- Conference Proceedings Paper
A number of observational studies indicate that the carbon uptake by terrestrial ecosystem and its response to changes in climate conditions depends on interaction between carbon and nitrogen dynamics. However, many of the terrestrial ecosystem models used for climate change study do not take this effect into account. We study the global impact of carbon/nitrogen interaction on the feedback between climate and a terrestrial carbon cycle by means of numerical simulations with Earth System model of intermediate complexity. Two versions of terrestrial ecosystem model (TEM), with (standard version) and without interaction between carbon and nitrogen cycles were used in this study. Feedback between the climate and terrestrial carbon cycle is examined by comparing results of Earth system model with various climate sensitivities to an increase in atmospheric CO2 concentration. Our results show that the interaction between terrestrial carbon and nitrogen changes both the sign and a magnitude of the feedback. In the simulations with the carbon only version of TEM, surface warming significantly reduces carbon uptake by both soil and vegetation leading to the positive carbon cycleclimate feedback. In contrast, if gross primary productivity is limited by nitrogen availability, climate change related increases in carbon uptake by vegetation exceeds an increase in soil carbon decomposition. As a result, the feedback between climate and terrestrial carbon uptake becomes negative, with the exception of very strong surface warming (in conjunction with high climate sensitivity) when terrestrial ecosystem becomes a carbon source. In spite of that, for small or moderate increase in surface temperature standard version of TEM takes less carbon than the carbon-only version, resulting in a larger increase in atmospheric CO2 concentration for a given global carbon emission.