Abstract
Subtropical forests can sequester a larger amount of atmospheric carbon dioxide (CO2) relative to other terrestrial ecosystems through photosynthetic activity and act as an important role in mitigating global climate warming. Compared with the model-based gross primary production (GPP) products, satellite-derived solar-induced fluorescence (SIF) opens a new window for quantification. Here, we used the remotely sensed SIF retrievals, two satellite-driven GPP products including MODIS (GPPMOD) and BESS (GPPBESS), and tower-based GPP measurements at two contrasting subtropical forests to provide a systematic analysis. Our results revealed that GPP and the associated environmental factors exhibited distinct seasonal patterns. However, the peak GPP values had large differences, with stronger GPP in the evergreen needleleaf forest site (8.76 ± 0.71 g C m−2 d−1) than that in the evergreen broadleaf forest site (5.71 ± 0.31 g C m−2 d−1). The satellite-derived SIF retrievals showed great potential in quantifying the variability in GPP, especially for the evergreen needleleaf forest with r reaching up to 0.909 (p < 0.01). GPPMOD and GPPBESS showed distinctly different performances for the two subtropical forests, whereas the GPP estimates by exclusive use of satellite-based SIF data promised well to the tower-based GPP observations. Multi-year evaluation again confirmed the good performance of the SIF-based GPP estimates. These findings will provide an alternative framework for quantifying the magnitude of forest GPP and advance our understanding of the carbon sequestration capacity of subtropical forest ecosystems.
Highlights
The carbon sequestration potential of terrestrial forests is jointly affected by climate change and human-induced perturbation through land-use changes including deforestation and afforestation [9–11]
As the temperature rose in springtime (Figure 3), gross primary production (GPP) enhanced increasingly with the plant growth status, peaked in summertime, and decreased again in autumn
solar-induced fluorescence (SIF) seemed unable capture theg dramatic in less, this study found that GPPSIF seemed unable to capture the dramatic decline in the coniferous sitealso in summer
Summary
Licensee MDPI, Basel, Switzerland.Earth’s climate has changed dramatically in the past century and will keep changing during the few centuries. The IPPC AR6 report revealed that the global annual nearsurface temperature has been rising steadily from the latter part of the 19th century and places the year 2020 as one of the three warmest years on record [1]. The carbon sequestration potential of terrestrial forests is jointly affected by climate change and human-induced perturbation through land-use changes including deforestation and afforestation [9–11]. It is imperative to accurately evaluate the dynamics of terrestrial forest carbon cycles in order to predict the feedback on Earth’s climate system
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