高寒森林溪流微生物群落结构的季节性变化

高寒森林溪流不仅是区域河流的源头,而且是联系陆地与水域的生态纽带。微生物活动可能成为控制溪流生态系统过程的关键因子,但其结构与动态过程缺乏必要关注。因此,结合同步温度动态监测,采用实时荧光定量PCR和DGGE技术,在2014年到2015年冻融季节和生长季节关键时期对比研究了川西高寒森林溪流和森林林下土壤中微生物群落的动态特征。研究结果发现,高寒森林溪流具有较低的真菌和细菌群落丰度;与森林土壤相同,溪流在冻融季节表现出相对生长季节更高的真菌/细菌比,而且从冻融季节到生长季节,溪流微生物丰度动态也表现出明显的季节性变化特征。与森林土壤不同的是,溪流中细菌和真菌的丰度及其Shannon-Wiener多样性指数的最高值均出现在生长季节而不是冬季冻融季节,并且溪流中细菌丰度在季节性变化的不同时期具有显著差异(P0.05)。此外,森林土壤细菌类群以芽孢杆菌属(Bacillus sp.)比例相对较高,真菌类群则以格孢菌属(Pleosporales sp.)、曲霉属(Aspergillus sp.)和其他一些子囊菌门(Ascomycota)的类群为优势;而溪流细菌类群以红球菌属(Rhodococcus sp.)为主,真菌类群则以曲霉属和空团菌属(Cenococcum sp.)为主。同时,季节性变化中温度、p H、水溶性有机碳和溶解氧等环境因子可显著影响溪流微生物群落结构及其组成,这些环境因子在高寒森林溪流微生物群落的季节性变化过程中具有重要的作用。

Seasonal variation of microbial community in forest streams of the high-frigid area

Forest streams in the high-frigid areas are not only the source of water for regional rivers, but they also play important roles in the ecological linkage between land and water areas. Since relative low temperature could limit the activity and productivity of microorganisms, the organism structure in the steams is relatively homogeneous, although microbial activity could be the key ecological factor regulating the ecological processes of stream ecosystem. Moreover, the available information about the structure and the dynamic processes of the microbial community has not been sufficiently documented in the high-frigid forest streams. Therefore, the structural dynamics of microbial community were investigated both in soil and streams in a coniferous forest in western Sichuan, China. Real-time fluorescent quantitative PCR and denatured gradient gel electrophoresis (DGGE) were used. Environmental factors such as temperature, pH, dissolved organic carbon, dissolved oxygen, and stream water conductivity were also monitored at different seasonal stages in the freezing-thawing and the growing seasons from 2014 to 2015. The results showed that the microbial abundance observed in streams was relatively lower than that in soil at each key period throughout the year. The ratio of fungi to bacteria was higher in winter than in the growing season in both streams and soil. The microbial abundance and community diversity showed similar dynamic patterns both in streams and soil. In contrast, the peak of microbial abundance and Shannon-Wiener diversity index in streams appeared in the growing season, whereas in soil, this was in the winter. Moreover, there were significant differences in the bacterial abundance in each key period in streams. Furthermore, the results from sequencing analysis revealed that the main bacterial species in streams was Rhodococcus sp., but in soil, it was Bacillus sp. The main fungal species in streams were Aspergillus sp. and Cenococcum sp., whereas Pleosporales sp., Aspergillus sp. and some other Ascomycota were the main ones in soil. In addition, the environmental heterogeneity, seasonal changes, and microenvironmental factors (e.g., temperature, pH, and nutrient availability such as dissolved organic carbon and dissolved oxygen) showed substantial effects on microbial community structure and composition in streams in the high-frigid forest.