Effect Of Thinning Intensity On Soil Carbon In Larix Gmelinii Plantation

Forty years larix gmelinii plantation was studied at Fenghuang Mountain Forest Farm in Heilongjiang Province. Larch plantation soil organic carbon (SOC) concentration, labile organic carbon (LOC) concentration, soil enzyme activity, litter carbon storage, soil respiration rate were investigated after twenty-seven years thinning, with three thinning intensity (control (CK),15% thinning intensity (T1),40% thinning intensity (T2)). The effects of different thinning treatments on Larch plantation soil sink were analyzed, and the influence mechanism of SOC concentration with different thinning treatments was discussed. The results showed:(1) Thinning promoted SOC concentration, only T1 treatment was significant (P<0.05). Each soil layer SOC storage were increased than CK, in August, after twenty-seven years thinning, T1 and T2 treatment processed 0 to 60 cm soil layer SOC storage by 22.45% (P>0.05) and 38.31% (P<0.05) respectively. T2 treatment promoted the surface layer (0-20 cm) SOC contention in June to October. Illustrate the T1 treatment is more advantageous to the SOC storage sequestration, T2 treatment improve the SOC contention.(2) LOC was increased after thinning. T2 treatment increased the soil surface (0-10 cm) of LOC contention in August. Readily oxidation carbon (ROC) contention significantly increased (P<0.05). T2 treatment increase microbial organic carbon (MOC) contention. T2 treatment significantly increased surface layer (0-20 cm) water-soluble organic carbon (WSOC) and ROC contention (P<0.05), but the contention of there were no significantly change in June to October (P>0.05).(3) T1 treatment improve the larch plantation in soil the soil sucrose and amylase activity, were higher than CK surface layer(0-10cm) by 19.79% and 83.08% respectively. With declining soil, soil enzyme activity of a downward trend. All treatment carbon activity in surface layer is the largest, and the all soil layer were:T2> T1> CK. With the increase of thinning intensity, carbon activity and carbon management index were increased. So 40% thinning intensity of T2 treatment was more beneficial to the improvement of the plantation productivity.(4) T1 treatment increased the forest litter, and promoted forest litter decomposition. Thinning could reduce the soil respiration rate. With the global warming, soil respiration rate increased after thinning is far less than CK. So thinning, especially 15% thinning intensity was more conducive to the sequestration of soil carbon.In conclusion,15% thinning intensity of T1 treatment by increasing litter carbon, added to the amount of input in the soil carbon substrates to increasing soil carbon input. At the same time, T1 treatment reduced the soil respiration rate, thus increasing SOC.40% thinning intensity of T2 treatment increased the LOC contention, improve the soil sucrose and amylase activity, significantly improve carbon library management index. So T2 treatment was more beneficial to the improvement of the plantation productivity.