Widespread reduction in sun-induced fluorescence from the Amazon during the 2015/2016 El Niño

Koren, Gerbrand; Schaik, Erik van; Araùjo, Alessandro; Boersma, K. F.; Gärtner, Antje; Killaars, Lars; Kooreman, Maurits L.; Kruijt, B.; Laan-Luijkx, Ingrid T. van der; Randow, Celso von; Smith, Naomi; Peters, Wouter

doi:10.1098/rstb.2017.0408

Cited by 69 publications

(86 citation statements)

References 51 publications

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“…Their striking consistency holds under both normal and stressed conditions. In particular, the decrease of SIF oco2_orbit during peak drought in November 2015 (Koren et al, 2018) was successfully captured by SIF oco2_005 (Figure S8b). In particular, the decrease of SIF oco2_orbit during peak drought in November 2015 (Koren et al, 2018) was successfully captured by SIF oco2_005 (Figure S8b).…”

Section: Spatial and Temporal Patterns Of Sif Oco2_005mentioning

confidence: 81%

High‐Resolution Global Contiguous SIF of OCO‐2

Wen

Chang

et al. 2019

Geophysical Research Letters

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The Orbiting Carbon Observatory‐2 (OCO‐2) collects solar‐induced chlorophyll fluorescence (SIF) at high spatial resolution along orbits ( trueSIF¯oco2_orbit), but its discontinuous spatial coverage precludes its full potential for understanding the mechanistic SIF‐photosynthesis relationship. This study developed a spatially contiguous global OCO‐2 SIF product at 0.05° and 16‐day resolutions ( trueSIF¯oco2_005) using machine learning constrained by physiological understandings. This was achieved by stratifying biomes and times for training and predictions, which accounts for varying plant physiological properties in space and time. trueSIF¯oco2_005 accurately preserved the spatiotemporal variations of trueSIF¯oco2_orbit across the globe. Validation of trueSIF¯oco2_005 with Chlorophyll Fluorescence Imaging Spectrometer airborne measurements revealed striking consistency (R2 = 0.72; regression slope = 0.96). Further, without time and biome stratification, (1) trueSIF¯oco2_005 of croplands, deciduous temperate, and needleleaf forests would be underestimated during the peak season, (2) trueSIF¯oco2_005 of needleleaf forests would be overestimated during autumn, and (3) the capability of trueSIF¯oco2_005 to detect drought would be diminished.

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Section: Spatial and Temporal Patterns Of Sif Oco2_005mentioning

confidence: 81%

High‐Resolution Global Contiguous SIF of OCO‐2

Wen

Chang

et al. 2019

Geophysical Research Letters

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“…Field experiments at the Amazon KM83 site convinced that strong radiation resulted in increased leaf temperature, which reduced canopy photosynthesis [60]. Koren et al [62] applied SIF to quantify the impact of the 2015/2016 El Niño drought in Amazon and found that SIF was strongly inhibited over areas with anomalously decreased soil moisture and high temperatures.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Widespread Decline in Vegetation Photosynthesis in Southeast Asia Due to the Prolonged Drought During the 2015/2016 El Niño

2019

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El Niño events are known to be associated with climate extremes and have substantial impacts on the global carbon cycle. The drought induced by strong El Niño event occurred in the tropics during 2015 and 2016. However, it is still unclear to what extent the drought could affect photosynthetic activities of crop and forest in Southeast Asia. Here, we used the satellite solar-induced chlorophyll fluorescence (SIF), which is a proxy of actual photosynthesis, along with traditional vegetation indices (Enhanced Vegetation Index, EVI) and total water storage to investigate the impacts of El Niño–induced droughts on vegetation productivity of the forest and crop in the Southeast Asia. We found that SIF was more sensitive to the water stress than traditional vegetation indices (EVI) to monitor drought for both evergreen broadleaf forest and croplands in Southeast Asia. The higher solar radiation partly offset the negative effects of droughts on the vegetation productivity, leading to a larger decrease of SIF yield (SIFyield) than SIF. Therefore, SIFyield had a larger reduction and was more sensitive to precipitation deficit than SIF during the drought. The comparisons of retrieved column-average dry-air mole fraction of atmospheric carbon dioxide with SIF demonstrated the reduction of CO2 uptake by vegetation in Southeast Asia during the drought. This study highlights that SIF is more beneficial than EVI to be an indicator to characterize and monitor the dynamics of drought in tropical vegetated regions.

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“…For the 2005 and 2010 droughts, C emissions from the Amazon rainforest were estimated to bẽ 1.6 Pg C and~2.2 Pg C, respectively [5]. During the period from September 2015 to March 2016, the terrestrial water storage in the Amazon basin was lower by one standard deviation (sd) than the 1900-2016 climatological seasonal cycle, and in August 2016, the rainfall remained 10% below the average values, leading to strong reductions in gross primary productivity (GPP; [7]). Such repeated drought events have the potential to turn the forest into a C source [5,8].…”

Section: Introductionmentioning

confidence: 99%

OCO-2 Solar-Induced Chlorophyll Fluorescence Variability across Ecoregions of the Amazon Basin and the Extreme Drought Effects of El Niño (2015–2016)

et al. 2020

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Amazonian ecosystems are major biodiversity hotspots and carbon sinks that may lose species to extinction and become carbon sources due to extreme dry or warm conditions. We investigated the seasonal patterns of high-resolution solar-induced chlorophyll fluorescence (SIF) measured by the satellite Orbiting Carbon Observatory-2 (OCO-2) across the Amazonian ecoregions to assess the area´s phenology and extreme drought vulnerability. SIF is an indicator of the photosynthetic activity of chlorophyll molecules and is assumed to be directly related to gross primary production (GPP). We analyzed SIF variability in the Amazon basin during the period between September 2014 and December 2018. In particular, we focused on the SIF drought response under the extreme drought period during the strong El Niño in 2015–2016, as well as the 6-month drought peak period. During the drought´s peak months, the SIF decreased and increased with different intensities across the ecoregions of the Amazonian moist broadleaf forest (MBF) biome. Under a high temperature, a high vapor pressure deficit, and extreme drought conditions, the SIF presented differences from −31.1% to +17.6%. Such chlorophyll activity variations have been observed in plant-level measurements of active fluorescence in plants undergoing physiological responses to water or heat stress. Thus, it is plausible that the SIF variations in the ecoregions’ ecosystems occurred as a result of water and heat stress, and arguably because of drought-driven vegetation mortality and collateral effects in their species composition and community structures. The SIF responses to drought at the ecoregional scale indicate that there are different levels of resilience to drought across MBF ecosystems that the currently used climate- and biome-region scales do not capture. Finally, we identified monthly SIF values of 32 ecoregions, including non-MBF biomes, which may give the first insights into the photosynthetic activity dynamics of Amazonian ecoregions.

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Widespread reduction in sun-induced fluorescence from the Amazon during the 2015/2016 El Niño

Cited by 69 publications

References 51 publications

High‐Resolution Global Contiguous SIF of OCO‐2

High‐Resolution Global Contiguous SIF of OCO‐2

Widespread Decline in Vegetation Photosynthesis in Southeast Asia Due to the Prolonged Drought During the 2015/2016 El Niño

OCO-2 Solar-Induced Chlorophyll Fluorescence Variability across Ecoregions of the Amazon Basin and the Extreme Drought Effects of El Niño (2015–2016)

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