岩溶生态系统中的碳循环特征与碳汇效应

碳酸盐岩是岩溶生态系统的物质基础,而碳酸盐岩的形成过程对大气CO2浓度的降低产生重要的作用,目前地球上99.5%的碳被封存在碳酸盐岩中;岩溶生态系统具有富钙、偏碱性的地球化学背景,制约其碳循环特征:碳酸盐岩是在清洁海洋环境中、以生物化学沉积为特征形成的沉积岩,其酸不溶物含量低,通常小于10%,意味着岩溶区土壤资源短缺,土壤总碳库量偏小,同时石灰土的富钙性导致石灰土缓效性碳库和惰性碳库大,土壤碳库的稳定性提高;土壤资源短缺,植被生长发育受到养分、水分的胁迫,使植被的地上、地下生物量的比例发生变化,岩溶区植被地上/地下生物量的比例可占30%～50%,高于非岩溶区的;岩溶水中的高HCO3-浓度,刺激水生植物的光合作用,并将无机碳转化为有机碳,提高碳迁移过程中的稳定性;本文的目的是根据最近的研究成果,揭示岩溶生态系统中碳酸盐岩-土壤-植被-水中碳赋存的状态和转化过程,提出促进岩溶碳汇效应的技术途径。

Characteristics of Carbon Cycle and the Effect of Carbon Sink in Karst Ecosystem

Carbonate rock is the basic material of karst ecosystem, and its formation in the geological era plays an important role in decreasing atmospheric CO₂, about 99.5% of carbon in the Earth is sealed in carbonate rocks; the karst ecosystem is characterized as being rich in calcium, alkaline, able to impact carbon cycle:carbonate rock is a type of sedimentary rock derived from clean ocean, its acidic insoluble matter is usually less than 10%, which leads to the shortage of soil resources in karst areas, therefore the total amount of limestone soil carbon in the karst areas is small. The high calcium makes more organic carbon stock in the shape of slow and recalcitrant carbon pools, and can improve the stability of limestone soil organic carbon. The proportion of underground biomass of vegetation in the karst areas may increase, because of the shortage of soil resources, nutrients and water resources, the ratios of underground/above vegetation biomass in the karst areas can be up to 30%~50%, higher than those in the non-karst areas. The high content of HCO₃^- in karst water stimulates the photosynthesis of aquatic plants, and inorganic carbon can be converted to organic carbon. This process would improve the stability of carbon in water flow. This paper tried to clarify the state, migration and transformation of carbon at the interface of carbonate rock-soil-vegetation-atmosphere-water system in the karst ecosystem, meanwhile the approaches were put forward to promote karst processes and carbon sequestration.