The international
researchers investigated the change in the sensitivity of leaf unfolding
to climate warming
using observations for dominant European tree species like this beech.
(Photo: Stefanie
Ederer)
The response of leaf unfolding phenology to climate warming
has significantly reduced
(September 29, 2015) The
sensitivity of leaf unfolding phenology to climate warming has significantly
declined since 1980s, according to a study recently published in the journal
Nature by an international collaboration of scientists. Earlier spring leaf
unfolding is a frequently observed response of plants to climate warming. Many
deciduous tree species require cold temperatures, in other words ‘chilling’,
for dormancy release, and the warming-related reductions in chilling may
counteract the advance of leaf unfolding in response to warming. Empirical
evidence for this, however, was very limited.
To check whether warm winters have already attenuated the
advance in spring phenology, an international team of researchers from China,
Belgium, France, Spain, Switzerland and Germany investigated the change in the
sensitivity of leaf unfolding to climate warming using long-term observations
for seven dominant European tree species at 1245 sites in Central Europe.
Their analyses show that leaf unfolding occurred, on
average, four days earlier per degree Celcius increase in spring temperature
between 1980 and 1994, whereas this advance dropped to 2.3 days per degree
between 1999 and 2013, a decrease of over 40 percent. “This lower sensitivity
of trees to climate change likely reflects the reduced cold during winter that
delays dormancy release. However, we could not fully exclude photoperiod and/or
insolation as co-controlling mechanisms. These two factors may also become
limiting when leaf unfolding dates occur too early in spring” said Yongshuo H.
Fu, the first author of this study.