Comparison of chilling and heat requirements for leaf unfolding in deciduous woody species in temperate and subtropical
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SPECIAL ISSUE: PHENOLOGY 2018
Comparison of chilling and heat requirements for leaf unfolding in deciduous woody species in temperate and subtropical China Yunjia Xu 1,2 & Junhu Dai 1,2
&
Quansheng Ge 1,2 & Huanjiong Wang 1 & Zexing Tao 1
Received: 1 July 2019 / Revised: 16 August 2020 / Accepted: 24 August 2020 # ISB 2020
Abstract Climate warming has advanced the spring phenology of many plant species by accelerating heat accumulation. However, delayed phenophases due to insufficient chilling have also been reported. Based on phenological observation data (1963–2010), we compared the effects of preseason chill and heat accumulation on leaf unfolding dates of four deciduous woody species (Lagerstroemia indica, Robinia pseudoacacia, Sophora japonica, and Ulmus pumila) in temperate and subtropical regions of China. Daily chill and heat accumulation were calculated by two chilling models (the Positive Utah Model and the Dynamic Model) and the Growing Degree Hour (GDH) Model. We determined the temporal trends in chill and heat accumulations for leaf unfolding of the four species. The results showed that there were shorter chilling periods in the subtropics than in temperate sites because the chilling period typically started later and ended earlier. There was no significant difference in the length of the forcing period in the different regions. The chilling requirements for leaf unfolding were higher in temperate regions (1344.9–1798.9 chilling units (CU) or 64.7–79.4 chilling portions (CP)) than in the subtropics (1145.9–1828.1 CU or 47.9–75.2 CP). Plants in the subtropics needed higher forcing temperatures (4135.8–10084.8 GDH) than those in temperate regions (3292.0–8383.6 GDH). The earlier-leafing species (e.g., U. pumila) had a lower heat requirement for leaf unfolding than the later-leafing species (e.g., L. indica). A significant increase in heat accumulation was found at all sites except Guiyang, while chill accumulation only increased in Beijing. Keywords Chilling and heat requirement . Climate change . Temperate zone . Subtropical zone . China
Introduction Phenology has provided substantial evidence of the impacts of climate change on the biosphere (Menzel et al. 2006; Peñuelas et al. 2013; Fu et al. 2015). Recent global warming has led to an overall earlier trend of plant spring phenology in the Northern Hemisphere (Parmesan and Yohe 2003; Root et al. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00484-020-02007-7) contains supplementary material, which is available to authorized users. * Junhu Dai [email protected] * Zexing Tao [email protected] 1
Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
2
University of Chinese Academy of Sciences, Beijing, China
2003; Richardson et al. 2013; Ge et al. 2015). However, the response of spring phenology to temperature is nonlinear (Chuine et al. 2010; Jochner et al. 2016). For most woody plan
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