Abstract
Changing characteristics of soil organic carbon and active organic carbon concentrations were studied along an altitudinal gradient of natural spruce forest of Mount Tianshan, Xinjiang, China. Soil samples were collected from different soil depths from three different elevations i.e., 1800-2000, 2200-2400 and 2600-2800 m, respectively. The characteristics of soil organic carbon mineralization, as well as other factors affecting the process, were evaluated using double exponential equations. The results showed that soil organic carbon and active carbon concentrations had an obvious surface enrichment phenomenon. There were no significant differences in total soil organic carbon between different elevations. Surface soil active carbon concentrations significantly decreased at elevations of 2600-2800 m due to less litter and lower temperature. The results indicated a similar mineralization process with strong reaction intensity at early stages followed by a gradual reduction in intensity in 0-100 cm depth of soil at the three elevations. Organic carbon mineralization intensity is affected by soil active carbon concentration and temperature and decreased significantly between 0-40 cm at the high elevation of 2600-2800 m. Compared with total soil organic carbon, the soil active carbon concentration affected the mineralization process and intensity more directly.
Highlights
Soil organic carbon mineralization refers to the decomposition of the organic carbon in soil by microbes into CO2
Characteristics of vertical distribution of soil organic carbon content: A vertical analysis of the cross-section of the soil at different elevation gradients revealed that the organic carbon content in the soil decreased as the soil depth increased (Table 2)
A highest contrentation of soil organic carbon was observed at a depth of 0-20 cm at both 1800-2000 and 2200-2400 m of elevation, with a range of 95.93-78.58 g/kg, showing a striking difference from the lower soil condition
Summary
Soil organic carbon mineralization refers to the decomposition of the organic carbon in soil by microbes into CO2. Collins et al (1992) analyzed the reaction properties of the mineralization process based on the composition of the soil organic carbon. Davidson et al (2000) and Hopkins et al (2006) studied the role of soil organic carbon content on the mineralization intensity. These related studies have introduced various types of equations, such as exponential, double exponential, exponential-plus-liner, exponential-plus-constant and hyperbolic equations, into analyses of the soil organic carbon mineralization process. Considering the complexity of the composition of soil organic carbon, Parton et al (1989) subdivided soil organic carbon into 3 types according to the stability and turnaround time of the various components: activated carbon, slow carbon and resistant carbon
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