鼎湖山不同演替阶段土壤酸性阳离子淋溶动态研究

 采用室内土柱模拟实验，对鼎湖山不同演替阶段(演替早期的针叶林、演替中期的混交林和演替后期的阔叶林)森林土壤酸性阳离子的淋溶动态及机理进行研究。结果表明，土壤滤出液酸性阳离子的释放浓度及电导率(EC)与土壤所处的演替阶段密切相关，即与本底值密切相关。随着模拟酸雨处理时间的增加，滤液EC呈下降趋势，pH逐渐上升，在淋溶的第6天略有下降，且滤液pH和EC呈极显著负相关(P< 0.001;R= -0.81)。滤液中H⁺浓度及EC变幅均以演替早期针叶林最大，混交林最小。各演替阶段土壤Al³⁺溶出随着淋溶时间的延长迅速下降，但在第6天有进一步被活化的趋势。针叶林和混交林Fe³⁺和Mn²⁺比较相似的释放；而阔叶林则较为复杂。与模拟酸雨的酸度相比，离子的浓度对测定指标起着更重要的作用。对不同演替阶段土壤酸性阳离子的释放动态分析表明，各演替阶段土壤均处于铝氧化物缓冲阶段；同时，演替后期阔叶林土壤还处于铁氧化物和锰氧化物(氢氧化物)缓冲阶段。

Release of Acidic Cations by Simulated Acid Rain from Different Successional Stage Soils in Dinghushan

The dynamics of acidic cations by simulated acid rain from different successional stage soils (Pine forest (PMF), Pine broadleaf mixed forest (PBMF) and Monsoon evergreen broadleaf forest (MEBF), belonging to the early, the medium and the later stage, respectively ) were studied. Results showed there was a close relationship between leaching concentration of each acidic cation and the soil characteristics.pH values of leachate increased with leaching, but opposite in EC. The change extent of H⁺ and EC was biggest in PMF while least in PBMF. In each soil, the concentrations of Al³⁺ of leachate decreased rapidly as simulated acid leaching, while increased in the later leaching period. The leaching dynamics of Fe³⁺ and Mn²⁺ were similar in PMF and PBMF, but which were more complexity in MEBF. Generally, simulated acid rain with lower or medium concentration of balances ions in pH 4.5 could favor to reduce the acidic cations releasing and leachate acidity, but intensified as higher balance ions addition. Analyzed from the released dynamic of acidic caitons from different successional stage soils, all of the soil belonged to the Al oxid compound buffer stage, whereas soil in later successional stage also belonged to the Fe and Mn oxid buffer stages.