Variations in soil carbon, nitrogen, phosphorus and stoichiometry along forest succession in southern China

Abstract. Floristic composition changes during forest succession influence nutrient cycling. However, variation patterns of soil carbon (C), nitrogen (N), and phosphorous (P), and soil stoichiometry (C : N, C : P, and N : P ratios) along forest succession are controversial. In this study, soil samples were collected at depths of 0–10, 10–20, and 20–30 cm in three forests at early, middle, and late succession stages. Concentrations of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) were measured. As succession proceeds, concentrations and storage of SOC and TN exhibited a significant increasing tendency, while those of TP decreased significantly. The tendency was more pronounced (P < 0.05) in soil depths of 0–10 cm, implying that more SOC, TN, and TP were stored in the upper soil layer. The ratios of soil C : P and N : P increased far more than the C : N ratio with succession progress, indicating that forests in this region were primarily limited by P over time. The C : N, C : P, and N : P ratios decreased from the upper to lower soil layers at almost all succession stages. A significantly positive correlation was found between the SOC, TN, and TP concentrations (P < 0.05), implying a relatively constrained C : N : P ratio in this subtropical forest soil. Stand density, litter, soil bulk density, pH, texture, and elevation significantly affected SOC, TN, and TP concentrations and their storage. The effects of succession stage, stand density, soil depth, and soil properties on soil nutrient balance should be considered in future studies.