Spatial Distribution Ferture Of Soil Organic Carbon And Its Influences Factors Of A Small Watershed In Gully Region Of Loess Plateau

Soil organic carbon( SOC) is a large component of the global carbon cycle and an important index to evaluate soil quality. Soil productivity is strongly linked to SOC because SOC plays important roles in improving soil structure, soil water holding, infiltrating and capacities, and the nutrients supply to plants. It is significant that effect of land-use, vegetations types and landform on soil organic carbon turnover , distribution and storage in gully area of the Loess Plateau. In this thesis, 448 observed points of surface (0²0cm) and 29 observed profile (0²00) were made in Wangdonggou watershed in gully region of Loess Plateau. Spatial variability of SOC content was analyzed by geostatistics approach. The complex factors affected spatial variability of soil carbon content was preliminarily discussed. The storage of SOC C pool was estimated in the whole watershed. The main results were as follows:Soil content of Wangdonggou watershed was in the range of 3.59-15.97 g·kg^-1, the average were 7.58g·kg^-1. The variability coefficients of SOC were 26.9%,it's belong to middle intensity .SOC content on table land, on slope land and in valley were in the range of 6.41-9.50 g·kg^-1, 2.71-15.97 ·kg^-1 and 3.59-15.18 g·kg^-1 respectively. The variability coefficients of SOC on table land was 7.5%, belong to low intensity, on slope land and in valley were 25.7 %and 26.7%respectively and belonged to the middle intensity.SOC concentrations under different land use patterns have significant differences in table land, soc concentration of cropland , orchard and clover were in the range of 6.41⁹.50g·kg^-1, 6.25-8.54 g·kg^-1 and 8.28-9.10 g·kg^-1 respectively. Compared with cropland, SOC content increased by 7.1% for clover and decreased by 5.3%⁹.1% for orchard on tableland. The content of soc could be put in orders as: forestland > grassland > clover > cropland > orchard. The average content of soc in cropland was 6.38 g·kg^-1, it was decreased by 5.5% after converting from crop land to orchard and soc content was increased by 16.6-47.4% after converting from crop land to forestland or grassland. Soc content was increased with the increased of the year of forest. Soc content of forest and grassland were 3.59-15.18 g·kg^-1and 5.08-13.78 g·kg^-1 respectively in valley. The distribution of the SOC concentration or inventory in soil profile would change with the change of land use in wangdonggou watershed.Compared with grass (Bothriochloaischaemum(L.)Keng)land, SOC content...