[目的]黄土高原水蚀风蚀交错区是典型的脆弱生态系统，该区域生物结皮广泛分布，生物结皮在土壤有机碳积累与转化发挥着关键作用，然而，生物结皮演替及微生物对土壤有机碳转化相关酶类的影响规律尚不明确。[方法]研究土壤有机碳-微生物-碳转化相关酶在生物结皮不同演替类型的变化规律，并运用SEM模型分析了三者之间的相互关系。[结果](1)生物结皮演替显著增加土壤有机碳含量和碳转化相关酶活性，且它们在结皮层(0-2 cm)中的含量均显著高于裸沙和2-5 cm 土层(p＜0。05);(2)结皮层细菌、真菌和放线菌数量在藓结皮中最高，其中放线菌、真菌数量在生物结皮演替呈显著增加趋势，结皮层中的细菌和真菌数量显著高于2-5 cm 土层，但2-5 cm 土层放线菌数量高于结皮层(藓结皮除外);(3)SEM模型表明，土壤有机碳、碳转化相关酶活性和微生物数量之间均呈现显著相关性。[结论]生物结皮的演替对土壤有机碳的积累为碳转化相关酶类和微生物提供丰富基质，促进微生物和酶活性提高，微生物对碳转化相关酶类起着重要的驱动作用，对维持生物结皮的碳平衡发挥着关键作用。
Effects of Different Biocrust Types on Soil Organic Carbon and Its Transformation in the Water-wind Erosion Crisscross Region of the Loess Plateau
[Objective]Wind-water erosion crisscross region in Loess Plateau is a typical fragile ecosystem.Biological soil crusts(BSCs)are widely distributed in this region and play key roles in the accumulation and transformation of soil organic carbon(SOC).However,the effect of BSCs succession and microorganisms on enzymes related to organic carbon conversion is still unclear.[Methods]In this manuscript,SOC contents,microbial number and enzymes related with carbon conversion in different BSCs types were investigated.The relationships among SOC,microbial number and enzume activities related with carbon conversion were also analyzed by SEM model.[Results](1)BSCs succession significantly inceased SOC content and enzyme activities related with carbon conversion.SOC and enzyme activities in BSCs layer(0-2 cm)were significantly higher than those in bare sand 2-5 cm soil layer(p＜0.05).(2)The number of bacteria,fungi and actinomyces in moss crusts was the highest,and the number of fungi and actinomyces significantly increases with BSCs succession.Bacteria and fungi in the BSCs were significantly higher than those in 2-5 cm soil layer.However,actinomycetes in BSCs(except moss crusts)were lower than 2-5 cm layer.(3)SEM model indicated that SOC,enzyme activities and microbial number showed significant correlation.[Conclusion]The accumulation of SOC by BSCs succession provided a rich substrate and nutrients for enzymes related with carbon conversion and microbes,which were helpful for the increase of microbes and improvement of enzyme activities related with carbon conversion.Microbes play critical roles in driving enzyme activities related with carbon conversion and maintaining carbon balance in BSCs.
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