土壤侵蚀是土壤有机碳（Soil organic carbon，SOC）动态过程的重要驱动因素，明确土壤侵蚀如何影响土壤微生物进而作用于SOC，有助于准确把握土壤侵蚀在全球碳循环中的作用。通过野外径流小区模拟降雨试验，结合定量聚合酶链式反应（quantitative Polymerase Chain Reaction，qPCR）技术，研究了水力侵蚀后短期内（10 d）坡耕地表层土壤微生物数量和SOC含量动态变化特征，并在此基础上探讨了微生物与SOC间的关系。结果表明：与雨前相比，降雨侵蚀后表层土壤SOC含量没有显著差异，而表层土壤细菌数量显著降低，为雨前细菌数量的58.76%（坡上）、55.22%（坡中）、55.82%（坡下）；降雨侵蚀同样显著改变了表层土壤真菌数量，雨后真菌数量为雨前真菌数量的105.51%（坡上）、2.29%（坡中），12.20%（坡下）；降雨侵蚀后，SOC、细菌和真菌数量均在短时间内显著增加，达到峰值后下降；相关性分析表明，细菌和真菌数量与SOC之间的关系均未表现出显著正相关关系，仅有坡下细菌，坡中、坡下以及整个坡面真菌与SOC含量表现出显著正相关关系。
Soil erosion is an important driving factor of soil organic carbon (SOC) dynamics and plays an extremely important role in the long-standing problem of "missing of carbon sink". Transport and deposition of soil particles on the earth’s surface triggered by soil erosion cause variation of soil microbes in distribution with the position of soil erosion. which in turn affects carbon sequestration and mineralization on the soil. Therefore, it is necessary to figure out how soil erosion affects soil microorganisms and then acts on soil organic carbon. The knowledge will help understand correctly the role of soil erosion in global carbon recycling A field simulated rainfall experiment was conducted on a runoff plot (2m × 5m) in a red soil hilly region of South China, to study dynamic changes in SOC and number of microbes in the surface soil of the plot 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. The plot was evenly divided into five sections along the slope, namely, A, B, C, D, and E (each 1 m long). Prior to rainfall simulation, soil samples were collected separately from the soil layers (0～10 cm depth) of Sections A (Up slope, US), C (Middle slope, MS), and E (Lower slope, LS) for analysis of basic soil properties. Boreholes left by the samples were immediately filled up with soil from nearby and carefully leveled so as to minimize any possible impact of the sampling on effect of the later rainfall simulation. Soil samples were collected again in the same manner as soon as the simulated rainfall stopped. The second batch of samples were collected 35 h after the rainfall stopped, and then the third, forth ..... batches were at 24 h intervals within the 10 days after the simulated rainfall. The soil samples were all analyzed for basic soil properties and number of soil microbes immediately as they were collected. Results show that after the rainfall, SOC content in the surface soil layer increased in Sections US and MS, but decreased in Section in LS, as a result of rainfall erosion, however, the changes were not significant. Meanwhile, the rainfall and its resultant erosion significantly changed the distribution pattern of soil microbes. The number of soil bacteria in the surface soil layer dropped significantly down to 58.76% (US) , 55.22% (MS) and 55.82% (LS) of that, respectively, before the rainfall, and the number of fungi increased to 105.51% in Section US, and fell to 2.29% in Section MS, and 12.20% in Section LS. After the rain, SOC content number of bacteria and number of 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 varied from what was found in other studies and no positive correlation was found between them, except for the umber of bacteria in Section LS and the number of fungi in Sections MS and LS and the whole runoff plot, which were found positively related to SOC. In a word, soil erosion does not only directly affect SOC distribution on the earth's surface, but 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. However, this experiment was quite limited in simulation of soil erosion. 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.
喻 为,李忠武,黄金权,聂小东,黄 斌,胡延彪,张 雪.水力侵蚀影响下土壤有机碳和微生物数量动态变化特征[J].土壤学报,2015,52(2):423-430. DOI:10.11766/trxb201403100099 Yu Wei, Li Zhongwu, Huang Jinquan, Nie Xiaodong, Huang Bin, Hu Yanbiao, Zhang Xue. Dynamics of soil microbial population and organic carbon under water erosion[J]. Acta Pedologica Sinica,2015,52(2):423-430.复制