Spatial Distribution And Mechanisms Of Soil Organic Carbon In Middle Of Heihe River, In Arid Area Of Northwest China

The thesis is designed to explore the spatial distribution and mechanisms of soil organic carbon (SOC) in Middle of Heihe River, in Arid area of Northwest China. The main conclusions are as follow:1. Soil profile SOC vertical distribution is gradually decreased with the depth increasing at the depth of 100cm, and content of non-active organic carbon (NOC) is more affected by the total soil organic carbon (TOC) than that of the active organic carbon (AOC). Spatial variation and distribution of SOC, AOC and NOC show the disciplinary trend. Finally, we obtain that the cultivated region is not only the high and centralized section of SOC content, but also the labile section.2. There is significant relationship between SOC and soil bulk density, PH value, different soil particle size content. The results show that the content of 10-50μm,50-250μm,250-1000μm particle size are affected after the others' soil types were changed to the cultivated plots. According to the result, we find the content of different soil particle size and SOC is significant variety by peoples' foster.3. Property cultivated measures may increase SOC content. SOC content is increasing in soil profile with the time of cultivation. The contribution of SOC content under the different crop is as follow from high to low in turn: cole plot (the cultivate chestnut soil), legume plot, general corn plot, corn plot of making seed, wheat (cotteon, barley) plot. Returning of organic manures and crop stubble enhance the content of SOC. The changing land-use from other's types to the cultivated plots makes the SOC content increase.4. TOC, AOC and NOC pool is 94.719Tg, 45.118Tg, 49.601Tg in the depth of 100cm in thestudy area, respectively. TOC contains 47.63% AOC and 52.36% NOC. According to the analysis, we find the changing land-use obviously alter the density and pool of soil organic carbon. The landscape of the dry land, paddy field, Urban land-use, the middle density grassland, the saline-alkali field, the nakeeness land, the desert, the sandlot extensively distribute the Middle of Heihe River, the otherness of the organic carbon density including TOC, AOC and NOC is great among them. So the translation among the above landscape directly impact and drive the changing of TOC, AOC and NOC. Finally, we estimate the increment of SOC pool for the cultivated role, the result show that the storage of TOC, AOC and NOC is increased 19.998 Tg, 8.334Tg and 11.78Tg, respectively.