Carbon and Nitrogen Interactions

We study the effect of nitrogen availability on carbon cycling processes and SOM accumulation in a long-term nitrogen addition experiment, in local nitrogen gradients (forest edges), in forest chronosequences and using national soil inventory data.

The long-term fate of the stable 15-N isotope is an important tool for understanding nitrogen (N) cycling and its potential effect on carbon (C) accumulation.

Most of the carbon and nitrogen stored in forest ecosystems is located in the soil bound together in soil organic matter (SOM).

The input of nitrogen via atmospheric deposition may thus enable the soil to sequester more carbon. On the other hand, the amount of available carbon in the soil may determine whether the nitrogen is retained or leached as nitrate. Despite these interactions, the cycling of these elements is often studied separately.

Our hypothesis is that N may increase the soil C-sink (through reduced decomposition) at N-limited conditions but as N availability increases the soil will become N-saturated (leaching nitrate) and the effect on the C-sink will fade and in some cases be negative.

Collaboration

The work is linked to international networks, such as Forest Soil Carbon-sink Nordic Network and CAR-ES.