The Study On Soil Labile Organic Carbon In The Upper Reaches Of Minjiang River

In this paper, it makes use of field investigation method, analysis of variance (ANOVA), correlation analysis and regression model to research content and distribution characteristics of Water-soluble organic carbon (WSOC), Dissolved organic carbon (DOC) and Readily organic carbon (ROC) in the upper reaches of Minjiang River. it analyzes the general physical and chemical properties of soil and its external impact factors with their re-lationships. The main research results are as follows:In the upper reaches of Minjiang River, The contents of WSOC are126.66±62.54and78.68±35.64mg kg-1at20-40and20-40cm respectively. The contents of DOC are67.22±34.46and44.60±20.97mg kg-1at20-40and20-40cm respectively. The contents of ROC are1.75±0.96and1.07±0.64g kg-1at20-40and20-40cm respectively.The contemts WSOC, DOC and ROC of cinnamon soil, brown earth, dark brown fore-st soil and subalpine meadow soil all present the law of dark brown forest soil>subalpine meadow soil>brown earth>cinnamon soil. Their differences all reach significant levels.Soil labile organic carbon (SLOC) has close reationship with soil property. WSOC, D-OC and ROC presents obivous negative correlation with pH,sand,clay and TK, while they present obvious positive correlation with silt, TOC, TN, TP, CEC.The content and change of WSOC are largely affected by soil parent material. WSOC and DOC are phyllite and limestone saprolite<river alluvium<meta-sandstone and slate slo-pe sediments, while ROC is river alluvium<phyllite and limestone saprolite<meta-sandsto-ne and slate slope sediments.Altitude leads to an obvious influence on SLOC. Take the altitude gradient of below1600,1600-2600,2600-3600and more than3600m, the difference of WSOC, DOC and R-OC all reach a significant level. Regression analysis indicates that the content of WSOC, DOC and ROC increase with elevations rise.Slope has an obvious influence on SLOC. Under different slope, the difference of the content of WSOC and ROC reach a significant level, while the differenecof the content of DOC don’t reach a significant level. On the whole, the content decreases with the rise of sl-ope, but from10to45degree, it presents no obvious changes. Aspect has an obvious influence on SLOC. The contents of WSOC, DOC and ROC of different aspect exist obvious difference. For WSOC, shoutheast and west aspect is higher while partial eastern aspect is lower. For DOC and ROC, partial northern aspect is higher, partial eastern and southern aspect is lower.Vegetation types has an significant influence on SLOC. At the evergreen broad-leaf fo-rest, needle broadly mixed forest, shrubbery and grassland these4types of vegetation type-s, the content of WSOC, DOC and ROC all present obvious difference. They all present th-at the content of needle broadly mixed forest is the highest192.64,82.63and2.21g kg-1respectively, and shrubbery’s the lowest86.41,40.02and1.13g kg-1respectively.Land Use Type has an significant influence on SLOC. The content of WSOC, DOC and ROC presents obvious difference at broad-leaved forest land, coniferous forest land, sparse woodlands, shrubland and grassland. They all present that the content of coniferous forest land is the highest176.09,85.54mg kg-1and2.23g kg-1respectively, and sparse woodlands the lowest78.90,48.62mg kg-1and1.01g kg-1respectively.The distance has an obvious influence on SLOC. The relatunship of WSOC, DOC and ROC with distance is less than1.5<1.5-5<5-15<more than15km, which means that the content increases with the rise of distance. Variance analysis indicates that under different distance range, the content of WSOC has significant differences, while the contents of DOC and ROC pressent no great didderence.