Understanding the responses of the date of autumn foliar senescence (DFS) to climate change is important for a better interpretation of carbon uptake.
The high northern latitudes (>50°) experienced a pronounced surface stilling (i.e., decline in winds) with climate change. But its influence on DFS remains unknown.
Prof. WU Chaoyang's team from the Institute of Geographic Sciences and Natural Resources Research (IGSNRR) of the Chinese Academy of Sciences found that decline in winds significantly extended DFS over high northern latitudes at a magnitude comparable with the temperature and precipitation effects.
Their findings were published in PNAS.
The researchers adopted 183,448 phenological observations at 2,405 sites, long-term site-scale water vapor and carbon dioxide flux measurements, and 34 y of satellite greenness data.
"We discovered that decline in winds reduces evapotranspiration, resulting in less soil water losses and consequently more favorable growth conditions in late autumn," said Prof. WU.
Declining winds also lead to less leaf abscission damage which could delay leaf senescence and to a decreased cooling effect and therefore less frost damage.
Since DFS is tightly connected with annual carbon uptake, an earlier DFS projected would cause a positive feedback to the climate.
Predicting how wind speeds respond to climate change remains challenging, but evidence suggests that wind speeds will be more extreme in several regions, although the mean annual speed continues to decrease.
