Study On The Evolution Characteristics And Influence Mechanism Of Soil Carbon Pool Under The Restoration Of Vegetation In Ziwuling

Vegetation restoration and reconstruction is an effective important measure that could control soil and water loss and improve ecological environment, the dynamic characteristic of soil carbon pool is the important basis to measure regional ecological effect. Under the background in the returning farmland to forest (grass), this paper adopt the method that combining the space time, field investigation and indoor experiment, the typical sample area of vegetation restoration in loess plateau for sampling and determination could be analyze, discussed the dynamic characteristic of soil organic carbon, soil high fraction organic carbon and soil microbial biomass carbon in the process of vegetation restoration and reconstruction, analyzing the correlation relationship between soil physicochemical property and oil carbon pool, illustrating the direct and indirect factors that affects soil organic carbon, soil high fraction organic carbon and soil microbial biomass carbon change. Aim to a comprehensive restoration in loess plateau, giving guidance on loess plateau vegetation restoration and provide a scientific reference for reconstruction work. The main conclusions are as follows:1.The effect of vegetation restoration on soil bulk density, pH, conductivity, total nitrogen is greater, the effect of vegetation restoration on soil water content is middle, the effect of vegetation restoration on the watet-stable aggregation, soil particle and total phosphorus is little. And the effect of vegetation restoration on soil water content and total nitrogen is positively, the effect of vegetation restoration on soil bulk density, pH and conductivity is negatively.2. With the increasing of the grassland restoration ages, the soil organic carbon increases In different vegetation restoration types, soil organic carbon content as follows: farmland< grassland< shrubland< Mixed-forest< Aspen< quercus, in 0-10cm.The content of SOC surface is more greater than the lower in both all grassland restoration ages and vegetation types. The enrichment effects of SOC in the soil surface was obvious.3. Soil high fraction organic carbon was steadily increases with the increasing of the grassland restoration ages before 27a, there was a greatly increase in 35a, in 0-10cm soil layers. The variation tendency of soil high fraction organic carbon with the increasing of grassland restoration ages is fall "W". There is big difference of soil high fraction organic carbon all vegetation restoration types. The content of SHFC in 0-10cm as follows:farmland< shrubland< grassland< Mixed-forest< Aspen< quercus, there were significantly different between Mixed-forest, Aspen, quercus and farmland, there were no significantly different betweenshrubland, grassland and farmland. The content of SHFC in 10-20cm as follows:shrubland< farmland< Mixed-forest< grassland< quercus< Aspen, only were there significantly different between Aspen and others. The content of SHFC surface is more than the lower in both all grassland restoration ages and vegetation types. The enrichment effects of SHFC in the soil surface was obvious.4. With the increasing of the grassland restoration ages, the soil microbial biomass carbon increases, the maximum content of SMBC is Mixed-forest in all vegetation restoration types. Compared with farmland, the effect of vegetation restoration to improve the soil fertility and quality is significant, and the soil fertility and quality is better and better with the grassland restoration ages increasing, the Mixed-forest is the best measure to improve the soil fertility and quality in all vegetation restoration types. The content of SMBC surface is more than the lower in both all grassland restoration ages and vegetation types. The enrichment effects of SMBC in the soil surface was obvious.5. Through the path analysis of SOC, SHFC and SMBC, this research showed that the main impact factors of SOC were soil total nitrogen, bulk density, total phosphorus and electric conductivity. And the total nitrogen was the direct factor, however the total was the indirect factor. The direct impact factors of SHFC was total nitrogen, soil water content and total phosphorus. The direct impact factors of SMBC was total nitrogen and water content. In the process of vegetation restoration, through the path analysis the impact factor and influence mechanism of SOC, SHFC and SMBC, the research also showed that decision coefficient of surplus factor is big, it means that there are still some important factors have not been taken into consideration, (such land use types, micro-topography, etc), need to strengthen the study of soil carbon pool, response mechanism.