The Vertical Distribution And Environmental Factors Of Soil Organic Carbon In Daweishan National Forest Park

Forest ecosystems play an irreplaceable role in the global carbon cycle and carbon balance. As an important part of forest ecosystems, forest soils play a role as sources, sinks, library in the global carbon cycle. Forest soil carbon storage and spatial distribution have become a hot issue of global organic carbon cycle research. This paper studied four kinds of soil cross-sections under different vegetation communities in Daweishan National Forest Park, including evergreen broad-leaved forest, artificial forest, deciduous forest, grass and shrub communities. Vegetation community composition was investigated. Then cutting ring samples and soil samples were collected and soil basic physical arid chemical properties were measured. Moreover, the vertical distribution of soil organic carbon was explored and its influencing factors of soil organic carbon content and soil organic carbon density were analyzed. The results showed that:1. The basic physical and chemical properties of soils in Daweishan National Forest Park presented significant levels of vertical distribution in each cross-section. With increasing of depth in each cross-section, the content of moisture in soil was decreased, and the lowest one reached15.86%. The moisture content of topsoil (0-20cm) was higher than others, which were between20.08%and40.28%. Soil capillary porosity showed a decreasing trend, the lowest reached37.60%. With the increasing of soil depth, soil bulk density was gradually increased up to1.63g·cm-3,the pH ranged from4.43to4.95with strong acidic and total N concentration decreased gradually, but the soil total P was opposite.2. Content of organic carbon in typical forest soils in Daweishan National Forest Park presented a clear hierarchy. With the increasing of soil depth in the section vertical distribution, content of the organic carbon decreased gradually and stabilized when the depth was under60cm. Soil organic carbon content and humus components presented a strong correlation, especially humic acid. Average content of humic acid and fulvic acid content in each cross-section was0.83g·kg-1and3.46g·kg-1, respectively. Overall the humic acid content was less than fulvic acid in the soil, which indicated that humic acids fulvic acid was the main ingredient of humus components.3. Correlation analysis showed that, there was a significant positive correlation between soil moisture and organic carbon content. But soil bulk density and organic carbon data were found a significant negative correlation (y=-38.174x+60.92, R2=0.6148). The correlation between soil capillary porosity and soil organic carbon content was not obvious. Total N and soil organic carbon content showed a significant positive correlation (y=15.11x-3.5804, R2=0.9285). So as the total P, but was weaker.4. The calculated by measuring the organic carbon density showed that, vertical distribution (0-100cm) of organic carbon density in different soil types were between11.25to19.22kgm-2, with an average of14.70kgm-2. Throughout the whole study area, soil organic carbon density from higer to low were:place D (grass and shrub communities, shrub meadow soil,1465m)> place B (deciduous forests, yellow brown soil,1402m)> place C (deciduous forests, yellow soil,1002m)> place A (artificial forest, red-yellow soil,800m). In conclusion, the altitude was the main factor affecting soil organic carbon density.