樹木限界線の上昇がアルプスの湖に与える影響(How rising treelines can affect Alpine lakes)

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2024-05-08 スイス連邦工科大学ローザンヌ校(EPFL)

地球温暖化により樹木限界線が上昇し、高高度・高緯度の湖に近づいています。これが生態系に与える影響を調査するため、EPFLの科学者たちがフィンランドとオーストリアで研究を行いました。研究では、樹木限界線以下の土壌からの溶存有機物(DOM)が湖の細菌に与える影響を分析し、細菌がこのDOMにさらされると、バイオマスの生成が低下し、二酸化炭素(CO2)を多く放出することが判明しました。これにより、高高度・高緯度の湖で温室効果ガス排出が増加する可能性が示唆されています。今後さらなる研究が必要ですが、この現象は地球上の数千の湖に影響を及ぼす重要な発見となっています。

<関連情報>

樹木限界線の変位が高緯度・高度の湖沼の溶存有機物処理に影響する可能性 Treeline displacement may affect lake dissolved organic matter processing at high latitudes and altitudes

Núria Catalán,Carina Rofner,Charles Verpoorter,María Teresa Pérez,Thorsten Dittmar,Lars Tranvik,Ruben Sommaruga & Hannes Peter
Nature Communications  Published:26 March 2024
DOI:https://doi.org/10.1038/s41467-024-46789-5

樹木限界線の上昇がアルプスの湖に与える影響(How rising treelines can affect Alpine lakes)

Abstract

Climate change induced shifts in treeline position, both towards higher altitudes and latitudes induce changes in soil organic matter. Eventually, soil organic matter is transported to alpine and subarctic lakes with yet unknown consequences for dissolved organic matter (DOM) diversity and processing. Here, we experimentally investigate the consequences of treeline shifts by amending subarctic and temperate alpine lake water with soil-derived DOM from above and below the treeline. We use ultra-high resolution mass spectrometry (FT-ICR MS) to track molecular DOM diversity (i.e., chemodiversity), estimate DOM decay and measure bacterial growth efficiency. In both lakes, soil-derived DOM from below the treeline increases lake DOM chemodiversity mainly through the enrichment with polyphenolic and highly unsaturated compounds. These compositional changes are associated with reductions in bulk and compound-level DOM reactivity and reduced bacterial growth efficiency. Our results suggest that treeline advancement has the potential to enrich a large number of lake ecosystems with less biodegradable DOM, affecting bacterial community function and potentially altering the biogeochemical cycling of carbon in lakes at high latitudes and altitudes.

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