Long-term warming effects on the microbiome and nitrogen fixation of a common moss species in sub-Arctic tundra

Abstract

Bacterial communities form the basis of biogeochemical processes and determine plant growth and health. Mosses, an abundant plant group in many Arctic ecosystems, harbour diverse bacterial communities that are for instance involved in nitrogen fixation. Global climate change is causing changes in aboveground plant biomass and shifting species composition in the Arctic, but little is known about the response of the moss microbiome. Here, we study the bacterial community associated with the moss Racomitrium lanuginosum, a common species in the Arctic, in a 20-year in situ warming experiment in an Icelandic heathland. We evaluate changes in bacterial community composition and diversity. Further, we assess the consequences of warming for nifH gene copy numbers and nitrogen fixation rates. Our findings indicate an increase in the relative abundance of Proteobacteria and a decrease in the relative abundance of Cyanobacteria and Acidobacteria with warming. The nifH gene copy number decreases, while the rate of nitrogen fixation is not affected. This contradiction could be explained by a shift in the nitrogen fixing bacterial community. Although climate warming might not change the contribution of R. lanuginosum to nitrogen input in nitrogen-limited ecosystems, the microbial community resilience and the nitrogen fixing taxa may shift.

The Total and Active Bacterial Community of the Chlorolichen Cetraria islandica and Its Response to Long-Term Warming in Sub-Arctic Tundra

“…The C. islandica-associated microbiota was found to be markedly different to that of the moss Racomitrium lanuginosum which was studied in the same warming experiment (Klarenberg et al, 2019), further supporting the host-specific selection of bacteria from the environment and symbiotic nature of both bryophyte and lichen holobionts proposed in the recent literature (Aschenbrenner et al, 2016;Holland-Moritz et al, 2018). Specifically, we found that C. islandica harbored a less rich and diverse bacterial community than R. lanuginosum, and the microbiota composition was profoundly different.…”

“…In contrast, the decreased relative abundance and potential activity of Bryocella and Acidiphilium might result in slower degradation of dead lichen material. The genus Acidiphilium showed an increase in relative abundance in a moss microbiome in the same warming experiment (Klarenberg et al, 2019). This suggests that the responses of microbiome components to environmental change are at least in part dependent upon host vegetation identity rather than constituting a direct response of the bacteria themselves to extrinsic environmental factors.…”

Boreal moss-microbe interactions are revealed through metagenome assembly of novel bacterial species

“…Moss microbes contribute around 50% of N inputs to boreal forests, play crucial roles in facilitating C degradation in peatlands, and facilitate host adaptation in degraded landscapes [6]. Moss-associated microbial communities are notably dominated by bacteria from the Proteobacteria, Acidobacteria, Actinobacteria, and Cyanobacteria phyla [7][8][9]. Driven by the pressures of accelerating climate change, boreal ecosystems face a temperature increase of ~2.5ºC before the end of the century, which could alter moss-microbe interactions with major implications for global N [10] and C cycles [11].…”