Taxonomic reconstruction of paleovegetation from 138 permafrost metagenomes connects ancient plant communities to modern conditions in permafrost

Background/Question/Methods

Permafrost, or perennially frozen ground underlies 24% of the land in the Northern Hemisphere. Permafrost preserves vast amounts of carbon in the form of ancient plant detritus. Climate change is currently thawing permafrost, making this carbon available to permafrost microbial communities, who degrade it and release globally significant amounts of greenhouse gasses. The characteristics of permafrost carbon, its susceptibility to degradation, and the structure of microbial communities that inhabit permafrost are likely strongly influenced by the vegetation present (and thus the detrital material) at the time the permafrost formed. To reconstruct paleovegetation from permafrost samples ranging in age from approximately 2000 to 800,000 years old, we mined 138 permafrost metagenomes for DNA sequences originating from plant material and performed taxonomic reconstructions and statistical modeling.

Results/Conclusions

Plant taxa have been identified and have revealed patterns of change in response to the last ice age. Ongoing analysis is revealing evidence that paleovegetation influences site geochemistry and microbial communities, and that the taxonomic richness of ancient plant communities is positively correlated to modern soil nitrogen and organic carbon content. Understanding the contribution of paleovegetation to permafrost may shed light on the vulnerability of permafrost soils to climate change, and aid in predicting their contribution to climate change.