Abstract
On coral islands, Kikai and Miyako Islands in Japan, where intensive agriculture is developed and ammonium sulfate is extensively spread, we discussed the difference of carbonate dissolution and CO2 emission between the forest and the agricultural areas using fertilizer, groundwater, and CO2 data in spring sites. In the agricultural area, higher CO2 concentrations were detected, which were thought to be mainly caused in the carbonate dissolution accelerated by H＋ produced in nitrification of ammonia from ammonium sulfate and the decline of acid neutralizing capacity due to NO3－ and SO42－ deriving from the fertilizer. Carbonate dissolution rate in the agricultural area was estimated to be 1.7 times in average and 2.3 times at maximum as compared to the forest area. Carbon emission in the agricultural area was also estimated to be 27.4 and 15.8 tC km－2 y－1 in Kikai and Miyako Islands, respectively.
