Journal Article

Topography constrains the climatic response of treeline migration in Taiwan's subalpine forests

Chen, Kuan‐Yu, Peereman, Jonathan, Hogan, J. Aaron, Lin, Teng‐Chiu

2026

Overview

Treelines are moving upslope, but the rates and drivers differ among different regions, globally. Many studies have examined the relationship between treeline movement and climate change, particularly rising temperature, while the role of topographical factors has received much less attention, despite the longstanding recognition of its importance. We examined treeline dynamics from 1980 to 2021 in two mountain ranges of Taiwan, the Yushan Mountain Range (YMR) and the Central Mountain Range (CMR), in relation to topography and climate using multi‐temporal aerial imagery and U‐Net deep‐learning segmentation. Treeline elevation advanced approximately 60 m on the two mountains and was accompanied by forest area expansion of 197 ha in the YMR and 158 ha in the CMR, which was mainly due to upward forest movement, not tree densification. Elevation, increases in growing‐season temperature and minimum temperature, and growing‐season precipitation were important predictors of forest area expansion. In contrast, elevation, increases in growing‐season precipitation and maximum temperature, and slope steepness were key predictors of treeline movement. Treeline upslope migration was approximately two times greater during the 1980–2001 period (2.1 in the YMR and 1.6 m year−1 in the CMR) compared to the 2001–2021 period (1.0 in the YMR and 0.75 m year−1 in the CMR), likely because forests already occupied most of the suitable habitat, and topographic factors constrained upward movement. Our study highlights the importance of accounting for both climatic and topographic factors in understanding treeline responses to climate change. In addition, our results indicate that treeline advance in mountain island forests, such as those in Taiwan, may be approaching an elevational limit, above which further upward migration is likely to exhibit a more muted response to further warming.

• Publisher: Wiley
• Subject: Environmental sciences & ecology / Life sciences / Sciences de l’environnement & écologie / Sciences du vivant