中文摘要：

选取亚热带花岗岩区不同利用方式下的3个相邻小流域 （F：100% 森林；FA1：82% 森林 ＋ 18% 农田；FA2：76% 森林 ＋ 24% 农田），通过定期监测与分析雨水和径流水的元素组成，获得了流域尺度元素的降水输入与径流输出特征，在此基础上分析了元素收支平衡及其对土壤酸化的影响。结果表明：雨水中离子输入总量为181.74 kg/（hm2·a），夏季输入量约占全年输入量的45%，Ca2＋、Na＋ 和NH4＋ 约占阳离子输入总量的80%，SO42- 和NO3- 约占阴离子输入总量的74%。F、FA1和FA2流域径流水中离子输出总量分别为236.81，153.17和243.36 kg/（hm2·a），夏季输出量约占全年输出量的39% ~ 47%，Ca2＋ 和Na＋ 约占阳离子输出总量的81% ~ 86%，SO42- 和NO3- 约占阴离子输出总量的65% ~ 70%。降水和径流水的元素收支平衡表明，F、FA1和FA2流域中SO42-、NO3-、Cl-、NH4＋ 和H＋ 均表现为净输入，其中SO42- 的净滞留量最高，分别为13.7、30.43和20.49 kg/（hm2·a）；而Ca2＋、Mg2＋ 和Na＋ 均表现为净输出，其中Na＋的净输出量最高，分别为28.99、14.96和31.76 kg/（hm2·a）。F、FA1和FA2流域内酸雨直接输入的H＋ 为818 mol/（hm2·a），而流域内氮素转化产生的H＋分别为396、389和401 mol/（hm2·a），占H＋ 输入总量的32% ~ 33%。F、FA1和FA2流域的土壤酸化速率分别为996、1 069和1 035 mol/（hm2·a），表明即使不考虑农业施肥的情况下农林复合流域（FA1和FA2） 的土壤酸化速率仍高于森林流域（F）。

英文摘要：

The regional element budgets are primarily important to understand the function of ecosystems and to establish the corresponding management practices. This study takes three adjacent small watersheds （F：100% forest, FA1： 82% forest ＋ 18% farmland and FA2： 76% forest ＋ 24% farmland） with different land uses as the monitoring areas, which are located in the granitic region of subtropical China. Element inputs in rain water and outputs in stream water were detected and quantified from March of 2007 to February of 2010. The characteristics of element budgets at watershed scale and their effects on soil acidification were discussed. The results showed that the total ion input in the rain water was 181.74 kg/（hm2·a）, with the summer input accounting for 45%. Ca2＋, Na＋ and NH4＋ contributed 80%to the total Cation input while SO42- and NO3- contributed 74% to the total anion input, respectively. The total ion outputs in stream water of the three watersheds （F, FA1 and FA2） were respectively 236.81, 153.17 and 243.36 kg/（hm2·a）, with summer output accounting for 39%-47%. Ca2＋ and Na＋ contributed 81%-86%, to the total cation output while SO42- and NO3- contributed 65%-70% to the total anion output. The element budgets of the three watersheds （F, FA1 and FA2） based on precipitation input and stream output demonstrated that there was a net sink of SO42-, NO3-, Cl-, H＋and NH4＋, while a net source of Ca2＋, Mg2＋ and Na＋. SO42- showed the highest net retention, while Na＋ showed the highest net export. The net retention of SO42– in the three watersheds （F, FA1 and FA2） were 13.7, 30.43 and 20.49 kg/（hm2·a）, respectively, while the net exports of Na＋in the three watersheds （F, FA1 and FA2） were 28.99, 14.96 and 31.76 kg/（hm2·a）, respectively. H＋ input directly from acid rain was 818 mol/（hm2·a）, while H＋ production from nitrogen transformation in the three watersheds were 396, 389 and 401 mol/（hm2·a）, accounting for 32%-33% of the total H＋ i