Correlations Between Soil Organic Carbon Fractions With Variable Links To Soil Physical Properties In An Alpine Pastureland

Generally believing, increasing the content of soil organic matter can effectively improve the soil physical properties. However, correlations between soil organic carbon fractions themselves and theirs with variable links to soil physical properties in an alpine pastureland have not be well understood. Aim of this study was to investigate relationships of soil organic carbon fractions and their soil physical properties (in the depth of 30cm, six pastureland and 51 soil samples) and therefore further we may know their value of economy. The main conclusion as follows:1. Significant positive linear relationships were found between microbial biomass carbon, coarse organic carbon, stable organic carbon, water-soluble organic carbon, humus organic carbon, carbohydrate carbon and total organic carbon. Meanwhile, linear relationships between humus organic carbon and the total organic carbon(r=0.91, p<0.001) were most significant which indicated that the contents of total organic carbon are based on the humus organic carbon. The coarse organic carbon and stable organic carbon was positive linear relationships to the humus organic carbon. A positive and high relationship was found between carbohydrate carbon contents and coarse organic carbon, microbial biomass carbon and Mineralized C which showed important relation of carbohydrate carbon contents and microbial biomass, carbohydrate carbon mainly being among coarse organic carbon and easy mineralized. Microbial biomass carbon and mineralized C was associated with coarse organic carbon, humus organic carbon, water-soluble organic carbon and carbohydrate carbon. The Mineralized C presented the highest correlation with coarse organic carbon(r=0.93, p<0.001), showing Mineralized C coming mainly from coarse organic carbon fraction, the coarse organic carbon is a mainly basic of soil microbial breath.2. Correlation between fractions soil physical properties( in water stability of >0.25mm aggregates MWD(mean weight diameter), particle density, bulk density, porosity , water holding capacity of soils) and grassland soil organic carbon were also evaluated relative to soil physical degradation. There a passive and high relationship between bulk density and particle density(p<0.001) and soil total organic carbon, whereas between water stable aggregate MWD , porosity , water holding capacity and soil total organic carbon presented positive and high correlation(p<0.001), showing it was important that effects of soil organic carbon on soil physical properties. Water stable aggregate MWD presented high correlation with humus organic carbon, stable organic carbon, concentrated-acid extracted carbohydrate-C, diluted-acid extracted carbohydrate-C and low correlation and coarse organic carbon, microbial biomass carbon, mineralized C, Hot-water extracted Carbohydrate-C. This result showed that some of all organic carbon influence on water stable aggregate.3. The research shows in alpine region that soil water stability of aggregate MWD was mainly affected by humus organic carbon, stable organic carbon, concentrated-acid extracted carbohydrate-C and diluted-acid extracted carbohydrate-C, and correlation coefficient(r) is stable organic carbon(r=0.62)>diluted-acid extracted carbohydrate-C(r=0.49) > humus organic carbon(r=0.47) >concentrated-acid extracted carbohydrate-C(r=0.46). Our results indicated that soil system in alpine region was very frangible, soil managements in present study reduced soil organic pool, which lowed soil stability of aggregate and accelerated loss of soil with water, therefore threaten ecological function of soil.