Impact of long-term fertilizer and summer warming treatments on bulk soil and birch rhizosphere microbial communities in mesic arctic tundra

ABSTRACT

Recent climate warming in the Arctic is enhancing microbial decomposition of soil organic matter, which may result in globally significant greenhouse gas releases to the atmosphere. To better predict future impacts, bacterial and fungal community structures in both the bulk soil and the rhizosphere of Arctic birch, Betula glandulosa, were determined in control, greenhouse summer warming, and annual factorial nitrogen (N) and phosphate (P) addition treatments twelve years after their establishment. DNA sequence analyses at multiple taxonomic levels consistently indicated substantial bulk soil and rhizosphere microbial community differences among the fertilization treatments but no significant greenhouse effects. These results suggest that climate warming will likely increase the activity rates of soil microbial decomposers but without substantially altering the structure of either the bacterial or fungal communities. Differential abundance testing revealed changes in ectomycorrhizal fungal species of the genus Thelephora in both bulk soil and rhizosphere, with increases in their relative abundance in P and N + P amended plots compared with warming and controls. Because birch is the principal low Arctic ectomycorrhizal host, our results suggest that these fungi may promote this shrub’s competitiveness where tundra soil nutrient availability is enhanced by warming or other means, ultimately contributing to arctic vegetation “greening.”

KEYWORDS:

• Climate change
• nitrogen and phosphate fertilization
• Betula glandulosa
• ectomycorrhizal fungi
• soil community diversity

Acknowledgments

We acknowlege the excellence of the Centre for the Analysis of Genome Evolution & Function (CAGEF) at the University of Toronto and, in particular, Dr. D. Guttman and Julia Copeland. We thank Qian Gu for assistance with the fieldwork and K. Moniz for her valuable technical expertise. We acknowledge anonymous reviewers for their comments.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Funding

This research was supported by funding from the Natural Sciences and Engineering Research Council (NSERC) of Canada Discovery grants to V.K.W. and P.G.

Supplementary material

Supplemental material for this article can be accessed on the publisher’s website.