| Soil carbon is an important part of terrestrial ecosystem carbon cycle. In this thesis, 62 observed points were made in Zhuanyaogou watershed in hills region of Loess Plateau. Spatial variability of soil inorganic carbonate carbon (SIC) content and of soil organic carbon(SOC) content were analyzed by geostatistics approach. The complex factors affected spatial variability of soil carbon content were preliminarily discussed The storages of SIC and SOC C pool were estimated in the whole watershed Based on the two years located research, the storage of CO2 C pool in same watershed was estimated too. The main results were as follows.Among the 10 soil layers in the range of 0-200cm depth, except one or two layers in which those obeyed the logistic normal distribution, the contents of SIC and SOC in the others obeyed the normal distribution. The mean content values of SIC and of SOC in different layer were in the range of 10.78-12.16g/kg and of 1.46-4.13g/kg respectively. The soils at the layer of 60-80cm depth had the maximum content of SIC and the maximum SOC content was in the surface soils. This distribution pattern of soil carbon was related to such factors as the precipitation eluviation and the organism activities in soils. The variability coefficients of SIC and of SOC at different soil layer were in the range of 0.10-0.14 and of 0.26-0.36 respectively and belonged to the middle intensity Obviously, the variability coefficients of SOC exceeded those of SIC. The possible reason was that they stemmed from different substance.As regionalized variables, the contents of SIC and of SOC had the characteristic of structure as well as random. Spatial structure analysis indicated that the semivanograms of SIC and of SOC content at different soil layer were simulated by different theoretical models and had same obvious spatial structure. Their correlated distances were 1 km or so. The SIC content at the layer of 20-40cm had the smallest correlated distance of 0.9474km and the SOC content at the layer of 10-20cm had the biggest correlated distance of 1.4113km. The spatial variability at all of soil layers was contributed to the influencing of the correlation rather than of the random.At the same soil layer, the SIC contents on the tops of the hills were higher than those in the gullies, however, the SOC contents on the tops of the hills were lower than those in the valleys. The possible factors of influence on the distribution of soil carbonwere soil water content and human activities. As far as soil profile carbon contents were concerned, on the tops of the hills the profile SIC content had the maximum change and the profile SOC content had the minimum change. On the contrary, the valley soils had the minimum change for the profile SIC content and the maximum change for the profile SOC content The diversity of the soil profile carbon content change were related to their sources, movements and inversions in the soils.The results of the rough estimation showed that the total reserves of SIC , SOC and CO2 C pool were about 88.64 104t, 13.11 104t and 3.739t~81.937t respectively in the range of 0-200cm depth in Zhuanyaogou watershed. The storages of SIC, SOC and CO2 C pool in the range of 0-100cm depth were 50.76 %, 58.97 % and 50 % of the total reserve of SIC, SOC and CO2 C pool in the range of 0-200cm depth of the same watershed respectively. The results indicated mat the soil carbon storage in the depth of 100-200cm was important for predicting the total soil carbon reserve in the whole watershed.In Zhuanyaogou watershed, mere was approximately 5-6 times as much carbon stored in inorganic form as in organic form in soils. The major C pool of the loess was SIC, the next was SOC. The gaseous CO2 was only a small portion. The study about carbon stored in inorganic form .especially carbonate carbon, should be highly valued in the loess plateau.The storage of SOC in Zhuanyaogou watershed was lower than the mean value of SOC reserve in the loess plateau. The low content of soil organic matter was the limiti...
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