Leaf onset in the northern hemisphere triggered by daytime temperature

Shilong Piao (1, 2) , Jianguang Tan (1) , Anping Chen (2, 3) , Yongshuo Fu (1, 4) , Philippe Ciais (5, 6) , Qiang Liu (1) , Ivan Janssens (4) , Sara Vicca (4) , Zhenzhong Zeng (1) , Su-Jong Jeong (7) , Yue Li (1) , Ranga Myneni (8) , Shushi Peng (1, 5) , Miaogen Shen (2) , Josep Peñuelas (9)

1 Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences
2 CAS - Chinese Academy of Sciences [Beijing]
3 Princeton University
4 UA - University of Antwerp
5 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
6 ICOS-ATC - ICOS-ATC
7 CALTECH - California Institute of Technology
8 BU - Boston University [Boston]
9 CREAF - Centre for Ecological Research and Applied Forestries

Recent warming significantly advanced leaf onset in the northern hemisphere. This signal cannot be accurately reproduced by current models parameterized by daily mean temperature (T mean). Here using in situ observations of leaf unfolding dates (LUDs) in Europe and the United States, we show that the interannual anomalies of LUD during 1982-2011 are triggered by daytime (T max) more than by nighttime temperature (T min). Furthermore, an increase of 1°C in T max would advance LUD by 4.7 days in Europe and 4.3 days in the United States, more than the conventional temperature sensitivity estimated from T mean. The triggering role of T max , rather than the T min or T mean variable, is also supported by analysis of the large-scale patterns of satellite-derived vegetation green-up in spring in the northern hemisphere (430°N). Our results suggest a new conceptual framework of leaf onset using daytime temperature to improve the performance of phenology modules in current Earth system models.

Domaines: Océan, Atmosphère; Interfaces continentales, environnement

Shilong Piao, Jianguang Tan, Anping Chen, Yongshuo Fu, Philippe Ciais, et al.. Leaf onset in the northern hemisphere triggered by daytime temperature. Nature Communications, 2015, 6 (1), ⟨10.1038/ncomms7911⟩. ⟨hal-01806233⟩