2025-07-17 パシフィック・ノースウェスト国立研究所 (PNNL)
PNNLらの研究チームは、海面上昇による海水曝露が沿岸針葉樹林の枯死に与える影響を、動的植生モデルFATES-Hydroを用いて3地点で解析した。急激な海水曝露では土壌塩分と低酸素が急増し、光合成能力や根のバイオマスが急激に低下、炭素飢餓と水輸送機能の喪失（ハイドロリックフェイル）が同時に発生し、速やかに枯死する。一方、緩やかな海水曝露では水輸送障害が先行し、時間をかけて炭素飢餓が加わる。これにより、枯死の速度や要因は曝露速度により異なると判明した。本研究は「ゴーストフォレスト」の予測や気候変動対策に有用である。
＜関連情報＞
- https://www.pnnl.gov/publications/revealing-underlying-mechanisms-seawater-driven-coastal-conifer-mortality
- https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.19076
海水暴露下における針葉樹の枯死メカニズムのモデル化 Modeling the mechanisms of conifer mortality under seawater exposure
Junyan Ding, Nate McDowell, Yilin Fang, Nicholas Ward, Matthew L. Kirwan, Peter Regier, Patrick Megonigal, Peipei Zhang, Hongxia Zhang, Wenzhi Wang, Weibin Li …
New Phytologist Published: 27 June 2023
DOI:https://doi.org/10.1111/nph.19076
Summary
- Relative sea level rise (SLR) increasingly impacts coastal ecosystems through the formation of ghost forests. To predict the future of coastal ecosystems under SLR and changing climate, it is important to understand the physiological mechanisms underlying coastal tree mortality and to integrate this knowledge into dynamic vegetation models.
- We incorporate the physiological effect of salinity and hypoxia in a dynamic vegetation model in the Earth system land model, and used the model to investigate the mechanisms of mortality of conifer forests on the west and east coast sites of USA, where trees experience different form of sea water exposure.
- Simulations suggest similar physiological mechanisms can result in different mortality patterns. At the east coast site that experienced severe increases in seawater exposure, trees loose photosynthetic capacity and roots rapidly, and both storage carbon and hydraulic conductance decrease significantly within a year. Over time, further consumption of storage carbon that leads to carbon starvation dominates mortality. At the west coast site that gradually exposed to seawater through SLR, hydraulic failure dominates mortality because root loss impacts on conductance are greater than the degree of storage carbon depletion.
- Measurements and modeling focused on understanding the physiological mechanisms of mortality is critical to reducing predictive uncertainty.
