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.