Effect of Thinning on Content and Storage of Carbon, Nitrogen and Phosphorus in Litter and Soil in Cunninghamia lanceolata Plantation

In 1996, improved Cunninghamia lanceolata families were afforested with density of 2500 individual/ha in Kaihua Forest Farm of Zhejiang province.Tendering was carried out 2 times/year in the first 3 years after planting.In 2003, the first thinning was implement and in 2010, the second thinning experiment was made with light intensity (18%), moderate intensity (32%) and control (no thinning) in sample plot of 20 m×20m with 3 repeats.Within sample plot, 5 quadrats were established.In 2017, litter and soil in different quadrat were collected for investigation.The results showed that litter biomass, carbon, nitrogen and phosphorus storages had no significant difference among different treatment.The storage of total soil organic carbon, readily oxidizable organic carbon, total phosphorus and available phosphorus showed the same.However, the storage of total and hydrolysable nitrogen in the plot with moderate intensity increased by 40.7% and 32.3%than that in the control.There was no significant difference of total and hydrolysable nitrogen between light thinning and the control.The C:N:P ratios in litter and soil had no significant difference among different thinning treatment, while the ratio of soil readily oxidizable organic carbon/hydrolysable nitrogen decreased with the increase of thinning intensity (from 50.1 to 35.9), and the ratio of hydrolysable nitrogen/available phosphorus increased with the thinning intensity (from 60.0 to 81.6).