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在陆地生态系统中,深层土壤是重要的有机碳库.外源碳输入可改变土壤有机碳(SOC)矿化速率(激发效应),进而影响土壤碳排放.然而深层土壤对外源碳输入的响应程度和方向如何还不清楚,引起激发效应的机理尚不明确.本文利用13C标记葡萄糖添加试验,分析亚热带森林不同层次SOC矿化的激发作用,并通过微生物决策群落(r-K策略者)的相对变化来探讨激发效应的机理.结果表明:深层土壤矿化速率显著低于表层土壤,添加标记葡萄糖后能增加所有层次土壤原有SOC的矿化(正激发效应),但是深层土壤的激发效应强度(156%)显著高于表层土壤(45%).葡萄糖添加显著降低了各层次土壤微生物的最大比生长速率,表明r策略者相对比例下降而K策略者相对比例增加.推测SOC矿化的正激发效应主要由K策略者的相对比例变化引起.此外,葡萄糖添加后可溶性有机碳和可溶性氮的比值在深层土壤中(76.03)显著高于表层土壤(13.00),暗示深层土壤存在更为强烈的氮限制作用.深层土壤微生物为获取氮源,可能会加剧对原有SOC的矿化,进而产生更强烈的激发效应.深层土壤SOC矿化受碳源和氮源的限制,更容易受外源碳输入的影响,对未来气候变化也更敏感.
In terrestrial ecosystems, deep soil is an important organic carbon pool. Exogenous carbon input can change soil organic carbon (SOC) mineralization rate (stimulating effect), thereby affecting soil carbon emissions. However, the response of deep soil to external carbon inputs The mechanism of the stimulating effect is not yet clear.In this paper, the 13C labeled glucose addition test was used to analyze the effects of SOC mineralization on the different layers of subtropical forests and the relative changes of microbial community (rK strategist) The results showed that the mineralization rate of deep soil was significantly lower than that of surface soil, and the addition of labeled glucose increased the mineralization (positive excitation) of original SOC in all soil layers, but the excitation intensity 156%) was significantly higher than that of the topsoil (45%). Glucose addition significantly reduced the maximum specific growth rate of soil microorganisms at all levels, indicating that the relative proportion of r strategy decreased while the relative proportion of K strategy increased. The effect was mainly due to the relative change in the proportion of K strategists.In addition, the ratio of soluble organic carbon to soluble nitrogen after glucose addition was higher in deep soil (76.03) was significantly higher than that of surface soil (13.00), suggesting that there was a stronger nitrogen limitation in deep soil. In order to obtain nitrogen source, deep soil microorganisms may exacerbate the mineralization of the original SOC and produce more intense excitation Effect of deep soil SOC mineralization is more restricted by the input of exogenous carbon and more sensitive to the future climate change due to the limitation of carbon and nitrogen sources.