Forests play a crucial role in the global water cycle. Only a few studies have investigated post-damage radiative forcing of evapotranspiration and its underlying processes in forests. In 2015，a heavy snowfall happened in Ailaosahn subtropical forest in southwest China and has resulted in significant damage to the vegetation. However, the resilience of evapotranspiration (ET) and its partitioning in the forest to such events remains highly uncertain.
In a study published in Journal of Hydrology: Regional Studies, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) investigated the water flux recovery of the forest in the Ailao Mountain National Nature Reserve, a mountainous water catchment area for the Lancang River basin and a subtropical ecological conservation area in SW China, after an extreme snow disaster. They focused on how the water fluxes of subtropical forests responded to extreme weather disturbances and the recovery process over several years after a disaster.
By using eddy covariance data from 2010 to 2019, the researchers assessed the impact of extreme snow disasters on forest water fluxes and their subsequent recovery processes. They quantified the impact of the disasters on the forest water cycle and tracked the recovery dynamics by comparing changes in parameters such as evapotranspiration (ET), transpiration (T), evaporation (E), and canopy conductance (Gc) before and after an extreme snow disaster event in Ailaoshan subtropical forest.
The results showed asynchronous responses of different water flux processes, evaporation and transpiration, to an extreme snow event during the post-damage period in an old-growth subtropical forest in Ailao Mountains.
It was found that the leaf area index (LAI) decreased by 49% compared with the pre-disaster level in the snow disaster year. Severe vegetation damage led to decreases in evapotranspiration (ET), transpiration (T), evaporation (E), and canopy conductance (Gc) by 35%, 36%, 23%, and 33%, respectively, compared with the pre-disaster levels. Transpiration recovered rapidly in 2016 due to understory vegetation growth, while evaporation and canopy conductance recovered only until 2018. The reduced ET resulted in a strong positive radiative forcing of evapotranspiration, which reduced the forest's evaporative cooling and resilience.
The results suggested that delayed evaporation recovery in subtropical forests helped water storage in the ecosystem to support rapid growth of understory vegetation through transpiration, thus enhancing ecosystem resilience to disturbance.
“Our finding has important implications for understanding the adaptive capacity and stability of forest ecosystems when facing future climate change challenges,” said SONG Qinghai of XTBG.
Contact
SONG Qinghai Ph.D Principal Investigator
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
E-mail: sqh@xtbg.ac.cn
Published: 4 September 2024
