Mind-mapping nitrogen cycling in boreal forests

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Mind-map of nitrogen cycling in boreal forests by the N group and collaborators: Dynamic nitrogen (N) pools processes in a boreal forest. Arrows stand for processes between the pools, red dots mark unknowns in the N cycle, and green dashed lines name ongoing or coming projects to solve some of the questions.

Reactive nitrogen (N) has a key role in the atmospheric chemistry and functioning of boreal forests. After years of studying the complex interactions of N cycling in boreal forests, Janne Korhonen et al. (2012) have calculated the N balance of the Hyytiälä SMEAR II Scots pine forest. The study shows that the forest ecosystem is a very efficient N recycler. Based on the new results, the atmospheric N deposition is much higher than previously estimated, and dry and wet organic deposition are important components of the total N input. However, although the pools, annual inputs, outputs and overall N cycling in the boreal forest have been resolved, new questions arise of the short-term dynamic N processes (such as amine formation via decomposition of soil organic nitrogen). These processes are important for the atmospheric chemistry and connect N even to climate effects of aerosols.

The N group at the Division of Atmospheric Sciences (Janne Korhonen, Antti-Jussi Kieloaho, and supervisors Mari Pihlatie and Jukka Pumpanen) are applying and developing new methods together with chemists, physicists and microbiologists. Current projects linking N and the atmosphere include studies on amine concentrations and fluxes, and the effect of fresh carbon input on soil organic nitrogen turnover (NITRGOFUNGI). In the future, our main focus in the nitrogen research will be to estimate reactive N emissions from soil and canopy, N transformations, and the fate of N deposited on to the forest canopy.

Contributors to the mind-map (working in the Division’s nitrogen group):

  • Jussi Heinonsalo (microbiology)
  • Maarit Raivonen (forest ecology)
  • Johanna Joensuu (forest ecology)
  • Timo Vesala (professor, micrometeorology)
  • Jukka Pumpanen (soil ecology)

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