川西亚高山/高山森林土壤微生物对季节性冻融的响应

Soil microbe responses to seasonal freeze-thaw in the subalpine/alpine forests of western Sichuan

通过研究川西亚高山/高山森林矿质土壤层微生物群落丰度和结构在季节性冻融期间的变化,可为深入认识亚高山/高山森林冬季土壤生态过程提供理论依据.于2009年8月至2010年8月,在植物生长季节、土壤冻结阶段(包括土壤冻结期和土壤深冻期)和土壤融化阶段(包括土壤融冻期和土壤融化后期),采用变性梯度凝胶电泳(PCR-DGGE)和实时定量PCR技术同步研究不同海拔冷杉次生林(3 023 m)、天然混交林(3 298 m)和岷江冷杉原始林(3 582 m)矿质土壤层微生物类群的变化特征.结果显示,随着土壤冻结的开始,土壤细菌数量显著降低(P<0.05),而在随后的融化过程中又显著升高;土壤真菌数量具有和细菌数量相似的变化趋势,在融化阶段显著升高;土壤古菌数量在土壤冻结阶段得到升高,表现出与细菌数量相反的变化趋势.并且,Shannon-Wiener指数(H)随森林类群的变化而变化,在土壤冻结阶段,细菌H主要表现为3 582 m处<3 298 m处<3 023 m处,古菌H表现为3 298 m处<3 023 m处<3582 m处,真菌H表现为3 023 m处<3 582 m处<3 298 m处;而在土壤融化阶段3种菌落的H均表现为3 582 m处<3 023m处<3 298 m处.综上,季节性冻融期间强烈的环境变化极大地影响了土壤微生物群落的数量和结构,但不同微生物类群在不同海拔表现出一定的差异.

Soil microbes are very sensitive to environmental changes. However, little information is available on soil microbial community during the seasonal freeze-thaw in the alpine forests. This paper aimed to determine the variations of the abundance and structure of microbial community in mineral soil （MS） at different altitudes over a freeze-thaw season in the typical subalpine/alpine forests of western Sichuan of China. PCR- DGGE and Real-time qPCR were used to measure the structure and abundance of soil microbial community, respectively, in three typical forests along an altitude gradient （3 023, 3 298 and 3 582 m）. The results showed bacterial and fungal rDNA copy numbers decreased from growing season to freezing stage and then increased in the thawing stage. The archaeal rDNA copy numbers increased in the freezing stage. Similarly, the diversity of microbial community varied with seasonal freeze-thaw processes. Shannon-Winner richness varied greatly with the elevation, with the bacterial H of 3 582 m 〈 3 298 m 〈 3 023 m, archaeal H of 3 298 m 〈 3 023 m 〈 3 582 m and fugal H of 3 023 m 〈 3 582 m 〈 3 298 m during the soil freezing stage. In the soil thawing stage, the three microbial H was 3 582 m 〈 3 023 m 〈 3 298 m. Our results suggested that the abundance and structure of soil microbial community in the coniferous forests varied by season. This may have important implications to understanding the winter time ecological process in soils.