【摘要】 于2007年9月—2009年8月对中国西南茂兰喀斯特地区亚热带常绿落叶阔叶混交林大气降水、林冠穿透雨和树干茎流进行观测,分析了各降水分配中的养分离子(Ca2+、Mg2+、K+、Na+、NH4+、SO42-、NO3-、Cl-)浓度动态变化规律及年养分元素输入量。结果表明:7—9月,林外雨、林冠穿透雨和树干茎流中各养分离子浓度相对较低,12月—翌年2月,各降水分配中各养分离子浓度相对较高;降水通过林冠或树干后,除了Na+浓度无显著变化外,NH4+浓度表现下降趋势,Ca2+、Mg2+、K+、Cl-、NO3-和SO42-均表现增加趋势;林外雨的养分元素输入量顺序为Ca2+>SO42--S>NH4+-N>Cl->K+>Na+>Mg2+>NO3--N。在林冠穿透雨+树干茎流中的养分元素输入量顺序为K+>Ca2+>Cl->SO42--S>Mg2+>NH4+-N>NO3--N>Na+。与非喀斯特地区相比,林外雨中的各养分离子浓度较低,林冠穿透雨、树干茎流中的K+、Ca2+、Mg2+增加幅度较大。总体来看,独特的立地特征决定了该地区Ca2+、Mg2+的积极参与生态系统养分循环和K+高效循环的特征。更多还原

【Abstract】 Precipitation,throughfall,and stemflow were collected during the period of September,2007 to August,2009 from a subtropical natural evergreen and deciduous broadleaf mixed forest in Maolan,a karst area in Southwest China. The concentrations of major ions( Ca2 +,Mg2 +,K+,Na+,NH4+,SO42-,NO3-,Cl-) were determined for collected samples in order to quantify the annual amounts of major nutrient elements and to examine changes in chemical composition of precipitation after passing through the canopy. The results showed that:( 1) the concentrations of the major nutrient ions in precipitation,throughfall and stemflow were lower during the summer( from July to September),but higher in the winter( from December to the following February);( 2) compared with precipitation,the concentrations of Ca2 +,Mg2 +,K+,Cl-,NO3-,and SO42-in throughfall and stemflow increased obviously,while there was a decrease in NH4+concentration and no significant variation in Na+concentration;( 3) the annual inputs of nutrient ions via precipitation were in order of Ca2 +> SO42-> NH4+-N > Cl-> K+>Na+> Mg2 +> NO3--N,and the annual inputs of nutrient elements via throughfall plus stemflow were in order of Ca2 +> SO42--S > NH4+-N > Cl-> K+> Na+> Mg2 +> NO3--N. Compared with non-karst areas,low ion concentrations in local precipitation demonstrated less anthropogenic influences on the studied forests,while the concentrations of K+,Ca2 +and Mg2 +in throughfall and stemflow increased greatly. Our study showed that K+,Ca2 +and Mg2 +mainly derived from carbonate weathering were active in the hydrologic cycling of nutrients in karst forests.更多还原