不同水分条件沼泽湿地土壤轻组有机碳与微生物活性动态

通过野外实验与室内分析,对三江平原生长季内毛果苔草(Carex lasiocapa)沼泽湿地生物量及0~20cm土壤不同有机碳组分进行观测,分析了不同水分条件下毛果苔草湿地土壤轻组有机碳(LFOC)与微生物量碳(MBC)的变化动态.结果表明,随水位增加毛果苔草群落地上生物量积累明显,与10~20cm积水条件相比,17~30cm水位状况下湿地土壤具有较高的轻组有机质含量与比例.生长季初期冻融过程提高了土壤轻组分(LF)有机碳含量与LFOC含量,之后随植物生长毛果苔草沼泽湿地土壤重组有机碳(HFOC)含量增长快于LFOC,说明毛果苔草沼泽湿地土壤具有较高的重组有机质持有能力.此外不同水位条件下毛果苔草沼泽湿地微生物活性受到土壤有机碳含量影响不同,低水位条件下微生物量碳与SOC呈显著正相关关系(R2=0.859),17~30cm水位条件下二者关系不显著,并且高水位毛果苔草沼泽湿地具有较低的MBC与微生物熵,表明该条件下土壤碳库具有较高的稳定性.

Light fractions of soil organic carbon and microbial activity dynamics in marshes under different water conditions.

The experiment was carried out during the growing season in 2009 in Sanjiang Plain,northeast of China.The soils of 0~20cm layer Carex lasiocapa marshes under different depth of standing water conditions were collected monthly for measuring the active organic carbon fractions.Seasonal dynamic of light fractions of soil organic carbon(LFOC) and microbial biomass carbon(MBC) were studied.Compared to the C.lasiocapa marsh with 10~20cm standing water,the marsh with 17~30cm standing water had higher aboveground biomass,SOC and LFOC content.As the growing season started,freeze-thawing process increased the organic carbon content of light fraction,while after that light fractions accumulated carbon slower than the heavy fractions(HF),indicating that soil characters in C.lasiocapa marsh were beneficial to the maintenance of HF.Besides,water table affected the relation between SOC and microbial activity.SOC was significantly related to MBC under 10~20cm standing water condition(R2=0.859),but under 17~30cm standing water condition the relation was not evident.Besides,the lower MBC and microbial quotient in C.lasiocapa marsh with 17~30cm standing water suggested that higher water table elevated the stability of soil carbon pool.