Comparative Study On The Microbial Diversity And Successioninthe Forefield Of Different Glaciers In China

In this century, the global warming causes a rapid retreat of glacier worldwide. Glacier retreat has exposed large virgin area, known as glacier receding forefield, for colonization of plants, animals and microorganisms. At present, there have been extensive studies on the plant and animals succession in this ecosystem, and many researchers also pay more attention to soil microorganisms in glacier forefield. In this paper, using 454 high-throughput sequencing technology, we investigated the soil microbial community structure and variation in the forefield of Laohugou, Qiyi, and Baishuiyulong glaciers. We further analyzed the effects of soil physicochemical properties on the soil microbial community. The major results and conclusion are as follows.1. The total soil carbon(C) and nitrogen(N) contents are very low in the soil of three glacier foreland with the lowest C(0.043mg/g.dw) and N(0.017 mg/g.dw) in the soil of Qi Yi galcier. With the soil exposure time increasing soil C content significantly increase. The N content has no clear correlation with soil exposure time. The soil pH range from 8.60 to 8.19, and show a reduction trend with the soil exposure time increase.2. The soil bacterial community was analyzed using the 454 high-throughput sequencing technology and the results showed that, along a chronosequence, bacterial richness increased in the foreland soils of Laohugou and Qiyi Glaciers, which are continental glacier, while the soil fungal richness decreased. However, bacterial richness decreased in the foreland soil of Yulong glacier that is marine glacier, but soil fungal richness increased. With soil exposure time prolonging, the soil bacterial diversity shows a decrease trend in three glacier forelands; the soil fungal diversity increase in the foreland of Laohugou glacier, but decrease in other two glaciers forelands.3. The investigation of microbial community structure in the 6 soil samples of glaciers foreland revealed that the dominant bacterial phyla include Proteobacteria, Bacteroidetes, Actinobacteria, Verrucomicrobia, Acidobacteria, Chloroflexi, Gemmatimonadetes, Armatimonadetes, and Planctomycetes. Among them, Proteobacteria, Bacteroidetes, Actinobacteria, and Acidobacteria are more dominant and wide distribution taxa. The OP11, TM6, Aquificae, WS6 are the unique bacterial taxa in the soil of Yulong Glacier. Ascomycotina and Basidiomycotina are the common fungal phyla in the three glaciers foreland.4. The common and dominant bacterial classes in the three glacier foreland soils include Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Actinobacteria, Sphingobacteria, Acidobacteria, Gemmatimonadetes, Spartobacteria, Armatimonadia, Planctomycetacia, and Verrucomicrobiae, etc. Nitrospira, Subdivision 3, Thermoprotei, and Chthonomonadetes were not detected in the soil Laohugou Glacier. Bacteroidia and Negativicutes were only detected in the soil of Qiyi Glacier and disappear with the gradual retreat of the glacier.5. In order to understand the bacterial community structure in the soils of glaciers across the world, we further downloaded the high-throughput sequencing datasets of soil bacterial community of seven glacier foreland. The comparative analysis revealed a similar bacterial community structure in the soils of glacier foreland. Proteobacteria, Actinobacteria, Acidobacteria, Bacteroidetes, Chloroflexi, Verrucomicrobia, Gemmatimonadetes, Armatimonadetes, and Planctomycetes are common and dominant bacterial phyla in all ten glacier foreland soils, and Proteobacteria, Bacteroidetes, Actinobacteria are wide distribution taxa. Furthermore, Alphaproteobacteria, Betaproteobacteria, Actinomycete, Deltaproteobacteria, Gammaproteobacteria, Acidimicrobiia, Gemmatimonadete, and Thermoleophilia are common classes. Synechococcophycideae, Chloroflexi, Saprospirae, Sphingobacteria, TM7-1, Solibacteres, Planctomycetia, Armatimonadia, TM7-3, Elusimicrobia, and Chthonomonadetes were not detected in the soils of Mc Murdo Dry Valley. Acidobacteria-6, Phycisphaerae, Lostridia, and Thermomicrobia were not detected in Laohugou glacier forfield. Synergistia, Pla3, and TG3 are the unique taxa in the soils of Mc Murdo Dry Valley.6. The correlation analyses between the soil microbial abundance and soil chemical parameters of the glacier forelands showed that bacterial abundance in the soil of Laohugou galcier were positively correlated to the soil N, C, water content, but negatively correlated with pH value. The soil moisture content and pH value were positively correlated with the fungal abundance, while negatively correlated with the soil N and C. The bacterial abundance in the soil of Qiyi galcier were positively correlated to the soil C, soil moisture content, while negatively correlated with soil N and pH value. The soil fungal abundance werepositively correlated with the soil N, pH value, while negatively correlated with the soil C and moisture content. The soil bacterial abundance in the soil of Yulong galcier were positively correlated to the soil N and pH value, but negatively correlated with the soil C and moisture content. The soil fungal abundance werepositively correlated with the soil C and moisture content, while negatively correlated with the soil N and pH value.