| Global warming is becoming one of the major environmental problems in present. Study found that there is direct relationship between global pattern of carbon cycle and global warming. Under the background of global warming, the global carbon cycle research was born to be a science hot spot. Effects of soil erosion on soil carbon pool are directly related to the global carbon circulation pattern. However, soil erosion actually means "carbon source " or "carbon sink" in the soil carbon cycle pattern was unknown and there were widespread controversy among scientific community. A key uncertainty is microbial response characteristics induced by erosion and its implication on global carbon cycle, making it impossible to accurately estimate the specific role of erosion acting soil carbon pool. A field simulated rainfall experiment was conducted on a runoff plot (2m x 5m), to study the changes of SOC, total nitrogen (TN), total phosphorus (TP), soil mechanical composition and soil moisture content under soil erosion, and dynamic changes in SOC and number of microbes in the surface soil after the rainfall within a short time period (10 days) as affected by rainfall and the resultant soil erosion with the aid of quantitative Polymerase Chain Reaction (qPCR) technology. On such a basis, relationship between soil microbes and SOC was analyzed, so as to provide some fundamental theoretical basis for the exploration of the role of soil microbes in SOC dynamics as affected by soil erosion. Results show that:(1) Simulated rainfall had significant effects on the distribution pattern of soil organic carbon in the slope and soil profile ? The changes were distinctive under different rainfall intensity, and low intensity rainfall was more conducive to accumulation of soil organic carbon on lower slope. Under soil erosion, rainfall intensity and soil properties have a significant impact on migration and distribution of SOC.(2) The distribution of TN and TP in the soil slope and profile also influenced by soil erosion, after the rainfall TN and TP content were increased in surface soil. By the impact of water infiltration the TN and TP content in deep soil were also changed in varying degrees. Soil moisture content has a significant increase, while soil mechanical composition basically unchanged after the rainfall.(3) Rainfall erosion significantly changed the distribution pattern of the number of microorganisms on the slope of the surface soil. After the rain, SOC content and the number of bacteria and fungi all significantly increased and peaked within a short time period, and then decreased, however, the peaks of the three appeared differently in time, which may be attributed to the difference between bacteria and fungi in multiplication rate and magnitude. In addition, correlation analysis shows that rainfall erosion disturbed greatly the relationships of SOC with soil bacteria and fungi, as a result, the post-rainfall relationships of SOC with soil bacteria and fungi in different sections.In a word, soil erosion does not only directly affect SOC distribution in soil, but also alter soil properties, and then changed microbial life activities to indirectly affect organic carbon in soil. And soil erosion also alter the abundance and activity of soil microbes and hence further influence SOC decomposition and mineralization. Therefore, more attention should be paid to the role of soil microbe in global carbon recycling as affected by soil erosion, and more efforts should be devoted in future to studies on dynamics of soil microbes and SOC in soils under different extents of soil erosion with foci on specific role of soil microorganisms in SOC dynamics and related microscopic mechanism. |
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