文中研究了中国科学院环江喀斯特农业生态系统观测站内的地表水（地表径流和溪流）中溶解性有机碳（DOC）和溶解性无机碳（DIC）及其同位素组成在两次降雨事件中的连续变化特征。在两次降雨中DOC和DIC输移量分别为107．1和812．5kg，分别约为无降雨条件下相同时间内IX）C和DIC输移量的64和8倍。降雨时洼地溪流下游出口处水体中的DOC主要来源于雨水垂直入渗过程，其比例占到了60％～81％，源于地表径流冲刷的比例相对较低。利用溶解无机碳同位素（δ^13CDIC）估算了不同水体中土壤有机质分解对水中DIC的贡献（PSOC），其中地表径流、溪流上游和溪流下游出口水体的PSOC变化范围分别为56％～61％、56％～63％和50％～58％。两次降雨过程中约有459．6k土壤CO2进入溪流下游出口水体，而未降雨条件下在相同时间内只有48．3kg。降雨对喀斯特集水区溶解性碳的循环产生显著影响，对喀斯特集水区不同时间尺度碳循环的研究可以获得更为准确的区域碳及其他养分循环的信息。%Continuous samplings of surface water, including stream flow and surface flow, catchment （Huanjiang Karst Agricultural Ecological Station, Chinese Academy of Sciences） were conducted during two rainfall events on Aug. 23 and Aug. 24, 2007, with the main purpose of understanding the responses of dissolved carbon （DOC and DIC） and stable carbon isotopic composition of DIC （δ^13CDIC ） to the rainfall. Both the dissolved carbon concentrations and δ^13CDIC values varied quickly in response to the rainfalls. About 107.1 kg of DOC and 812.5 kg of DIC were transported out of the catchment during two rainfall events, about 64 and 8 times respectively those of normal days during the same period. According to δ^13CDIC values of the water, about 56%- 61%, 56%- 63%,and 50%- 58% of DIC in surface flow, upstream flow and downstream flow, respectively, were estimated to be originated from soil COz. About 406.2 kg soil CO2 was dissolved in downstream water during rainfall periods, while the amount during the same period of normal days was only about 48. 3 kg. It is concluded that rainfall can significantly affect the carbon cycling of the catchment, and the studies of cycling of carbon and other nutrients on different time scales and rainfall events are important for understanding local and global carbon cycling.
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