鄱阳湖湿地土壤微生物群落结构沿地下水位梯度分异特征

为了揭示地下水位梯度对湿地土壤微生物群落的影响,在鄱阳湖典型碟形湖泊白沙湖洲滩湿地设置了200m×300m大样地,沿地下水位梯度划分4个样带(从湖岸到湖心依次为GT-A,GT-B,GT-C,GT-D),采集了不同梯度带的土壤样品,利用磷脂脂肪酸法分析其土壤微生物群落结构分异特征。结果表明,随着地下水位抬升,土壤pH和沙粒含量升高,而有机碳、容重、粘粒和粉粒含量降低。与地下水位最低的梯度(GT-A)相比,地下水位在地表上下波动(GT-D)时,土壤微生物量碳氮及其分配比例分别增加了2.82、4.30、5.77和7.15倍;土壤微生物总量、细菌生物量、放线菌生物量、革兰氏阳性细菌及革兰氏阴性细菌生物量分别增长了106.8%、117.2%、74.9%,107.9%和207.2%。洲滩地下水位梯度的升高增加了土壤微生物群落的环境压力,进而降低了其群落结构的多样性。土壤微生物群落结构组成与土壤pH、含水量、沙粒含量以及碳氮比呈显著相关关系,而土壤微生物商则主要受pH和土壤质地的影响。以上结果表明地下水位梯度所引起的土壤微环境变化对微生物量、土壤有机碳周转和群落结构均产生了深刻影响。

Variation in the distribution of soil microbial community structure along ground water level gradients in the Poyang Lake Wetland

To reveal the response of soil microbial community structure to the changes of ground water level, a 200m×300m field experimental site was setup in the beach of Baisha Lake, a typical shallow lake of the Poyang Lake Wetlands. This site included 4 ground water levels:GT-A, GT-B, GT-C, GT-D (moving from shore to center). Phospholipid fatty acids (PLFA) analysis was applied to determine the microbial community structure. Results showed when ground water level raised from GT-A to GT-D, soil pH and sand content increased and soil organic carbon (SOC), bulk density, clay and silt particle contents decreased. Compared to GT-A, microbial biomass carbon (MBC), microbial biomass nitrogen(MBN), and their allocation ratio of GT-D were significantly more by 2.82, 4.30, 5.77 and 7.15 time. The abundances of total PLFAs, bacterial, actinomyces, gram-positive bacteria and gram-negative bacteria increased 106.8%, 117.2%, 74.9%, 107.9% and 207.2%. The raise in ground water level enhanced the environmental stress on the microbial community, resulting in a decrease in microbial bio-diversity. Soil pH, moisture, sand contents as well as the C:N ratio have significant correlations with PLFA signatures. Further, the microbial quotient (MBC/SOC) is mainly influenced by soil pH and texture. In summary, the results show significant effects of ground water level on both soil microbial biomass and community structure during the dry season.