[Effects of soil moisture on litter decomposition of three main tree species in Northeast China.]

The effects of soil moisture variation on the litter decomposition of main tree species Betula platyphylla, Abies nephrolepis and Pinus koraiensis were evaluated in a primary forest of Korean pine (P. koraiensis) in Fenglin National Nature Reserve of the Northeast China, based on the measurements of surface (0-10 cm) soil moisture from 1998 to 2017. The results showed that litter decomposition rates increased with the increase of litter quality. The order of litter decomposition rate was B. platyphylla > A. nephrolepis > P. koraiensis at the same soil moisture. The litter decomposition rates decreased with the decrease of soil moisture. The sensitivity index of litter decomposition rates on soil moisture (M₁₀) were 0.782, 0.789 and 0.827, respectively, for B. platyphylla, A. nephrolepis and P. koraiensis. The initial litter decomposition rate decreased by 21.8%, 21.1% and 17.3% for B. platyphylla, A. nephrolepis and P. koraiensis, respectively, when soil moisture decreased by 10%. The decomposition rates of high-quality litter (high nitrogen content, low carbon to nitrogen ratio, and low lignin content) were more sensitive to the variation of soil moisture. The difference in decomposition rate among different litter types was reduced with the decrease of soil moisture. In the recent 20 years, the average soil moisture presented a significantly decreasing trend, which would inhibit litter decomposition in the primary Korean pine forest. Under the scena-rios of global change, soil moisture would further decrease with the increase of air temperature. It would definitely intensify the inhibitory effect on litter decomposition, and partly offset the enhanced effects of increased air temperature.