2026-06-23 中国科学院（CAS）
＜関連情報＞
- https://english.cas.cn/newsroom/research-news/202606/t20260623_1174507.shtml
- https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025JG009426
諸刃の剣：熱帯林における樹冠照明は、大木の干ばつに対する脆弱性を増幅させる A Double-Edged Sword: Crown Illumination Amplifies the Drought Vulnerability of Large Trees in a Tropical Forest
Zheng-Hong Tan, Yuan Li, Min Cao, Jie Yang, Hua-Zheng Lu, Yun Deng, Wen-Fu Zhang, Jin-Long Dong, Yue-Hua Hu, Lu-Xiang Lin
Journal of Geophysical Research: Biosciences Published: 12 May 2026
DOI:https://doi.org/10.1029/2025JG009426
Abstract
Tropical droughts are becoming more frequent and intense, which has raised concerns about their impact on tropical forests. However, the specific impacts of drought on these forests and the underlying response mechanisms remain poorly understood. Understanding these dynamics is critical, as tropical forests are vital for maintaining high biodiversity, storing large amounts of biomass, and sustaining high rates of carbon assimilation. To investigate the response of a tropical rainforest to severe drought, we analyzed a comprehensive 12-year data set of continuous dendrometer recordings from over 2,700 trees. Data showed that biomass increment was significantly inhibited during the drought period. Interestingly, multidimensional analyses based on 10 key functional traits revealed limited explanatory power for both drought and recovery effects, suggesting that intrinsic functional signals might be largely masked by high environmental heterogeneity. Furthermore, the linear mixed model identified that crown illumination, tree size and season—specifically their three-way interaction—as the dominant drivers of the drought effect (conditional R2 = 0.674). Conversely, competition index and habitat type showed relatively limited effects. Our results indicate that the widely observed vulnerability of large trees is not a simple function of tree size but an interactive response mediated by crown illumination and seasonal dynamics. We propose that the photosynthetic benefits of high light acquisition in large trees are likely counterbalanced by the amplified atmospheric stress and hydraulic risk during drought. These findings emphasize the importance of incorporating individual-level microclimate data to gain a comprehensive understanding of tropical forest resilience in a heterogeneous environment.
Plain Language Summary
Tropical droughts are becoming more frequent, yet we still do not fully understand why some trees are more vulnerable than others. Using 12 years of growth measurements from more than 2,700 trees in a tropical rainforest, we found that large trees were not simply more vulnerable because of their size; their drought response also depended on crown light exposure and season. While high light can promote tree growth under favorable conditions, it can also increase drought stress, especially for larger trees. These results highlight the importance of the local light environment in understanding tropical forest resilience under climate change.
