上海崇明东滩两种典型湿地土壤有机碳汇聚能力差异及成因

通过分析上海崇明东滩南部冲刷带芦苇型砂壤土(A区)和东北部淤涨带芦苇/米草型粘土(B区)的有机碳含量和植被输入量，研究了异质性湿地土壤的有机碳汇聚能力，并从异质型土壤的微生物活性和理化性质的差异角度分析了造成土壤有机碳汇聚能力差异的主要原因.结果表明：A区土壤平均总有机碳含量仅为B区的46.10%(P<0.05)，而A区地上部分的年均植物量仅比B区低9.16%，说明A区湿地土壤有机碳的输出量大于B区.A区细菌总数比B区高3.82倍(P<005)，过氧化氢酶和转化酶活性分别比B区高4681%和3433%(P<0 05)，且土壤微生物呼吸强度也高于B区.说明A区土壤的微生物碳代谢能力较强是导致其土 壤有机碳保留能力较弱的重要原因.A区砂壤土粒间孔隙较大、土壤通气透水性较好、含水 率与含盐量较低，有利于微生物生长，促进了土壤有机碳的分解;而B区的芦苇/米草型粘 土的含水量和含盐量高、微生物活性弱，有机碳氧化分解能力较低，具有较高的有机碳汇聚 能力.

Difference and its formation cause in soil organic carbon accumulation capability of two typical tidal wetlands at Dongtan of Chongming Island in Shanghai.

Through the analyses of soil organic carbon content and vegetation inp ut, this paper studied the difference in soil organic carbon accumulation capabi lity of two typical tidal wetlands, one (A) was on the erosion bank with Phragmites communis and sandy loam soil at southeast Dongtan in Shanghai, and the other (B) was on the alluvial bank with P. communis, Spartina alterniflora, and c lay soil at northeast Dongtan of Chongming Island. The main formation causes of the difference were analyzed based on the determinations of soil microbial activ ities and physical-chemical properties. In A, the average soil total organic ca rbon content was 4610% (P<005) of that in B, while the annual abovegro und vegetation dry mass was only 916% lower than that in B, illustrating that the soil organic carbon output was higher in A than in B. The total count of soi l bacteria and the activities of soil catalase and invertase in A were 3.82 time s (P<005), 4681% (P<005), and 3433% (P<005) higher than th ose in B, respectively, and the soil microbial respiration in A was also higher than that in B, which indicated that the stronger soil microbial C- metabolic a ctivity in A was the main cause inducing the lower soil organic carbon accumulat ion capability. The sandy loam soil in A had higher porosity and lower salinity and moisture, being favorable to the growth of soil microbes and the decompositi on of soil organic carbon, while the clay soil in B had higher salinity and mois ture but lower microbial activity, leading to the weaker soil organic carbon dec omposition and higher organic carbon accumulation.