Mosses and their associated microbes are critical components of nutrient cycling in arctic ecosystems, yet many aspects of these communities are poorly understood. Moss-associated microbes are the major source of nitrogen to support plant growth in boreal and tundra ecosystems, meaning that rates of plant growth may be highly sensitive to the activity of mosses and their microbes, which "fix" nitrogen from the atmosphere into a form useful for plant growth. Importantly, the rates of nitrogen fixation depend in complex ways upon both the genetic diversity of the mosses and their associated microbial communities (microbiomes). However, we do not know which species (moss or microbial) are responsible for rate variation in this key biogeochemical process of nitrogen fixation, nor how these communities will function respond to a warming climate. This work will test for associations between genetic variation and nitrogen fixation in order to model the response of high northern latitude biodiversity and ecosystem function to climate change. The research will provide instrumental information about how environmental change will affect Arctic ecosystems and contribute insight into the resiliency of mosses and their associated microbiomes.
The goal of the proposed work is to determine the effect of moss genetic diversity on the community assembly and function of the N-fixing microbiomes of two widespread and abundant mosses in boreal forest and arctic tundra ecosystems. The researchers will employ population genomics, functional gene sequencing, and stable isotope assays of N fixation rates along a large-scale climate gradient in Alaska that includes arctic and boreal Long-term Ecological Research (LTER) and National Environmental Observatory Network (NEON) sites. This interdisciplinary approach will enable the researchers to determine both the historical and contemporary drivers of variation in community assembly and function of this rapidly changing ecosystem, and predict how bryophyte-associated nitrogen fixation will change in a warmer climate. Thus the researchers will use moss-microbe interactions in high latitude systems as a model to inform our broader understanding of how biodiversity interacts with ecosystem function in the context of a changing climate.