凋落物和根系输入对南亚热带季风常绿阔叶林土壤养分的影响

植被凋落物和根系输入在调节森林土壤元素生物地球化学循环中扮演着关键作用。目前仍然不清楚凋落物和根系输入对热带原始林土壤主要元素含量的调控作用。针对该研究现状，以中国南亚热带季风常绿阔叶林为研究对象，通过开展凋落物与根系输入改变的控制试验（6个处理，每处理4次重复：对照、凋落物加倍、凋落物去除、断根、断根+凋落物加倍、断根+去除凋落物），探讨了凋落物和断根处理对土壤可溶性离子、土壤酸中和能力（ANC）和阳离子交换量（CEC）的短期影响。凋落物与根系处理半年后的结果显示：（1）凋落物去除与加倍处理都显著增加了0-40 cm土壤NO₃^-含量，并且凋落物去除效应大于添加效应；去除凋落物增加了表层土壤（0-20 cm） Ca²⁺、Mg²⁺、Na⁺的含量。（2）断根处理显著增加0-40 cm土壤NO₃^-和表层土壤Ca²⁺、Mg²⁺含量。（3）断根和去除凋落物交互处理显著增加了0-40 cm土壤NO₃^-和表层土壤Ca²⁺、Mg²⁺、K⁺含量，产生了叠加效应。（4）凋落物和断根处理并没有改变土壤pH，但降低了土壤酸中和能力（除凋落物加倍外），其降低的原因主要与阳离子交换量的降低和NO₃^-含量的增加有关。这些结果表明，土壤养分离子的可利用性（尤其是NO₃^-和Ca²⁺、Mg²⁺）和酸缓冲能力对凋落物和根系输入改变响应敏感，森林植物及其凋落物对土壤养分保留和缓冲性能具有重要调节作用。在人为干扰和气候变化加剧背景下，该研究可为森林生态系统可持续管理提供重要的理论参考。此外，植被凋落物和根系输入改变引起的长期生态学效应仍值得进一步关注。

Short-term effects of altered litter and root inputs on soil water-extractable ions in a subtropical monsoon evergreen broadleaf forest, Southern China

Plant litter and root inputs play a key role in regulating soil biogeochemical cycles in forest ecosystems. However, it remains unclear how the alterations in litter aboveground litter inputs and belowground root inputs affect soil nutrients in the primary tropical forests or the intact tropical forests. This study aimed to investigate the impact of alterations in plant litter and root inputs on soil extractable cations and anions, acid neutralizing capacity (ANC) and cation exchange capacity (CEC), through the field litter- and root-manipulation experiment in a monsoon evergreen broadleaf forest at Dinghushan Biosphere Reserve of Southern China. The manipulation experiment consisted of six treatments, with four replications per treatment:Control (no change in both litter and root inputs), Double litter, Litter removal (No Litter), Root pruning (exclusion of root ingrowth), Root pruning+Double litter, Root pruning+Litter removal. After a half year of litter- and root-manipulations, the results of the experiment were as follows. (1) Litter removal and double litter treatments significantly increased soil NO₃^- concentration in the 0-40 cm layer, with higher values in the litter removal treatment than that in the double litter treatment, while litter removal treatment greatly increased soil concentrations of Ca²⁺, Mg²⁺ and Na⁺ in the surface 0-20 cm layer. (2) Root pruning treatment significantly increased soil NO₃^- concentration in all layers and soil Ca²⁺ and Mg²⁺ concentrations in the surface 0-20 cm layer. (3) The interactive effect of root pruning and litter removal treatments significantly increased soil NO₃^- concentrations in all soil layers, and Ca²⁺, Mg²⁺ and K⁺ concentrations in the surface 0-20 cm layer, causing an additive effect. (4) Litter and root manipulations did not alter soil pH, but decreased soil acid neutralizing capacity in all plots except the double litter treatment. The decreased acid neutralizing capacity was attributed to the decreased soil cation exchange capacity and the increased soil NO₃^- concentration. These findings suggest that short-term alterations in plant litter and root inputs can strongly affect soil nutrient availability (especially for NO₃^-, Ca²⁺ and Mg²⁺) and acid neutralizing capacity, thereby regulating soil nutrient retention and buffering capacity in forest ecosystems. Under the conditions of intensive human activities and climate change, this study can provide a valuable theoretical guideline for the sustainable management of forest ecosystem. And it merits further study to explore the long-term ecological consequences induced by changes in plant aboveground litter inputs and belowground root inputs into forest ecosystem.