Examining the Role of Climate, Carbon and Nitrogen Interactions in the Terrestrial Biosphere

In the second part of this thesis, a comprehensive model of terrestrial nitrogen (N) dynamics is developed and coupled with the geographically explicit terrestrial C cycle model of ISAM. Observations from the Long-term Intersite Decomposition Experiment (LIDET) dataset were compiled for the calibration and validation of the decomposition submodel. The terrestrial C-N cycle model was then used to evaluate how the introduction of N dynamics and interactions between C, N and climate influences terrestrial C sources and sinks in response to changes over the 20th century in global environmental factors including atmospheric CO2 concentrations, N deposition, climate and land use. This study shows (i) The terrestrial C sink from CO2 fertilization effect is reduced due to the limitation of N (by 0.53GtC/yr in the 1990s), (ii) the positive feedback between climate warming and terrestrial C cycle is attenuated due to the interactions between C, N and climate (by 0.34 GtC/yr in the 1990s), (iii) an enhanced terrestrial sink associated with N deposition (of 0.26 GtC/yr in the 1990s) and (iv) an enhanced source associated with changes in land use due to N limitation (of 0.08 GtC/yr in the 1990s). This study also suggests that the C sink associated with increasing atmospheric CO2 in subtropics is overestimated and the C source associated with changes in temperature and precipitation in higher latitude regions is underestimated when terrestrial N dynamics are not considered. This study highlights the importance of including the N dynamics when assessing terrestrial C sources and sinks with coupled C-climate system models.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Atmospheric Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Yang, Xiaojuan

Contributors dc:contributor

• Atul Jain

• Biogeochemistry

Language dc:language

eng

Identifier

(MiAaPQ)AAI3363120

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/85977