Effect of reclamation on microbial biomass and activity in peat mire soil around Xingkai Lake in Northeast China.

Over the past few decades, many natural wetlands around Xingkai Lake have been converted to soybean or paddy fields; little is known about how such conversion affects soil microorganisms. This study investigated influence of reclaiming wetland to soybean or paddy field on microbial biomass and activity in peat mire soil around the lake. After reclamation, in 0-5 cm, 5-10 cm, 10-20 cm and 20-30 cm soil layers microbial biomass and activities decreased due to reclamation. MBC (Microbial Biomass Carbon), MBN (Microbial Biomass Nitrogen), MBC/MBN, BR (Basal Respiration) all decreased. But before and after reclamation, microbial biomass decreased with soil depth, seasonal variations of microbial biomass and MBC/MBN were similar, higher in May to June than those in July to September. In 0-5 cm and 5-10 cm topsoil layers in May to July, qCO(2)(Respiration Quotient-qCO(2)) was higher in soybean field than that in paddy field and wetland, both were in water logging; while in August and September logging water was drained up, qCO(2) in paddy field increased dramatically to be higher than that in soybean field and wetland. In 10-20 cm and 20-30 cm subsoil layers, qCO(2) were higher in wetland and paddy field than that in soybean filed from May to September. Changes of plant type, litter amount and quality derived from reclamation influenced the microbial biomass and activity seriously. Moreover, situation of water logging was found to be the key factor influencing microbial activity.