Concentration And Distribution Characteristics Of Soil Labile Organic Carbon In Yalong River Valley

Soil organic carbon is an important issue in the study of global climate change.In order to research the concentration and distribution characteristics of three soil labile organic carbon-dissolved organic carbon (DOC), water-soluble organic carbon (WSOC) and readily organic carbon (ROC) in the Yalong River Valley, the0-20cm surface soil sampling were studied by field investigation, analysis of variance and regression correlation analysis. This paper mainly analysised the relationship between the three kinds of labile organic carbon and soil general physical and chemical properties such as soil pH, particle composition, T, P, and K. and studied the affecting of altitude, vegetation, land use and other factors on soil labile organic carbon. Major findings were as follows:The soil DOC concentration was51.64±3.24mg kg-1, accounted for0.20%of TOC; the concentration of WSOC was23.10±14.08mg kg-1, the average proportion of TOC was0.40%; the concentration of ROC was3.92±2.77mg kg-1, accounted for0.01%of TOC. All the concentrations of DOC, WSOC, ROC were normal distribution (K-S test P>0.05), they showed a significant positive correlation (P<0.01) with TOC.Soil labile organic carbon concentration was significantly different in different soil types. DOC concentrations and soil type showed a very significant correlation (P<0.01), the DOC’s concentrations of meadow soil was very significant higher than dark brown soil, alpine meadow soil was very significant higher than brown soil, brown soil was significantly higher than dark brown soil. Soil type and concentrations of WSOC were significant correlation (P<0.05), the WSOC’s concentrations of meadow soil were significantly higher than dark brown soil and brown soil, alpine meadow soil was significantly higher than dark brown soil and brown soil. ROC concentrations and soil type showed a significant correlation (P<0.05), alpine meadow soil was significantly higher than brown soil, subalpine meadow soil was significantly higher than that of brown soil and dark brown soil.DOC, WSOC, ROC concentrations had a significant correlation with the soil physical and chemical properties. There was a significant negative correlation between soil labile carbon and pH; it showed a highly significant negative correlation with sand and clay, showed a significant positive correlation with silt; DOC, WSOC and ROC concentrations were increased with the increase of TN and TP concentration, showed a trend to decrease with the increase of TK concentration.Altitude had significant effects on soil labile organic carbon. The concentrations of DOC,WSOC,ROC and altitude were extremely significant correlation (P<0.01); the difference of DOC, WSOC and ROC’s concentrations under the four elevation gradient (elevation under1600m,1600-2600m,2600-3600m and3600m above) reached very significant level; Altitude>4000m area was significantly higher than the other three altitudinal gradient range of labile organic carbon concentration (P<0.01), the overall trend was that with the increase of altitude, the labile organic carbon concentration showed a trend of increasing.Vegetation types and the labile organic carbon were significant or very significant correlation. Studied the five types of vegetation--coniferous and broad-leaved mixed forest, coniferous forest, shrub forest, grassland, alpine meadow of the Yalong River Valley shows that effect of vegetation type on DOC concentration was significant(P<0.05),and very significant effects on WSOC, ROC (P<0.01). DOC concentration was highest in the shrub, the lowest was coniferous forest; alpine meadow WSOC concentration was the highest, coniferous forest was the lowest; ROC concentration in alpine meadow was the highest, the lowest was coniferous forest.Labile organic carbon concentration under different land use types was significantly difference. The effect of land use types on DOC, WSOC and ROC concentration was very significantly (P<0.01);Studies the five way of land use types-grassland, meadows, scrub meadows, thickets of woodland and forest land in the Yalong River Valley indicated that: the highest DOC concentration was scrub meadows, minimum was thickets of woodland; WSOC’s highest concentration was forest land, thickets of woodland had the lowest concentration; forest land’s ROC concentration was highest, thickets of woodland was lowest.