Melinda Firds Program Management Unit Assistant
World Agroforestry (ICRAF)
Jl. CIFOR, Situ Gede, Sindang Barang,
Bogor Barat - Indonesia 16115
Tel: +62 2511 8625415
Fax: +62 2511 8625416
Email: icrafseapub@cgiar.org
Chilling requirement, Climate change, Flowering, Fruit trees, Heat requirement, Partial least squares regression
Abstract:
Climate change has affected the rates of chilling
and heat accumulation, which are vital for flowering and
production, in temperate fruit trees, but few studies have been
conducted in the cold-winter climates of East Asia. To evaluate
tree responses to variation in chill and heat accumulation
rates, partial least squares regression was used to correlate first
flowering dates of chestnut (Castanea mollissima Blume) and
jujube (Zizyphus jujube Mill.) in Beijing, China, with daily
chill and heat accumulation between 1963 and 2008. The
Dynamic Model and the Growing Degree Hour Model were
used to convert daily records of minimum and maximum
temperature into horticulturally meaningful metrics. Regression
analyses identified the chilling and forcing periods for
chestnut and jujube. The forcing periods started when half the
chilling requirements were fulfilled. Over the past 50 years,
heat accumulation during tree dormancy increased significantly,
while chill accumulation remained relatively stable for both
species. Heat accumulation was the main driver of bloom
timing, with effects of variation in chill accumulation
negligible in Beijing’s cold-winter climate. It does not seem
likely that reductions in chill will have a major effect on the
studied species in Beijing in the near future. Such problems
are much more likely for trees grown in locations that are
substantially warmer than their native habitats, such as temperate
species in the subtropics and tropics.
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