Effects of Drought on the C/N/P Stoichiometry in the Soil of a Subtropical Monsoon Evergreen Broad-leaved Forest

In order to investigate the effects of drought on soil carbon (C), nitrogen (N) and phosphorus (P), this study was conducted to analyze soil C, N and P content of a subtropical monsoon evergreen broad-leaved forest in the Dinghushan Natural Reserve, with manmade precipitation pattern manipulations. The studied forest is the climax forest in southern China but most sensitive to environmental changes, and therefore important to the stabilization of climate system in this region. A treatment to remove 50% of annual precipitation was conducted for 2 years in the studied forest, with natural precipitation as the control. Results showed that compared with the control, the drought treatment significantly reduced soil moisture. Soil C, N and P content of the subtropical monsoon evergreen broad-leaved forest gradually decreased with the increase of soil depth. Soil C and P content tended to increase but soil N content did not change obviously under the drought treatment in relative to the control. The C : N, C : P and N : P of the subtropical monsoon evergreen broad-leaved forest decreased with the increasing of the soil depth. Detectable increases in soil C : N and C : P ratios but a decrease in soil (0-10 cm) N : P ratio induced by the drought treatment. Our results suggest that a 2-year-period precipitation decrease can significantly reduce soil moisture and therefore decrease the decomposition rate of soil organic matter, change the accumulations of soil C, N and P in the subtropical climax forest of southern China.