Characterization of Microbial Communities and Soil Organic Carbon Degradation Associated with the Depth and Thawing Effects on Tundra Soil in Alaska

Abstract

In high-latitude regions, temperature has risen (0.6°C per decade) and this leads to the increase in microbial degradability against soil organic carbon (SOC). Furthermore, the decomposed SOC is converted into green-house gases (CO2 and CH4) and their release could further increase the rate of climate change. Thus, understanding the microbial diversity and their functions linked with SOC degradation in soil-thawing model is necessary. In this study, we divided tundra soil from Council, Alaska into two depth regions (30-40 cm and 50-60 cm of depth, designated as SPF and PF, respectively) and incubated that for 108 days at 0°C. A total of 111,804 reads were obtained through a pyrosequencing-based metagenomic study during the microcosm experiments, and 574-1,128 of bacterial operational taxonomic units (OTUs) and 30-57 of archaeal OTUs were observed. Taxonomic analysis showed that the distribution of bacterial taxa was significantly different between two samples. In detail, the relative abundance of phyla<em> Actinobacteria </em>and <em>Firmicutes</em> largely increased in SPF and PF soil, respectively, while phyla <em>Crenarchaeota </em>was increased in both soil samples. Weight measurement and gel permeation chromatography of the SOC extracts demonstrated that polymerization of humic acids, main component of SOC, occurred during the microcosm experiments. Taken together our results indicate that these bacterial and archaeal phyla could play a key function in SOC degradation and utilization in cold tundra soil.