The interaction between terrestrial carbon cycle and climate has received much attention due to the reason that the large quantities of carbon stored in living vegetation and soil organic matter and the release of this carbon could have serious impacts on climate. However, current coupled carbon cycle-climate models typically do not consider nitrogen dynamics and carbon-nitrogen-climate interactions, which could significantly change the terrestrial response to elevated CO2 and climate change. A geographically explicit process-based terrestrial nitrogen cycle model has been developed and coupled with the biogeochemical cycle component of an Integrated Science Assessment Model (ISAM) to study terrestrial carbon cycle, nitrogen cycle and climate in an integrated way. The model has been applied to a series of modeling experiments examining the influence of nitrogen cycling on the response of the terrestrial biosphere to elevated CO2, climate change, and nitrogen deposition. The results suggest that both the positive and negative feedback components of carbon-climate feedback are attenuated by the introduction of carbon-nitrogen-climate interactions; and anthropogenic nitrogen deposition leads to an important carbon sink in terrestrial biosphere.
In addition to changes of atmospheric CO2 and climate, terrestrial biosphere could also greatly influenced by anthropogenic disturbances, which include clearing of land for agriculture, conversion of forest to pasture, harvest of forest products, forest fires. In addition, changes in soil management can potentially increase the accumulation of soil organic carbon (SOC). I also examine the concurrent effects of increasing atmospheric CO2, climate change, nitrogen deposition, anthropogenic disturbances and soil management practices on terrestrial carbon cycling using the coupled ISAM modeling framework. This is the first attempt to consider the interactive effects of all major environmental factor changes on terrestrial biosphere on a global scale.