The Study Of Soil Carbon Storage Under Different Poplar-crop Intercropping Patterns

Soil organic carbon (SOC) content and its dynamic balance, an important indicator of a direct impact on the level of soil fertility and crop yield, reflect soil quality or soil health. In this paper, soil organic carbon, microbial biomass carbon, dissolved organic carbon, soil mineralizable organic carbon were investigated in three poplar-crop agroforestry systems in order to provide an effective carbon sink data of soil carbon storage, carbon emission, spatial variability and the annual changes. The major findings are as follows:1. Soil organic carbon content decreased with increasing of soil depth in all three management patterns (K, P, W). The organic carbon concentrations in surface soil (0-20cm) had relatively high, then organic carbon content decreased rapidly as the soil depth increasing. Variance analysis showed that soil organic carbon content was significantly different among the three patterns (P <0.01).2. Microbial biomass C also decreased with soil depth increaseing, similar distribution to soil organic carbon. Analysis of variance showed that microbial biomass C content in K pattern and W pattern was significantly different between the depth of 0 ~ 20cm and the other layers(P <0.01), while no significant difference was observed between the other layers (P> 0.05).3. A significant seasonal variation in microbial biomass C was found in the three patterns, and value appeared low in winter and spring, whereas values in summer and autumn reached high. Analysis of variance showed that growth season had significant effects on microbial biomass C in the three patterns (P <0.01). Microbial biomass carbon was significantly related to organic carbon content (P <0.01).4. Similar pattern in the vertical distribution of soil dissolved organic carbon was also observed. Soil dissolved organic carbon in different soil layers was significantly different for the three management patterns (P <0.05).Analysis of variance showed that seasonal changes in DOC for soil profiles of three patterns were very significant (P <0.01), suggesting that the variation of soil DOC content was greatly influenced by management pattern and seasonal management practices (water, fertilizer, gas, heat).5. Mineralizable soil carbon content in the vertical distribution was different from the trend mentioned above, increasing as the soil layers deepening. Soil carbon mineralization showed an obvious seasonal variation, and trend was high in warm season and low in cold season. Analysis of variance showed that growing season had a significant effect on mineralizable carbon content of soil (P <0.01).