Examining the Role of Climate, Carbon and Nitrogen Interactions in the Terrestrial Biosphere
Yang, Xiaojuan
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Permalink
https://hdl.handle.net/2142/85977
Description
Title
Examining the Role of Climate, Carbon and Nitrogen Interactions in the Terrestrial Biosphere
Author(s)
Yang, Xiaojuan
Issue Date
2009
Doctoral Committee Chair(s)
Atul Jain
Department of Study
Atmospheric Sciences
Discipline
Atmospheric Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biogeochemistry
Language
eng
Abstract
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.
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