Study: Rising Atmospheric CO2 Is Reducing Nitrogen Availability in Boreal Forests
Key Takeaways
- ▸Rising atmospheric CO2 is the primary driver of declining nitrogen availability in boreal forests, not nitrogen deposition changes as previously debated
- ▸The oligotrophication effect was observed consistently across Sweden regardless of latitude or regional nitrogen deposition variations
- ▸These findings have significant implications for understanding the future role of boreal forests as carbon sinks in the global carbon cycle
Summary
A comprehensive study of Swedish boreal forests spanning 1961 to 2018 has found that elevated atmospheric carbon dioxide levels are causing declining nitrogen availability across forest ecosystems, a phenomenon known as oligotrophication. Researchers analyzed nitrogen isotope chronologies from tree rings across Sweden's 23.5-million-hectare forest area, which spans a 1,500-kilometer latitudinal distance with varying nitrogen deposition rates but uniform rising CO2 levels. The study's statistical models identified rising CO2 as the strongest predictor of declining nitrogen availability, outweighing factors like nitrogen deposition, temperature, and forest basal area. This finding was particularly evident in northern forests where atmospheric nitrogen deposition is already very low, suggesting a direct link between CO2 and reduced nitrogen cycling.
- The research resolves a scientific disagreement about whether CO2 or temporal N deposition changes explain nitrogen availability patterns in forest ecosystems
