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    Changes in soil microbial biomass carbon and enzyme activities under elevated CO2 affect fine root decomposition processes in a Mongolian oak ecosystem

    论文题目: Changes in soil microbial biomass carbon and enzyme activities under elevated CO2 affect fine root decomposition processes in a Mongolian oak ecosystem
    第一作者: Xuefeng Li
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    发表年度: 2010
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    Abstract:

    The relationships between soil microbial properties and fine root decomposition processes under elevated CO2 are poorly understood. To address this question, we determined soil microbial biomass carbon (SMB-C) and nitrogen (SMB-N), enzymes related to soil carbon (C) and nitrogen (N) cycling, the abundance of cultivable N-fixing bacteria and cellulolytic fungi, fine root organic matter, lignin and holocellulose decomposition, and N mineralization from 2006 to 2007 in a Mongolian oak (Quercus mongolica Fischer ex Ledebour) ecosystem in northeastern China. The experiment consisted of three treatments: elevated CO2 chambers, ambient CO2 chambers, and chamberless plots. Fine roots had significantly greater organic matter decomposition rates under elevated CO2. This corresponded with significantly greater SMB-C. Changes in the activities of protease and phenol oxidase under elevated CO2 could not explain the changes in fine root N release and lignin decomposition rates, respectively, while holocellulose decomposition rate had the same response to experimental treatments as did cellulase activity. Changes in cultivable N-fixing bacterial and cellulolytic fungal abundances in response to experimental treatments were identical to those of N mineralization and lignin decomposition rates, respectively, suggesting that the two indices were closely related to fine root N mineralization and lignin decomposition. Our results showed that the increased fine root organic matter, lignin and holocellulose decomposition, and N mineralization rates under elevated CO2 could be explained by shifts in SMB-C and the abundance of cellulolytic fungi and N-fixing bacteria. Enzyme activities are not reliable for the assessment of fine root decomposition and more attention should be given to the measurement of specific bacterial and fungal communities.

    Keywords: Elevated CO2; Fine root decomposition; Soil microbial biomass carbon; Soil microbial biomass nitrogen; Enzyme activities; Mongolian oak


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