Effects Of Different Transformation Measures On Soil Organic Carbon In The Pinus Massoniana Low-Benefit Forest In Southern Sichuan

The research object of this study is to study the low efficiency forest in the south of Sichuan Province, and set up six processing modes.A control forest (CK). all down reconstruction and 4 kinds of gaps.The gaps are L1 (10m×10m), L2 (20m×20m).L3 (30m×30m).L4 (40m X 40m).In this paper, the effects of different measures on soil organic carbon and nitrogen characteristics.active organic carbon fractions(Readily oxidized organic carbon, Dissolved organic carbon. Particulate organic carbon),Soil carbon and nitrogen ratio,Oxidation stability,forest soil humus and seasonal variation were studied, and the correlation between soil organic carbon and other organic carbon fractions was analyzed.The main results were as follows.(1) Low efficiency forest was transformed after 3 years, the content of soil organic carbon in 5 measures decreased by 9.63%-46.37%.The soil organic carbon content showed the trend of decreasing with the increase of soil layer.The surface (0-20cm) SOC content was significantly higher than that of the sub surface layer (20-40cm),the organic carbon content of the surface gathering in obvious.In the whole soil profile,the organic carbon content is approximately expressed as the control forest>small gaps>big gaps>all down reconstruction.Different measures have significant difference with the control of CK (P<0.05).The study showed that the early stage of the transformation of low efficiency forest of Pinus. reduced the content of organic carbon in forest land, and increased with the increase of the area and intensity of artificial disturbance.(2) After the transformation of low efficiency forest,The soil total nitrogen (TN) content showed a trend of decreasing with the increasing of the artificial disturbance area.Surface (0-20cm) TN content was significantly higher than that of the sub surface layer (20-40cm).The trend of TN content in soil was CK>Ll>L2>L3>L4>QK.The soil C/N was increased first and then decreased trend in soil.L2 (20m × 20m) gap is the highest in the transformation of soil C/N.The gap area is very important for forest transformation and stability of organic carbon.(3) Readily oxidized organic carbon (ROC) and paniculate organic carbon (POC) decreased with the increase of the area of the transformation,there were significant differences between different reform measures.The trend of dissolved organic carbon content (DOC) was first decreased and then increased.No significant differences between different measures (P>0.05).(4) The content of soil humus decreased with the increase of the artificial interference area in the low efficiency forest after the transformation.The content of humic acid (HA) and the content of fulvic acid (FA) and the change of total humus content were basically the same.The value of PQ (HA/humus) in L2 is the highest, the gap of 20*20 transformation of soil humus quality is relatively high.(5) Significant between SOC content and ROC, DOC, POC. HA and FA were correlated (P< 0.05).The results showed that the soil active organic carbon has a close relationship with different carbon fractions, and it is affected by the soil organic carbon to a certain extent.(6) The seasonal variation of SOC and the different components in different transformation measures of Pinus was basically the same.DOC showed higher in winter and spring than in summer and Autumn.The other performance for autumn and summer is higher than that in spring and winter.The results showed that the soil water and heal conditions were closely related to soil physical and chemical properties, microbial activity and carbon stability.To sum up, low efficiency forest was transformed after 3 years.the contents of soil organic carbon and the active carbon fractions decreased gradually.he proportion of different transformation measures to reduce the difference.The area of forest windows is closely related to the stability of organic carbon pool.The big gaps or full cut build will reduce the content of organic carbon and its stability.Therefore, it is very important to select a suitable area for the reconstruction of low efficiency forest.