Publication Date:
2019-11-02
Description:
Terrestrial ecosystems contribute most of the interannual variability (IAV) in atmospheric carbon dioxide (CO2) concentrations, but processes driving the IAV of net ecosystem CO2 exchange (NEE) remain elusive. For a predictive understanding of the global C cycle, it is imperative to identify indicators associated with ecological processes that determine the IAV of NEE. Here, we decompose the annual NEE of global terrestrial ecosystems into their phenological and physiological components, namely maximum carbon uptake (MCU) and release (MCR), the carbon uptake period (CUP), and two parameters, and , that describe the ratio between actual versus hypothetical maximum C sink and source, respectively. Using longterm observed NEE from 66 eddy covariance sites and global products derived from FLUXNET observations, we found that the IAV of NEE is determined predominately by MCU at the global scale, which explains 48% of the IAV of NEE on average while , CUP, , and MCR explain 14%, 25%, 2%, and 8%, respectively. These patterns differ in waterlimited ecosystems versus temperature and radiationlimited ecosystems; 31% of the IAV of NEE is determined by the IAV of CUP in waterlimited ecosystems, and 60% of the IAV of NEE is determined by the IAV of MCU in temperature and radiationlimited ecosystems. The LundPotsdamJena (LPJ) model and the Multiscale Synthesis and Terrestrial Model Intercomparison Project (MsTMIP) models underestimate the contribution of MCU to the IAV of NEE by about 18% on average, and overestimate the contribution of CUP by about 25%. This study provides a new perspective on the proximate causes of the IAV of NEE, which suggest that capturing the variability of MCU is critical for modeling the IAV of NEE across most of the global land surface.
Keywords:
Life Sciences (General)
Type:
GSFC-E-DAA-TN73315
,
Global Change Biology (ISSN 1354-1013) (e-ISSN 1365-2486); 25; 10; 3381-3394
Format:
application/pdf
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