Identifying new sources of nitrogen fixation in Sweden’s boreal forests

Nitrogen supports forest productivity, and nitrogen supplied to trees primarily originates from biological nitrogen fixation, a process that converts atmospheric nitrogen to plant-available forms.

More than two decades of research in boreal forests has essentially focused on a single niche of nitrogen fixation: mosses.

However, new evidence indicates that mosses only contribute a small fraction of the nitrogen that accumulates in boreal forests, meaning that most fixed nitrogen inputs are from yet unidentified sources.

Identifying the other major niches of nitrogen fixation is crucial for predicting future boreal forest productivity and for identifying conservation priorities.

Moreover, it is unknown how climate change factors may affect other prominent niches of nitrogen fixation, which hinders our ability to make sound, evidence-based decisions about forest management and conservation in Sweden.

This proposed project aims to identify other prominent niches of nitrogen fixation (e.g., leaves, roots, or deadwood) across forest successional gradients from stand initiation to old-growth forest, in harvested and wildfire-origin stands in Sweden and abroad.

Moreover, we will quantify the responses of newly identified niches of nitrogen fixation to climate change factors in controlled experiments.