「喉が渇いた」樹木が森林を気候変動に対してより脆弱にする可能性(How “thirsty” trees may make forests more vulnerable to climate change)

2024-12-11 ノースカロライナ州立大学(NCState)

ノースカロライナ州立大学の研究によると、カエデなどの「拡散多孔質」樹種は、オークなどの「環状多孔質」樹種に比べて多くの水を必要とします。気候変動により乾燥期間が増加する中、これらの水を多く消費する樹種が増加すると、降雨時に森林がより多くの水を吸収し、河川への流出量が減少します。その結果、干ばつの影響が増大し、森林の炭素隔離能力も低下する可能性があります。研究チームは、将来の乾燥および多雨のシナリオをモデル化し、拡散多孔質樹種の増加が水の損失と河川流量の減少を引き起こすことを確認しました。従来のモデルは樹種間の水利用差を考慮しておらず、この点が脆弱性の過小評価につながっていた可能性があります。

＜関連情報＞

気候変動と種の相互作用が将来の森林の炭素と水のバランスを左右する Interactions Between Climate and Species Drive Future Forest Carbon and Water Balances

Katie A. McQuillan, A. Christopher Oishi, Zachary J. Robbins, Robert Scheller, Katherine L. Martin
Ecohydrology Published: 04 December 2024
DOI:https://doi.org/10.1002/eco.2748

ABSTRACT

Global change is altering forest carbon and water balances; however, the extent to which tree species shape ecosystem-scale responses to climate, particularly in biodiverse forests, remains unclear. To address this, we simulated the effects of an envelope of future climate conditions on watershed carbon and water balances and quantified the contributions of tree species based on their xylem anatomy. We accomplished this by incorporating species-level transpiration calculations into a landscape-scale ecosystem process model. Our revised model linked the effects of forest succession, species composition, and climate change on water and carbon. Calibration of forest water fluxes using sap flux measurements and catchment water balances captured variability in species transpiration and interannual ET in biodiverse, humid temperate forest catchments in the southern Blue Ridge Mountains, USA. Across wet and dry future climate projections, ET increased, and streamflow and net carbon uptake decreased, particularly under a scenario of increasing drought. Despite accounting for just 30% of current biomass, diffuse-porous tree species were the main driver of carbon and water flux responses now and in the future, thus intensifying the increase in ET and decline in streamflow. As diffuse-porous biomass continues to increase, these forests will be increasingly sensitive to drought, amplifying losses of carbon sequestration and freshwater delivery.