China's planted forests are more vulnerable to flash droughts, study finds
SciOpen
image:
The analysis identified and characterized flash and slow droughts in natural and planted forests. A Bi-GRU network simulated baseline monthly drought days (MPDD), while a KNN algorithm matched forest stands by environmental covariates to ensure comparable climates. Using these matched pairs, counterfactual scenarios isolated how forest type affects drought regulation, holding climate constant. Finally, SHAP analysis identified key drought risk drivers for each forest type.
view moreCredit: Kai Duan, School of Civil Engineering, Sun Yat-Sen University, Guangzhou, China
China has planted more than 77 million hectares (around 770,000 km²) of forests over the past several decades as part of the world's largest reforestation program. The effort has helped restore degraded landscapes, store carbon, and expand forest cover. But new research suggests that planted forests respond to drought differently from natural forests. The research finding was published in Forest Ecosystems.
Using satellite observations spanning 1990 to 2024, researchers from Sun Yat-Sen University investigated how planted and natural forests across China respond to two distinct types of drought: rapid-onset "flash droughts" and longer-lasting "slow droughts."
The results reveal a clear trade-off. Planted forests experienced more frequent flash droughts than natural forests, averaging 7.05 events every five years compared with 5.76 in natural forests. In contrast, natural forests experienced more slow droughts, averaging 3.77 events compared with 3.25 in planted forests.
Even after accounting for differences in climate, the researchers found that forest characteristics themselves influenced drought risk. Compared with similar natural forests, planted forests showed a 7% higher risk of flash drought but a 12% lower risk of slow drought.
The contrasting responses appear to be linked to differences in forest structure. Natural forests typically contain a greater variety of tree species, trees of different ages, and more complex canopy layers. Older trees often have deeper root systems that can access water stored deeper in the soil, helping forests withstand sudden moisture shortages.
Planted forests, by contrast, are often younger and less diverse, with simpler structures and shallower roots. These characteristics make them more vulnerable when moisture levels decline rapidly during heatwaves or other extreme weather events. At the same time, their lower overall biomass and water demand may help reduce vulnerability to prolonged drought.
The differences were most pronounced in China's mid-temperate semi-humid regions and on the Tibetan Plateau, where large areas have been converted to planted forests.
Increasing forest area alone may not be enough to ensure long-term resilience. Instead, the study highlights the importance of forest composition and structure. Management strategies that promote mixed-species forests, greater structural diversity, and more natural forest characteristics could help reduce vulnerability to rapid drought events.
Moreover, unrestricted expansion of plantations in water-limited regions should also be cautioned against. Although planted forests generally experienced fewer slow droughts, their recovery was more protracted and challenging.
DOI Link:
https://doi.org/10.1016/j.fecs.2026.100462
Journal
Forest Ecosystems
Article Title
Understanding flash drought variations in China's planted and natural forests through machine learning counterfactual analysis
No comments:
Post a Comment