Effects of Nitrogen Availability, Climate, and Land-Use Change on Future Terrestrial Carbon Sink

Abstract:

Decreasing atmospheric CO2 concentrations by increasing the terrestrial carbon sink is one possible option to reduce man made climate change. Terrestrial CO2 uptake can be increased by large scale afforestation as projected in the RCP4.5 scenario. In addition, future CO2 fertilization will lead to an enhanced CO2 uptake by plants. The strength of the terrestrial CO2 sink depends on both the uptake of CO2 by plants and the release of CO2 during soil respiration. Both factors are influenced by climatic conditions and availability of nutrients such as nitrogen. Availability of nitrogen in the soil depends on the amount of nitrogen released during mineralization and the amount of nitrogen lost e.g. through leaching or gaseous emissions. As those processes are sensitive to climatic conditions, availability if nitrogen will be affected by future climate change. This study examines the effect of nitrogen availability on the terrestrial CO2 sink under future climate and the RCP land use by applying the land component of the MPI Earth system model. A combination of different land use and climate forcings allows for a quantification of important factors influencing the interactions between climate, nitrogen and land use.