世界陸地碳量計算 Constraining estimates of terrestrial carbon uptake
Figure 1
Schematic of the pathways by which CO2 fertilization effects (CFE) can increase gross primary productivity (GPP) and the potential ways satellite observations could be combined to constrain the CFE pathways. We define CFE pathways to include increases in light use efficiency (LUE), increases in water use efficiency (WUE), and increases in the fraction of photosynthetically active radiation (fAPAR). Satellite indices include leaf area index (LAI) and fAPAR, land surface temperature (LST), vegetation optical depth (VOD) and solar‐induced Chl fluorescence (SIF). We show different combinations of these satellite records and indicate their potential to globally constrain (green ticks), regionally constrain (yellow ticks) or fail to constrain (red crosses) a given CFE pathway. Regional constraints (yellow ticks) are most often limited by atmospheric effects and/or signal saturation in dense canopies, such as tropical forest ecosystems.
Figure 2
A timeline of satellite observations of leaf area index (LAI) and fraction of photosynthetically active radiation (fAPAR), land surface temperature (LST), vegetation optical depth (VOD) and solar‐induced fluorescence (SIF). Observation timelines are provided for context and are not meant to provide a comprehensive overview of all available sensors. This timeline clearly demonstrates the availability of diverse, multidecadal satellite observation records that are rapidly increasing in spatiotemporal resolution.
Figure 3
Global model‐derived and satellite‐derived carbon stock and flux estimates. Model outputs are from the Community Land Model (CLM 4.5 in CESM 1.2) and include above‐ground carbon (AGCCLM) for July 2007 (a), and gross primary productivity (GPPCLM) for July 2007 (b). Corresponding satellite‐derived estimates include AMSR‐E VOD‐derived above‐ground carbon (AGCVOD) for July 2007 (c), and GOME‐2 SIF for July 2007 (d).
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