 horizon are extremely high at Akiyoshidai and Minamidaito: about 12 %. These values are roughly 4 times higher than these in the air.Inter-annual fluctuation of solution rates was also very large. When water deficits are high, the solution rates are clearly low. In a dry year, the solution rate in B_2 horizon is only 2 times higher than in the air.The CO_2 contents in soil were also examined at the all stations in 10 years. When water deficit is high, CO_2 content in soils becomes very small. However, after rainfall of 20 mm in a day, CO_2 content becomes extremely high. It is, therefore indicated that inter-annual fluctuation of solution rate is reflected by inter-annual fluctuation of water balance in soils.In Minamidaito, where is uplifted atoll, palaeo karst terrain can be used for calculation of ages, since the time when the island changed to uplift. That is, using solution rate, the formation model of karst terrain can be obtained, making use of relationship between time and palaeo water balance.