Soil Organic Carbon Components and Their Correlation with Soil Physicochemical Factors in Four Different Land Use Types of the Northern Tarim Basin

Abstract

In order to clarify the distribution of each component of soil organic carbon (SOC) in arid areas, and to develop methods to rationally solve problems caused by inefficient land use and blind tillage, we studied the effects of different land use patterns on the SOC, microbial biomass carbon (MBC), dissolved organic carbon carbon (DOC), and easily oxidized organic carbon (EOC) on four different land use types: saline soil, natural forest, sandy land, and 30 a cotton field in the northern Tarim Basin. The relationships between different carbon components and soil physicochemical factors were researched by redundancy analysis (RDA). The results showed that the SOC showed the highest value (1.92 g·kg-1) in natural forests and increased with soil depth, while the other land use types showed a downward trend as a whole. The MBC showed the highest level in natural forests, and decreased with soil depth, but there was no obvious change trends in other land use types. The highest and lowest DOC contents appeared in the 80-100 cm layer (143.23 mg·kg-1 and 30.00 mg·kg-1, respectively) in the natural forest and 30 a cotton field, respectively, and increased with soil depth in the natural forest (P<0.05). In the saline soil, the DOC content of the soil decreased with increased depth, and the contents of different soil layers showed significant differences (P<0.05). The EOC content did not show a obvious regularity in different soil layers of different land use types. Sensitivity analysis of each organic carbon component showed that the MBC was the most sensitive to soil layer changes, and the DOC was the most sensitive to different land use patterns. The MBC has a certain indication of soil layer change, which may be due to the fact that microbial biomass C in different layers has different living environments, so the content was significantly different. The DOC has a certain indication of land use types change, which may be due to the adaptation to different situations. Through the RDA, it was found that there was a positive correlation between soil components and soil water content (SWC), total nitrogen (TN) and pH, and a negative relationship between bulk density (BD) and electrical conductivity (EC). The order of importance of environmental factors to the contents of carbon components is as follows: BD > SWC > EC > TN > pH. This indicates that bulk density and water content are the main factors affecting organic carbon components in arid regions.