As extreme droughts become more frequent and severe, forests worldwide are dying at alarming rates. However, it remains poorly understood how tree species’ physiological strategies interact with local microenvironments to shape landscape-scale dieback patterns.

In a study published in Forest Ecology and Management, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences have uncovered how two dominant pine species in Southwest China responded to the extreme drought of 2023. Their findings reveal that forest dieback is not a uniform phenomenon but shaped by species-specific vulnerabilities and local environmental conditions.

The study was conducted across 20 large forest plots (4 hectares each) in Yunnan Province, a biodiversity hot spot that experienced an unprecedented eight-month drought between 2022 and 2023.

The researchers integrated drone surveys, high-resolution satellite imagery, and environmental data to investigate a widespread dieback event affecting Pinus yunnanensis (Yunnan pine) and Pinus kesiya var. langbianensis (Simao pine). They systematically assessed post-drought canopy mortality dynamics, water response trajectories, and recovery capacity of the two pine species. They also quantified the key drivers behind the spatial patterns of dieback.

The results showed that the 2023 drought caused a sharp drop in the Normalized Difference Water Index (NDWI) for both species. However, their post-drought recovery paths diverged significantly. Areas of Yunnan pine dieback exhibited irreversible damage, with no meaningful recovery. By contrast, Simao pine showed rapid but incomplete recovery, suggesting a persistent drought legacy effect.

Further analysis identified distinct constraints driving dieback in each species. For Yunnan pine, dieback was primarily driven by intrinsic stand traits, including tree age, canopy height, and soil potassium levels. Older stands and those with nutrient imbalances were far more likely to collapse. For Simao pine, the dominant factor was topography, especially slope aspect and steepness. Southfacing slopes, which receive more solar radiation and experience greater water loss, were disproportionately affected.

The study generated spatially explicit risk maps, revealing that dieback hotspots are disproportionately located near the distributional margins of both species. The populations living at the edge of their physiological limits are most vulnerable to climatedriven extremes.

“Our results provide new mechanistic insight into species-specific drought vulnerability. Effective adaptation strategies must move beyond generalized assessments toward species- and site-specific interventions. It is necessary to integrate multi-scale observations, such as unmanned aerial vehicle (UAV) and satellite data, to improve the accuracy of forest mortality predictions,” said FAN Zexin of XTBG.

Forest of Pinus kesiya var. langbianensis (Simao pine) after drought. (Image by GAO Daoxiong)

Forest of Pinus yunnanensis (Yunnan pine) after drought. (Image by GAO Daoxiong)

Available online: 13 May 2026