天山一号冰川底部沉积层及其前沿退缩带微生物群落时空演替格局对环境分异的响应

近二十年来，全球气候变暖使冰川呈现加速融化和退缩趋势，但目前对冰川退缩前后生态系统发生的微生物地球化学过程缺乏全面的比较研究。我们前期研究发现天山一号冰川前沿生境具有明显的时间序列性和空间异质性，其微生物类群空间分布格局明显不同于高纬度极地环境。本项目拟采用不同分辨率的分子生物学技术(克隆文库、定量PCR、高通量测序)，结合土壤理化特征、功能酶活等分析，系统开展中、低纬度典型冰川退缩前后生境微生物群落时空演替的模式研究。通过处理海量DNA序列数据结合生态多元统计：揭示一号冰川底部沉积层及其退缩前沿微生物群落在不同分类学层次上的空间分布格局，尤其阐明高层次微生物分类单元是否对环境异质表现出生态凝聚力；揭示介导碳、氮、硫循环的功能微生物类群在退缩过程中的演替规律及其对环境分异的响应机制。为比较和科学评价全球不同冰川退缩生态系统微生物地球化学过程差异，以及为区域环境变化趋势的预测提供理论依据。

Microorganisms are the most abundant and potentially most diverse organisms in the biosphere. They play critical roles in many ecosystem processes and thereby control key pathways of biogeochemical cycling. However, to date, knowledge of the origin, maintenance and distribution of diversity on terrestrial microorganisms remains limited. .Forefields of receding glaciers are pristine and sensitive environments representing natural chronosequences and the spatial heterogeneities. One consequence is the acceleration of glacier retreat, exposing new habitats that are colonized by microorganisms whose diversity and function are unknown. Thus，these glacier forefields provide excellent opportunities to study microbial succession, biogeochemical weathering processes, and the conversion of glacial till into fertile soils along the chronosequence in regionally defined landscape..The objective of this project is to use a combination of culture-independent methods, namely rRNA gene clone library analyses，pyrosequencing , DGGE fingerprinting，quantitative PCR (q-PCR), to determine the microbial diversity and community composition present within the supra-, sub-, and proglacial sediments of the Glacier No.1 in the Tianshan Mountains. A comparison of multiple microbial community along a chronosequence of a glacier forefield is carried out by using phylogenetic-diatance based approaches and the UniFrac software. In addition, multivariate analysis of ecological data will be used to demonstrate the geographical distrubation patterns of phylogenetic groups of the Glacier No.1 foreland soils at different level of taxonomic organization. .To conclude, our objectives are: (ⅰ) to test whether the deeper branches of the ribosomal RNA-derived phylogenetic tree in the pristine terrestrial systems, such as the phyla or class level, have ecological coherence. (ⅱ) to determine whether the subglacial microbiota are allochthonous (originating from adjacent environments) or autochthonous (indigenous communities unique and potentially adapted to the subglacial environment). (ⅲ) to link environmental variables to shifts in the structure and composition of the microbial community, and to investigate whether, or to what extent, environmental variables that vary over space and time induce succession of the nitrogen, carbon and sulfur cycling microbial communities. .The implementation of the project contributes greatly to our understanding of how the ecosystem prosesses of receding glaciers varies in response to global climate change, and thereby possibly shedding light onto the tendency of environmental changes in a regionally defined landscape.