H33I-0953:
From roots to globe: How the terrestrial nitrogen cycle alters the global carbon cycle?
Wednesday, 17 December 2014
Mingjie Shi, University of California, Los Angeles, JIFRESSE, Los Angeles, CA, United States, Joshua B Fisher, NASA Jet Propulsion Laboratory, Pasadena, CA, United States, Edward R Brzostek, Indiana University Bloomington, Department of Biology, Bloomington, IN, United States and Richard Phillips, Indiana University, Bloomington, IN, United States
Abstract:
Plants typically expend a significant portion of their available carbon for nitrogen (N) acquisition, especially through root exudation in N-limited soils; this is the amount of carbon that would otherwise go to growth in the presence of ample N. Most global terrestrial biogeochemistry models (TBMs) do not consider the carbon cost for N acquisition. In order to evaluate the carbon–nitrogen trade process and improve the carbon–nitrogen dynamics in TBMs, this study integrates a cutting-edge global plant nitrogen model—Fixation and Uptake of Nitrogen (FUN) version 2.0 (FUN2.0) into the Community Land Model 4.0. The coupled model (i.e., CLM4CN-FUN2.0) is tested at local and global scales. Generally, plant N acquisition is dynamically simulated, and the carbon cost for N acquisition is estimated by the coupled model. Sensitivity tests indicate that the low soil N uptakes of the coupled model are associated with the low soil mineral N amount represented by CLM4CN. According to the observational evidence, the retranslocated N pool in CLM4CN needs to be combined with other non-structural N pools. These deficiencies in the model open new possibilities for improving TBMs, which is widely used in global climate change studies.
