旱季不同土地利用类型下岩溶碳汇效应差异

为研究不同土地利用类型下碳酸盐岩溶蚀对土壤CO2消耗量的差异,在2013年11月至2014年5月选取了柏树湾泉、兰花沟泉和后沟泉这3个岩溶泉进行水化学分析及野外监测.结果表明,在上覆植被为林地的柏树湾泉域,泉水的HCO-3浓度最高,草地与耕地下的兰花沟泉次之,耕地为主的后沟泉最低.柏树湾泉的HCO-3主要来自于碳酸对碳酸盐岩的溶蚀,Ca2++Mg2+与HCO-3的摩尔比接近0.5,而兰花沟泉和后沟泉的HCO-3则主要来源于硫酸和硝酸对碳酸盐岩的溶蚀,Ca2++Mg2+与HCO-3的摩尔比远远大于0.5.柏树湾泉域由于凋落物的输入以及土壤透气性差,土壤CO2更容易溶于下渗水并与碳酸盐岩反应,而兰花沟泉和后沟泉的耕地由于土壤疏松,土壤CO2更容易以土壤呼吸的形式返回到大气中.因此,为准确评估岩溶碳汇作用,需要研究不同土地利用类型下碳酸盐岩对CO2消耗量的差异.

Difference of Karst Carbon Sink Under Different Land Use and Land Cover Areas in Dry Season

In order to identify the distinction of soil CO₂ consumed by carbonate rock dissolution, Baishuwan spring, Lanhuagou spring and Hougou spring were selected as objects to monitor the hydrochemistry from November 2013 to May 2014. The results showed that the highest HCO₃^- concentration was observed in Baishuwan spring which is covered by pine forest, while the lowest HCO₃^- concentration was observed in Hougou spring which is mainly covered by cultivated land. In Baishuwan spring, HCO₃^- was mainly derived from carbonic acid dissolving carbonate rock and the molar ratio between Ca²⁺+Mg²⁺ and HCO₃^- was close to 0.5; while the molar ratio between Ca²⁺+Mg²⁺ and HCO₃^- exceeded 0.5 because the carbonate rock in Lanhuagou spring and Hougou spring was mainly dissolved by nitric acid and sulfuric acid. Because of the input of litter and the fact that gas-permeability of soil was limited in Baishuwan spring catchment, most of soil CO₂ was dissolved in infiltrated water and reacted with bedrock. However, in Lanhuagou spring catchment and Hougou spring catchment, porous soil made soil CO₂ easier to return to the atmosphere in the form of soil respiration. Therefore, in order to accurately estimate karst carbon sink, it was required to clarify the distinction of CO₂ consumption by carbonate rock dissolution under different land use and land cover areas.