「光る 」植物はどのようにフラッシュ干ばつ予測に役立つか(How ‘Glowing’ Plants Could Help Scientists Predict Flash Drought)

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2024-05-14 NASA

NASAの研究によると、植物の生産性の急増が深刻な土壌水分の損失を予告することがあります。2012年夏に米国で発生した「フラッシュ干ばつ」は、急速に広がり30億ドル以上の経済損失をもたらしました。NASAのジェット推進研究所の科学者たちは、植物の光合成時に放出される微弱な光「太陽誘導蛍光(SIF)」を追跡し、フラッシュ干ばつの兆候を最大3ヶ月前に検出することに成功しました。この光はNASAの衛星OCO-2によって検出され、植物の成長とCO2吸収を示します。研究では、SIFデータと土壌水分データを比較し、干ばつ前に植物が異常に繁茂するパターンを確認しました。これにより、SIFがフラッシュ干ばつの早期警告指標として有望であることが示されました。

<関連情報>

瞬間的な干ばつ時の炭素損失を軽減する先行条件 Antecedent Conditions Mitigate Carbon Loss During Flash Drought Events

Nicholas Parazoo, Mahmoud Osman, Madeleine Pascolini-Campbell, Brendan Byrne
Geophysical Research Letters  Published: 24 April 2024
DOI:https://doi.org/10.1029/2024GL108310

「光る 」植物はどのようにフラッシュ干ばつ予測に役立つか(How ‘Glowing’ Plants Could Help Scientists Predict Flash Drought)

Abstract

Flash droughts– the rapid drying of land and intensification of drought conditions—have devasting impacts to natural resources, food supplies, and the economy. Less is currently known about the drivers of flash droughts and their impact on landscape carbon losses. We leverage carbon and water cycle data from NASA OCO-2 and Soil Moisture Active and Passive missions to quantify flash drought impacts on U.S. carbon exchange. On average, pre-onset carbon uptake fully offsets post-onset losses, creating a carbon neutral biosphere over a ±3 month period surrounding flash drought onset. This contrasts with ecosystem models, which underestimate pre-onset uptake and overestimate post-onset loss. Furthermore, spaceborne observations of solar induced fluorescence (SIF) provide a reliable indicator of flash droughts at lead times of 2–3 months, due to feedbacks between vegetation growth and soil water loss. This study is expected to improve understanding of flash drought impacts on carbon exchange, and facilitate flash drought early warning.

Key Points

  • Solar induced fluorescence offers early warning (∼2–3 months) for stealth drought events
  • Pre-drought carbon gains fully offset post-drought carbon loss
  • Terrestrial biosphere models overestimate total carbon loss

Plain Language Summary

Flash droughts have devasting impacts to the environment, natural resources, and society, and are difficult to predict. Here, we use NASA models and satellite observations to determine (a) the impact of flash drought on carbon exchange in land ecosystems, and (b) the extent to which satellite remote sensing can improve flash drought early warning. We find that beneficial environmental conditions occurring prior to onset of flash drought leads to increases in carbon uptake in ecosystems compared to normal conditions. This anomalous uptake of carbon in ecosystems is, on average, sufficient to fully offset inevitable decreases in carbon uptake associated with hot dry conditions following onset of flash drought, leading to a net zero impact of flash drought on carbon exchange over the 6-month period surrounding drought onset. Moreover, we find the satellite observations of solar induced chlorophyll fluorescence (SIF), representing a re-emission of radiation by plants following absorption of sunlight for growth, are extremely well correlated to soil moisture losses associated with flash drought at lead times of 6–12 weeks across diverse landscapes and ecoregions in North America. Satellite SIF thus shows promise as a reliable early warning indicator of flash drought, at sufficient lead time conducive to decision making.

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