Changes of Soil Water, Organic Matter, and Exchangeable Cations Along a Forest Successional Gradient in Southern China

Abstract

Information on the distribution patterns of soil water content (SWC), soil organic matter (SOM), and soil exchangeable cations (SEC) is important for managing forest ecosystems in a sustainable manner. This study investigated how SWC, SOM, and SEC were influenced in forests along a successional gradient, including a regional climax (monsoon evergreen broad-leaved forest, or MEBF), a transitional forest (coniferous and broad-leaved mixed forest, or MF), and a pioneer forest (coniferous Masson pine ( Pinus massoniana) forest, or MPF) of the Dinghushan Biosphere Reserve in the subtropical region of southern China. SWC, SOM, and SEC excluding Ca 2+ were found to increase in the soil during forest succession, being highest in the top soil layer (0 to 15 cm depth) except for Na +. The differences between soil layers were largest in MF. This finding also suggested that the nutrients were enriched in the topsoil when they became increasingly scarce in the soil. There were no significant differences ( P = 0.05) among SWC, SOM, and SEC. A linear, positive correlation was found between SWC and SOM. The correlation between SOM and cation exchange capacity (CEC) was statistically significant, which agreed with the theory that the most important factor determining SEC is SOM. The ratio of K + to Na + in the topsoil was about a half of that in the plants of each forest. MF had the lowest exchangeable Ca 2+ concentration among the three forests and Ca 2+:K + in MPF was two times higher than that in MF. Understanding the changes of SWC, SOM, and CEC during forest succession would be of great help in protecting all three forests in southern China.