喀斯特森林群落退化对浅层岩溶地下水化学的影响

对贵州中部喀斯特地区植被调查及径流和岩溶水样分析,探讨喀斯特森林群落退化过程中浅层岩溶地下水化学组成的变化.结果表明:喀斯特森林生态系统降雨中离子浓度大小的排序为SO2-4＞K 、Ca2 、HCO3-＞Na 、Mg2 、Cl-＞NO3-、NH4 ＞PO3-4,而径流中离子浓度的大小排序为HCO3-＞SO2-4、Ca2 ＞Mg2 、Cl-＞K 、Na 、NO3-＞NH4 ＞PO34-;岩溶地下水离子组成与径流总体相似,但岩溶地下水中HCO3-、Ca2 和Mg2 的含量及电导率明显增加高于地表径流.随着喀斯特森林群落从阔叶林群落向灌木林群落、灌草群落方向演替,其岩溶地下水中HCO3-和Ca2 比例明显减少,而SO2-4比例明显增加.岩溶地下水的HCO3-、Ca2 含量与森林覆盖率之间存在显著的正相关,而K 、NH4 含量与森林覆盖率之间则存在显著的负相关.HCO3-含量是影响岩溶地下水电导率的最重要因子,其次是Ca2 ,再次是K 、Mg2 ;岩溶地下水电导率可以作为评价喀斯特森林群落退化对生态环境影响的数量指标.

Effects of Forest Community Degradation on Water Chemical of Karst Shallow Groundwater

The effects of forest community degradation on chemical composition of Karst shallow groundwater were studied in Guizhou Province by investigating vegetations and analyzing the samples of runoff and Karst groundwater. The results showed that the order of concentrations of anion and cation in rainfall is SO~ 2- _4> K~+, Ca~ 2+ , HCO~-_3> Na~+, Mg~ 2+ , Cl~->NO~-_3, NH~+_4> PO~3-_4, while the order of concentrations of anion and cation in runoff is HCO~-_3> SO~ 2- _4, Ca~ 2+ > Mg~ 2+ , Cl~-> K~+, Na~+, NO~-_3> NH~+_4> PO~ 3- _4, and that the chemical composition of Karst shallow groundwater is similar with that of the runoff, but the concentrations of HCO~-_3, Ca~ 2+ , Mg~ 2+ and electric conductivity are higher than that of surface runoff. The results also showed that with increasing the grades of Karst forest community degradation, the percents of HCO~-_3, Ca~ 2+ reduced significantly and the percent of SO~ 2- _4 enhanced obviously, and that the contents of HCO~-_3, Ca~ 2+ , K~+, NH~+_4 in Karst shallow groundwater correlated significantly with the rate of forest coverage, which the content of HCO~-_3 is dominant factor to impact on electric conductivity of Karst groundwater, Ca~2+ , K~+ and Mg~2+ coming next,so that electric conductivity could be used as primary indices to evaluate Karst forest community degradation impacting on ecological environment.