不同植被类型覆盖下土壤CO_2浓度对洞穴景观的影响

The impact of the soil CO_2 concentration under different types of vegetation on landscape in caves

土壤中的CO2 通过影响土壤水对碳酸盐岩的溶蚀能力控制洞穴滴水中的Ca2 +初始含量 ,同时它进入洞穴水体后溶解度的变化也会影响洞穴景观的形成。研究表明 ,不同植被类型对土壤CO2 浓度会产生不同影响。本文通过模拟分析认为 ,在一定范围内 ,地表生态系统的改善有利于土壤中CO2 的增加和洞穴中碳酸钙沉积景观的发育 ,但是若超过一定的阈值 ,即土壤中的CO2 浓度过高 ,使喀斯特水中的CO2 不能在洞穴顶部碳酸盐岩体渗流过程中完全被消耗时 ,洞穴滴水的酸性会对碳酸钙产生溶蚀作用 ,易形成洞穴溶蚀景观。

By analyzing the forming process of the cave landscape the authors think that the change of the CO 2 solubility in the water entering into the cave is vital to the formation of the cave landscape.And the temperature and partial pressure of CO 2 are the key elements to play the role on it. Calculation indicates that when the cave air CO 2 concentration is within 1800ppm the latter is the most important element to the landscape formation. The soil CO 2 is the major source of CO 2 in the cave water: Firstly it facilitates the formation of the soil water into carbonic acid water and when the water contacts with the carbonate rock above the cave the solution chemical reaction will happen. This action will provide the Ca 2+ for the cave sediments. Secondly the soil CO 2 concentration will affect the CO 2 concentration directly in the cave water. From the experts' views the soil CO 2 mainly comes from the respiration of the vegetation the amount of the microorganism and the atmosphere outside the cave. Our field work also indicates that vegetation is one of the most important elements that control the soil CO 2 concentration and its distribution. We do the research in the Yaolin cave by comparing the effect of different CO 2 concentrations to simulate the different CO 2 concentrations under different types of vegetation dealing with the cave landscape. The conclusion is that when the soil CO 2 concentration is higher it will be good to the cave landscape protection and development.That is to say the cave landscape covered by the vegetation is much better than the one covered poorly. But if the CO 2 concentration is too high the soil CO 2 can filter into the cave through rock slot and make the cave water keep the acid character to dissolve the old landscape sediments and the dissolved views are formed.