Abstract: To elucidate the regulatory effects of decaying coarse woody debris on soil carbon and nutrient balance, we measured soil organic carbon, nitrogen, and phosphorus contents and stoichiometric ratios in the topsoil (0-10 cm) beneath Minjiang fir (Abies faxoniana) coarse woody debris of decay classes Ⅰ-Ⅴ, with diameter of 10-30 cm and 30-50 cm in a subalpine coniferous forest. Areas without coarse woody debris situated at least 1 m away from the debris were set as control. The results showed that decaying coarse woody debris significantly increased contents of soil organic carbon (114.1%-412.2%) and nitrogen (0.1%-198.0%), as well as C/N (61.7%-117.1%), C/P (379.6%-931.1%) and N/P (206.3%-532.6%) in soils, but significantly udecreased soil phosphorus content by 28.1%-70.9%. The effects of coarse woody debris on soil organic carbon, nitrogen, and phosphorus content varied with decay classes and diameters. The content of organic carbon and nitrogen in soils beneath large diameter coarse woody debris at decay classes Ⅲ and Ⅳ were significantly higher than those beneath coarse woody debris with small diameter. Soil phosphorus content beneath large diameter coarse woody debris at decay class Ⅲ was significantly higher than that beneath small diameter. Moreover, ecological stoichiometric ratios in soils beneath large diameter coarse woody debris exhibited significant correlations with organic carbon, nitrogen, and phosphorus content of coarse woody debris. In conclusion, retaining larger diameter coarse woody debris with medium to highly decayed classes on the forest floor is beneficial for soil nutrient balance.

Key words: Abies faxoniana, coarse woody debris, soil nutrient, ecological stoichiometric ratio