| Soil labile organic carbon(LOC) refers to the fractions of organic carbons that are easy to move and to be oxidized and mineralized, Soil labile organic carbon is subject to plants, microorganisms strong in certain conditions of time and space, with a certain solubility, and easy to move and to be oxidized, easy to decompose and mineralization in the soils, and they are quite available to plant and soil microorganisms, conversion of biochemical processes involved in soil fast and direct.although only a small part of the soil total carbon, but can be sensitive to reflect the different production practices on soil carbon storage and potential productivity Indicate early changes of soil organic matter. Soil labile organic carbon as an important component of the soil, the index has been used to evaluate the effect of restoration of degraded ecosystems, its content and dynamic changes can reflect the size of soil available nutrient pool and turnover in the soil.The initial planting density and canopy of spruce (Picea asperata) plantation in subalpine of western Sichuan is too large, So there were only a small number of herbaceous and almost no shrubs understory. The spruce plantation ecological functions are in a degraded condition, and its production functions are very low.Structure of control as the main measure of forest management is the impact on biodiversity within forest ecosystems important factor, which for the trees to create a good growing environment, improve the forest soil, affecting the ecological functions of forests. This study researched Seasonal dynamics of Soil labile organic carbon in spruce plantation of artificial promotion regeneration forest gaps of different size (50 m2,100 m2,150 m2), natural regeneration gaps of different sizes (50 m2,100 m2,150 m2), diferent thinning intensity (10%,20%,30%,50%) and control comparison (CK) in Miyaluo forest area of subalpine of western Sichuan by using the dynamic combination of sampling and analysis methods. The results were mainly as follows:(1)Regulation of spruce plantations of different structures, the upper and lower soil total organic carbon (TOC) and particulate organic carbon (POC) content consistent seasonal variation, Showed an increased gradually from spring to summer, rise to the highest values in summer, from summer to autumn, the carbon content began to fall, in winter there is some increased, the performance variation of N-shaped. Dissolved organic carbon (DOC) in soil trend of seasonal variation:highest in spring, lowest in summer, from spring the content gradually reduced to a minimum during the summer and then rising, was "V" shape.And soil microbial biomass carbon (SMBC) and readily oxidizable carbon (ROC) content of the seasonal trends are basically the same, as follows:fall> winter> spring> summer.(2)Under the artificial promotion regeneration forest gaps of different size in spruce plantation, throughout the entire growing season, the mean upper and lower soil TOC is 100 m2 gap>150 m2 gap>50 m2 gap>control comparison, The TOC content of annual average is 25.76g·kg-1 in 100 m2 gap, is 1.37 times the control comparison; Dissolved organic carbon (DOC) content of mean upper and lower is 100 m2 gap>150 m2 gap>50 m2 gap>control comparison,the DOC content in 100 m2 gap is 70.03 mg·kg-1,1.32 times the control; Soil microbial biomass carbon (SMBC) content of the mean upper and lower is 100 m2 gap>150 m2 gap>50 m2 gap>control comparison, the SMBC of the annual average in 100 m2 gap is 546.77 mg·kg-1, is 1.23 times the control comparison;Readily oxidizable carbon (ROC) content of the mean upper and lower is 150 m2 gap>100 m2 gap>50 m2 gap> control comparison, the ROC of the annual average in 150 m2 gap is 5.13g·kg-1, is 1.67 times the control comparison;Particulate organic carbon (POC) content of the mean upper and lower is 100 m2 gap>150 m2 gap> 50 m2 gap>control comparison, the POC of the annual average in 100 m2 gap is 7.82 g·kg-1, is 1.83 times the 50 m2 gap;Combination of all active organic carbon content, optimal treatment of artificial promotion regeneration forest gaps of different size in spruce plantation may be 100 m2 gap.(3) Under the natural regeneration gaps of different sizes in spruce plantation, throughout the entire growing season, the mean upper and lower soil TOC is 50 m2 gap>100 m2 gap>150 m2 gap>control comparison, The TOC content of annual average is 54.85 g·kg-1 in 50 m2 gap, is 1.46 times the control comparison; Dissolved organic carbon(DOC)content of mean upper and lower is 50 m2 gap>100 m2 gap>150 m2 gap>control comparison,the DOC content in 50 m2 gap is 80.42 mg·kg-1,1.52 times the control; Soil microbial biomass carbon (SMBC) content of the mean upper and lower is 50 m2 gap>100 m2 gap>control comparison>150 m2 gap, the SMBC of the annual average in 50 m2 gap is 538.71 mg'kg-1, is 1.60 times the 150 m2 gap; Readily oxidizable carbon(ROC)content of the mean upper and lower is 50 m2 gap>100 m2 gap>150 m2 gap>control comparison, the ROC of the annual average in 50 m2 gap is 5.74g·kg-1, is 1.87 times the control comparison;Particulate organic carbon (POC) content of the mean upper and lower is 50 m2 gap>100 m2 gap>control comparison>150 m2 gap, the POC of the annual average in 50 m2 gap is 10.65 g'kg"1, is 2.52 times the 150 m2 gap; Combination of all active organic carbon content, optimal treatment of artificial promotion regeneration forest gaps of different size in spruce plantation may be 50 m2 gap.(4) Under the diferent thinning intensity in spruce plantation, throughout the entire growing season, the mean upper and lower soil TOC is 30%thinning intensity> 20% thinning intensity> 10% thinning intensity> 50% thinning intensity>control comparison, The TOC content of annual average is 28.82 g'kg"1 in 30% thinning intensity, is 1.54 times the control comparison; Dissolved organic carbon (DOC) content of mean upper and lower is 30% thinning intensity> 20% thinning intensity> 10% thinning intensity> 50% thinning intensity>control comparison, the DOC content in 30%thinning intensity is 75.87 mg'kg"1, 1.543 times the control comparison; Soil microbial biomass carbon (SMBC) content of the mean upper and lower is 30% thinning intensity> 20% thinning intensity> 10% thinning intensity> control comparison> 50% thinning intensity, the SMBC of the annual average in 30% thinning intensity is 544.41 mg·kg-1, is 1.21 times the 50% thinning intensity; Readily oxidizable carbon (ROC) content of the mean upper and lower is 30% thinning intensity> 20% thinning intensity> 50% thinning intensity>10% thinning intensity> control compa-rison, the ROC of the annual average in 30% thinning intensity is 9.36g·kg-1, is 1.53 times the control comparison; Particulate organic carbon (POC) content of the mean upper and lower is 30% thinning intensity> 20% thinning intensity> 50% thinning intensity> control comparison> 10% thinning intensity, the POC of the annual average in 30% thinning intensity is 16.23 g·kg-1, is 1.75 times the 10% thinning intensity; Combination of all active organic carbon content, optimal treatment of diferent thinning intensity in spruce plantation may be 30% thining intensity. After the Pearson correlation analysis among the soil organic carbon content quantity and various activated carbons as well as each kind of activated carbon, finally the result indicated that there is a strong relevance among the soil organic carbon content and four active organic carbon. At the same time, there is a strong relevance among the DOC, SMBC, ROC, POC. Among a variety of soil active organic carbon and soil enzyme activities has a significant negative correlation; and between a variety of soil active organic carbon and the soil temperature has a significant negative correlation; DOC, SMBC, ROC, POC and pH values has a significant negative correlation. |
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