岩溶地区土壤溶解有机碳的季节动态及环境效应

Seasonal changes of dissolved organic carbon in soil: its environmental implication in karst area

对桂林岩溶试验场土壤溶解有机碳(DOC)进行了逐月的观测,结果显示DOC是岩溶生态系统中活跃的有机碳组分,在岩溶地区碳循环中发挥着重要的作用。一年中土壤DOC的变化特征表现为3个阶段:(1)3～7月,随气温升高、降雨量增加,土壤生物活性和新陈代谢能力极大提高,土壤溶解有机碳呈升高趋势;(2)8～11月,气温保持较高的水平,但降雨量偏低,土壤干燥,土壤微生物活性极大地减弱,土壤DOC质量分数全年最低;(3)12月至次年2月,随温度的降低,土壤生物活性逐渐降低,土壤DOC呈缓慢升高趋势,且与土壤微生物量碳之间存在互为消长的关系。土壤碳酸盐岩的溶蚀速率季节变化与土壤DOC之间存在负相关。文章还提出了岩溶地区土壤碳循环模式及DOC在其中的作用。

The role of dissolved organic carbon (DOC) in soil water (or moisture) in karst process is poorly understood. In a Guilin karst experimental site, the soil DOC was monthly collected and analysed with the TOC-V analyzer from SHIMADZU co., Japan. The results showed the DOC is the active carbon component and plays important role in soil carbon cycle in karst. The changes of soil DOC could be expressed 3 stages during the observation: (1) From March to July, the soil DOC gradually increased with the temperature, rainfall, the activities of soil organisms, and metabolism; (2) From August to November, the temperature was kept high, however, the rainwater was substantially reduced. The soil became very dry and the soil microorganisms’ activities greatly decreased. The concentration of DOC in soil solution was the lowest; (3) From December to February, both temperature and rainfall were low. The fluctuations of soil DOC, however, were increased, which normally related to the carbon of soil microorganism biomass. The seasonal erosion rates of limestone tablets beneath the soil were negatively correlated with soil DOC. Based on these results, a con-ceptual model of the carbon cycle and DOC role in karst was putted forward.