Effect of land use and cover change on soil organic carbon fractions and enzymatic activities in lakeshore wetland of north shore of Lake Chaohu

Abstract

为了揭示湖滨带土地利用与覆被改变对土壤有机碳库及生态功能的影响，本文选取了巢湖湖滨带（北岸）9个典型样方，分析和比较了表层（0~30 cm）土壤有机碳组分特征以及相关酶的活性.结果表明，巢湖湖滨带不同采样点土壤总有机碳（TOC）含量变化范围为2.88~11.2 g/kg，平均含量为9.12 g/kg，其中原生芦苇（Phragmites australis）湿地土壤TOC含量最高（11.2 g/kg），而芦苇群落消失后形成的荒滩土壤TOC含量最低，仅为2.88 g/kg.表征湖滨带湿地缓冲性能的土壤阳离子交换量（CEC）也以原生芦苇湿地土壤为最高，并与TOC含量呈现明显正相关.湖滨带表层土壤溶解性有机碳（DOC）和易氧化有机碳（EOC）含量变化范围分别为150~370 mg/kg和1.7~5.2 g/kg，其变化幅度明显高于TOC，其中DOC含量各采样点差异最为显著.除多酚氧化酶外，次生水柳林（Homonoia riparia Lour.）表层土壤几种酶的活性较原生芦苇湿地土壤皆有所上升，特别是蔗糖酶活性增加幅度最为明显.受人类活动干扰较大的湖滨绿地公园和人工草滩土壤过氧化氢酶、脲酶和蔗糖酶酶活性普遍显著低于原生芦苇湿地.除多酚氧化酶外，土壤中几种酶活性与土壤有机碳组分EOC和DOC含量均呈现显著的正相关，其中蔗糖酶活性与DOC含量之间相关系数最高（r=0.907），其相关性均达到极显著水平.土壤溶解性有机碳和蔗糖酶可以作为表征因土地利用与覆被变化导致湖滨带湿地退化以及生态恢复效果的敏感性指标.;In order to explore the effect of land use and cover change on lakeshore soil organic carbon sequestration and it ecological function, nine typical sample plots with different plantations along the north shore of Lake Chaohu were investigated, and the surface soils (0-30 cm) organic carbon fractions and the enzymes activities were analyzed and compared. The results showed that soil total organic carbon (TOC) was 2.88-11.2 g/kg, with an average of 9.12 g/kg. The soil under native Phragmites australis reed wetland showed the highest TOC content, and the TOC content in the wasteland formed after the disappearance of P. australis reed community was the lowest with the value of only 2.88 g/kg. The cation exchange capacity (CEC), which can be used to characterize the buffer performance of lakeside zone, was highest in the native P.australis reed wetland soil and positively correlated with TOC. Soil labile organic carbon fractions content, including dissolved organic carbon (DOC) and easily oxidized organic carbon (EOC) from the lakeshore wetland, ranged from 150 to 370 mg/kg and from 1.7 to 5.2 g/kg, respectively. The range of change in soil DOC and EOC between different sampling sites was larger than that in TOC. Especially, the difference of DOC content between different vegetations was the most significant. The activities of several determined enzymes in the surface soil of secondary Homonoia riparia Lour. Forest, except polyphenol oxidase, were higher than those in native P. australis reed wetland soil. Especially, the invertase activity increased most obviously. However, lakeshore urban green park and artificial grassland showed significantly lower activities of catalase, urease and invertaseas compared with native P. australis wetland. Correlation analysis showed that there existed significant relationships between soil enzyme activities except polyphenol oxidase and soil DOC and EOC. Especially, the correlations of invertase activity to the content of DOC reached remarkably significant level with the highest coefficient (r=0.907). Based on the above results, it is concluded that the DOC and invertase as the sensitive indicators, could well characterize the degradation process and ecological restoration effect on lakeshore wetland buffering function due to land use and cover change.