| Biosphere in land is a huge carbon stock in which the balance of carbon in soils in forest ecosystems is a vital part of carbon cycling in globle and plays an irreplaceable role in retarding the growth of CO2.But uncertainty is still in existence.moreover the soil is the main source of this uncertainty.The slight change of SOC can notably influence the concentration of CO2 and indirectly influence the constitution of community and its physiological vigour as well as the construction, function and productivity of ecosystem through nutrient such as N,Pand K.At present the forest ecosystem in China has biggish function of reserving carbon on the whole.Recently the protection of wildwood and other forest ecological engineering have been carried out,but out-dated forest culture and management have led to some ecological residual problems.For instance, diversity of species is becoming scarce,soil is becoming vestigial,et.The artificial spruce forest in Miyaluo Forest Zone lies in alpestrine in west of Sichuan Province was chosen as object of study,and the influence on component of carbon in SOM(soil organic matter) in artificial spruce forest given by five intensity of intermediate cutting was compared so that reasonable disengagement cutting could be provided support of data with theoretical foundation in this article.Through the study of the content and seasonal variation of SOM and its active component in different forest zone,the result manifested:(1) Under different intensity of intermediate cutting,the content of SOC in soil layer of 0-10cm in artificial spruce forest was notably more than that of soil layer of 10-20cm(P <0.05).When intensity of intermediate cutting was 30%,SOC in each layer got to maximum.The variation trend embodied:F3> CK>F4>F1> F2;the variation trend of average content of 0-20cmTN in surface layer of soil embodied:F3> F4> F2> F1> CK;The C/N of soil in forest chosen as contrast was notably more than that of other forest zone of different intensity of intermediate cutting,the variation trend was:CK> F3> F1> F2> F4.The content of SOC and total nitrogen in soil layer of 0-20cm in each forest zone got to maximum in autumn.(2)Under different intensity of intermediate cutting.the difference between soluble organic carbon and nitrogen in soil in each forest zone was notable(P< 0.05).Concretely,when intensity of intermediate cutting was F1,F2,F3 and F4,DOC was 0.98,0.93,1.08 and 0.89 times as many as that of the forest chosen as contrast.DOC got to maximum when intensity of intermediate cutting was 30%.The content of DOC in soil layer of 10-20cm varied among 16.39～21.04mg/kg,the ratio of DOC occupied in SOC in each layer varied among 0.69%～0.81%;DON in soil layer of 0-10cm and 0-20cm varied among 4.81-5.49mg/kg and 4.39～5.03mg/kg; the ratio of DON occupied in total nitrogen in each layer varied among 1.55%～2.01% and gradually increased following the depth of soil layer.(3) Under different intensity of intermediate cutting,within soil layer of 0-20cm the average content of MBC embodied:CK (329.78 mg/kg)>F4 (311.06mg/kg)>F1 (306.67mg/kg)>F3 (301.31 mg/kg)>F2 (298.52mg/kg),of which MBC got to maximum in autumn and the change of average content was somewhat discriminative; the ratio of MBC occupied in SOC in soil layer of 0-20cm varied among 0.91%～1.16%.After intermediate cutting the turnaround time of MBC in soil in each forest zone could increase following the intensity of intermediate cutting.The turnround rate of MBC in forest chosen as contrast was 0.45 and 0.53a-1, and the turnaround time was 2.21 and 1.88a.When intensity of intermediate cutting was 10%,20%,30% and 50%,the turnround rate of MBC was separately 0.81 and 1.00a-1,0.79 and 0.81a-1,0.56 and 0.73a-1 as well as 0.31 and 0.42a-1; the turnaround time was separately 1.24 and 1.00a,1.27 and 1.23a,1.79 and 1.38a,3.27 and 2.37a.(4) The content of soil active organic carbon and stable organic carbon and management index of carbon stock had notable difference because of different intensity of intermediate cutting.In soil layer of 0-20cm, activity of carbon stock,the index of activity of carbon stock,index of carbon stock and management index of carbon stock had a general regularity for change among different forest zone under different intensity of intermediate cutting:F3>CK>F4>F1>F2.(5) When intensity of intermediate cutting was 30%,in soil layer of 0-10cm the ratio of carbon components of soil particle,the content of organic carbon and nitrogen of soil particle and the ratio of organic nitrogen were notably bigger than those of other forest zone. When intensity of intermediate cutting was 50%,the ratio of organic carbon and carbon components of soil particle were biggest in soil layer of 0-20cm.When intensity of intermediate cutting was 30%.the ratio took second place.The pattern of seasonal variation of POC was in accord with that of carbon components of soil particle.Within 20cm of forest chosen as contrast the seasonal variation of average content of POC was described autumn>winter>spring>summer. When intensity of intermediate cutting was 10%,20%,30% and 50%, the seasonal variation of average content of POC was described winter>autumn>spring>summer. |
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