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.