Abstract: Clarifying ecological stoichiometry and dynamic characteristics of soil carbon, nitrogen and phosphorus helps to understand nutrient storage, supply capacity and nutrient limitation in forest soils, and provide important guidance for ecosystem restoration and conservation. Soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), pH value, soil temperature (ST), soil water content (SWC), mean annual precipitation (MAP), temperature (MAT) and humidity (MAH) of a subtropical evergreen broad-leaved forest were quantified for ten years. Analysis of variance, correlation, redundancy, variance decomposition and multiple linear regression analysis were used to explore the interannual variations and stability of soil organic carbon, total nitrogen and phosphorus, as well as their stoichiometric ratios and the effects of environmental factors. The results showed that the contents of SOC, TN, and TP were 15.37-21.21, 1.19-2.03, and 0.08-0.14 g·kg^-1 in the dry season, respectively, with great interannual variations (P<0.01). In the rainy season, the contents of SOC, TN, and TP were 24.44-28.50, 1.76-2.32, and 0.17-0.22 g·kg^-1, respectively, with great interannual variations of TP content (P<0.05). The ratio of C∶N was significantly higher in the rainy season than that in the dry season (P<0.01), while the ratios of C∶P and N∶P were significantly higher in the dry season than that in the rainy season (P<0.01). (2) In the dry season, TN was significantly positively correlated with ST, TP was significantly positively correlated with MAH, while N∶P ratio was significantly negatively associated with MAH. However, there were no significant correlations between environmental factors and SOC, TN and TP, and ecological stoichiometry in the rainy season. Overall, environmental factors had less effect on TN (interpretation rate 23%) than on TP (68%) and SOC (53%), and TN was more susceptible to pH (independent effect 1%). N∶P was more responsive to environmental change (32%) than C∶N (14%) and C∶P (23%). (3) In the dry season, MAT (general dominance value 28.9%), ST (61.2%), and MAH (46.2%) were the dominant factors affecting SOC, TN, and TP content, respectively. Nevertheless, MAT was the dominant factor affecting SOC (87.5%) and TN (48.8%), but MAH (31.27%) was the key factor driving TP in the wet season. (4) The trend of interannual stability was as follows: N∶P>TP>C∶P>SOC>C∶N>TN. Moreover, the stability of SOC (40.0%) and TP (47.5%) was affected by MAP, while that of TN (47.9%) was affected by ST. In summary, the interannual variations of SOC, TN and TP contents were significantly affected by soil moisture limitation in the dry season, and the effect of environmental factors on TP was greater than on SOC and TN. Furthermore, temperature was the dominant environmental factor affecting SOC, TN and TP contents. The interannual stability of SOC and TP was mainly influenced by rainfall, while that of TN was driven by temperature.

Key words: evergreen broad-leaved forest, soil organic carbon, nitrogen and phosphorus, ecological stoichiometry, enviromental factor, homeostasis