In WY (2008/09), HNT had 24% and 6% more
stems, and HDNT had 45% and 14% (P > 0.05) more stems than CK
(P < 0.05) in the overwintering and reviving stages, respectively. In
CY (2009/10), HNT and HDNT both had significantly (P < 0.05) more
stems than CK at both stages. In AY (2010/11), HNT and HDNT
were not significantly different from CK at overwintering stage
(Fig. 5).
Overall, artificial warming caused an increase of the Active
Growth Period (without the overwintering) (AGP) for the three
growing seasons (Fig. 6a–c). In all three experimental years, the
beginning of the overwintering was delayed by an average of 6
days for the HNT and 7 days for HDNT, reviving date was advanced
by an average of 8 days for the HNT and 11 days for HDNT, and the
whole overwintering was shortened by an average of 14 days for
the HNT and 18 days for HDNT