Controls on decomposition and soil nitrogen availability at high latitudes

At high latitudes, decomposition rates and soil nitrogen (N) availability are pivotal in determining ecosystem responses to climate change. The effects of temperature, soil moisture content, resource quality, and saprotrophic fungi as an example of soil organisms, on carbon (C) and N mineralisation are reviewed. The controls on N availability are less well characterised than those on decomposition, and C and net N mineralisation sometimes do not respond to these controls in a parallel manner. Increases in mean summer temperatures of 2-4degreesC predicted for high latitudes may not necessarily cause greater rates of decomposition and N mineralisation because of concomitant small rises in soil temperature together with interactions between the controls, including interactions of the temperature and moisture content of the substrata with the diversity and function of decomposer fungi. Research on decomposition and soil N availability has been carried out at several scales, at all of which future research remains necessary. It is not clear whether species diversity of decomposer fungi influences decomposition and C and N release above the microscale.