On The Spatial Distribution Patterns Of Soil Organic Carbon In The Northern Slope In The Middle Section Of Tianshan Mountainous

Soil carbon pool is the largest one stored in the earth surface system; and the stability and increase of soil organic carbon have been now well recognized internationally as one of the major means of slowing down the rise of CO2 density in the atmosphere. The northern slope of the Tianshan Mountains is the intersecting area of arid mountainous eco-system and desert eco-system, a sensitive area to natural changes. Being relatively less influenced by human activities, this area is an ideal place for soil organic carbon research, which will be of specially significance in predicting the tendency of regional environmental changesSupported by an open research program of Oasis Ecology Laboratory——Xinjiang Key Laboratory, this dissertation has made a comprehensive study of the spatial distribution features of soil organic carbon in the middle section of the northern slope of the Tianshan Mountains by integrating multi-disciplinary theories and techniques. Focusing on Urumqi River region, this study has chosen 119 typical profiles on the basis of a comprehensive survey of soil types and soil type distribution features. It has systematically collected soil samples and tested such indexes as soil organic carbon, oxygen-prone organic carbon, nitrogen, phosphorus, potassium, CaCO3 content, pH value, weight and soil composite; and also estimated the density and storage of soil organic carbon. This research aims to reveal the spatial differences of soil organic carbon.Such a systematic study yields certain conclusions as follows.1. The soil organic carbon in the vertical zone of the northern slope in the middle section of the Tianshan Mountains has an average profile content of 26.88 g/kg, of which the humus horizon has a content of 11.43 g/kg on average, amounting to 42.52% of the total profile content. The surface soil is the major distribution layer of soil organic carbon. This conclusion conforms to those done in similar zones at home, but with a higher percentage. Soil types have a greater spatial heterogeneity of organic carbon distribution. In areas at middle and plus elevation, soil organic carbon is relatively richer, which implicates comparably favorable thermo-hydraulic conditions2. The soil organic carbon shares a greater similar distribution with that soil organic carbon density. The study of the soil organic carbon density shows that the density of profile organic carbon is 46.91 C kg/m2 on average, of which the humus horizon has an average of 13.95 C kg/m2, taking up 29.74% of the total humus horizon. Soil types have a prominent impact on the density of soil organic carbon. 3. The calculation in this study indicates that the soils under research have 7452.98×104t of organic carbon, different soil types have greatly varying storages of organic carbon. 2335.75×104t being in the surface, taking up 31.34% of the total storage. Sub-alpine meadow soils have the largest storage, followed by mountain gray cinamon forest soils. These two take up 62.2% of the total storage in the area under research, making them the major area of organic carbon storage.4. The introduction of soil richness rate index serves to evaluate the potential of organic carbon storage in different soil types, which expresses the mechanism of soil organic carbon difference distribution in the vertical zone. The calculation in this study indicates that the Mountain chernozem soils are the greatest in their potential of storing organic carbon, the soil profile richness rate index is 20.91, and it's humus horizon richness rate index is 24.50.5. Soils are of diverse types in the area under research, which are the results of environmental changes. Soil fertilization potentials are closely related to soil types and vertical zones, mountain gray cinnamon forest soil and mountain chernozem soils being the highest, followed by subalpine and alpine meadow soils and then by mountain chestnut soils mountain brown calcic soils).6. Being relative relief (790-4200m) is big in difference vertically, and the area under research has an obvious impact in the mountain area, this dissertation introduces the term, continental rate, for the first time, to study the impact of climatic factors on soil organic carbon distribution, which is theoretically significant in studying the mechanism of soil organic carbon storage in mountainous areas.