Nitrogen Cycling in Boreal Forests: A window into the past and future.

Boreal forests are responsible for the uptake of a significant portion of human CO2 emissions.

During the past century boreal forest growth has increased, due to climate change and management; however, it remains highly uncertain whether their C sink strength will continue to increase in the future.

Their C sink strength may asymptote or decline if key resources forests depend on become more limited, in particular nitrogen (N).

It is speculated that higher CO2 may cause N availability to progressively decline over time, and it remains unknown whether biological N2 fixation will increase under future climates to satisfy higher N demand.

The aim of our proposed research is: a) to identify whether N availability to boreal forests has already declined; and, b) determine whether biological N2 fixation will change under future climates.

In order to look back in time, we will use a unique tree core archive collected by the Swedish National Forest Inventory (NFI) spanning 6 decades to assess whether N availability has changed on the Swedish forest landscape.

In order to look ahead in time, we will measure biological N2-fixation rates within a unique experimental infrastructure designed to simulate future climates.

Together, these two projects will provide a perspective on the N cycle from the past into the future, which is in critical demand by the scientific community in order to effectively model the global C cycle, and predict the rate of global warming.