Sensitivity of large-scale vegetation greenup and dormancy dates to climate change in the north−south transect of eastern China

Phenology event responses, based on vegetation types, are strong indicators of climate variability and the ability of the vegetation to adapt to future climate changes. However, the sensitivity of phenology events to climate change along either environmental or vegetation type gradients is rarely examined. Phenological curves of major vegetation types along the North−South Transect of Eastern China (NSTEC) have been developed using wavelet and smooth-spline methods based on the normalized difference vegetation index from 1982 to 2006. Spatial−temporal patterns, trends of greenup-onset dates, dormancy dates, and growing season lengths (GSLs) during the period of 1982−2006 are presented. The greenup-onset dates were most significantly and negatively related to the temperature in cold and humid areas, but insignificantly and positively in semi-arid regions. However, dormancy date showed a positive correlation with temperature. In populations of the same vegetation type, distributed along thermal gradients of NSTEC, the phenology sensitivities to warming were different. Greenup sensitivities of cold temperate coniferous forest (CTCF) and temperate meadow steppe (TMS) increased significantly from −6.0 to 0 days °C−1 (p < 0.001) and from about −2.0 to 2.0 days °C−1 (p < 0.001), respectively. In contrast, temperate grass steppe (TGS) and temperate deciduous shrubland (TDS) showed a decreased trend of greenup sensitivity from 2.0 to −4.0 days °C−1 (p < 0.001) and from 2.0 to −6.0 days °C−1 (p < 0.001), respectively. For the dormancy date sensitivity, CTCF showed a decreasing trend from about 6.0 to 0 days °C−1 (p < 0.001), and subtropical evergreen-broadleaved forest (SEBF) decreased from 5.0 to −5.0 days °C−1 (p < 0.05). Acknowledgements This research was jointly supported by the National Natural Science Foundation of China (No. 31290223), Special Research Programme for Public-welfare Forestry (Nos. 200804001 and 201104006), National Science and Technology Support Programme (No. 2012BAD22B01), Chinese Academy of Forestry Foundation (CAFYBB2008007), and Key Laboratory of Forest Ecology and Environment of State Forestry Administration. We gratefully acknowledge two anonymous reviewers for their constructive comments for improvement of the article.