洞庭湖湿地有机碳垂直分布与组成特征

Characteristics of Distribution and Composition of Organic Carbon in Dongting Lake Floodplain

以洞庭湖3类湿地的9个典型剖面为代表,研究了洞庭湖湿地有机碳垂直分布和组成特征.结果表明,湖草滩地表层(0～1 0cm)有机碳含量(>4 0g/kg)明显高于芦苇滩地(2 0±2 . 8) g/kg和垦殖水田(2 8±8 . 6 ) g/kg .0～30cm内,湖草和芦苇滩地有机碳含量随深度的增加而下降,30cm以下有机碳含量基本稳定.垦殖水田的3个剖面间有机碳含量存在较大变异.湖草滩地表层0～1 0cm轻组碳占总有机碳的2 0 %以上,而芦苇滩地和垦殖水田表层0～1 0cm的有机碳以稳定的重组碳为主(>90 %) .同一类型湿地垂直方向上,受有机碳来源复杂性的影响,轻组碳占总有机碳的比例具有明显的层次性.分组试验还表明,重组碳与总有机碳、容重与总有机碳、重组碳与重组氮之间具有极显著的相关关系(p <0 . 0 1 ) .

Distribution and composition of organic carbon (OC) at nine soil profiles of three types of wetlands in Dongting Lake floodplain were analyzed.Results show that the OC content at top layer (0～10cm) in Carexspp-dominated floodplain was much higher (>40 g/kg) than that in Phragmites-dominated floodplain (20±2.8)g/kg and paddy soil (28±8.6)g/kg. The OC content decreased with increasing depth from 0 to 30 cm, while it was relatively stable (around 15 g/kg) at depths deeper than 30 cm in Carexspp-dominated and Phragmites-dominated floodplain. However, there was a substantial variability in OC content in paddy soil profiles. In terms of the composition of OC, at top layer (0～10 cm), light fraction carbon in Carexspp-dominated floodplain accounted for more than 20% of the total organic carbon, whereas more than 90% of total organic carbon were heavy fraction that were much more difficult to be decomposed in Phragmites-dominated floodplain and paddy soils. The ratio of light fraction to total organic carbon at the soil profiles was greatly affected by the origin of organic matter. Statistical analyses indicate that there were significant correlations between heavy fraction and total organic carbon, between bulk density and total organic carbon, and between OC and nitrogen in heavy fraction (p<0.01).