Soil thawing regulates the spring growth onset in tundra and alpine biomes

• Published in: Science of The Total Environment
• Main Authors: Descals, Adrià, Verger, Aleixandre, Filella, Iolanda, Baldocchi, Dennis, Janssens, Ivan, Fu, Yongshuo, Piao, Shilong, Peaucelle, Marc, Ciais, Philippe, Peñuelas, Josep
• Other Authors: ICOS-ATC (ICOS-ATC), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), H2020 Marie Skłodowska-Curie Actions, MSCA: 891369 European Research Council, ERC: ERC-SyG-2013-610028 IMBALANCE-P SGR 2017-1005 Fonds Wetenschappelijk Onderzoek, FWO: G018319N PID2019-110521GB-I00, The authors would like to acknowledge the financial support from the European Research Council Synergy grant ERC-SyG-2013-610028 IMBALANCE-P, the Spanish Government grant PID2019-110521GB-I00 and the Catalan Government grant SGR 2017-1005 . M.P. acknowledges the financial support from the Fonds Wetenschappelijk Onderzoek (FWO; grant no. G018319N ) and the H2020 Marie Skłodowska-Curie Actions (LEAF-2-TBM grant no. 891369 ).
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: Tundra; Thawing; Spring onset; Plant phenology; Deciduous forests; Boreal forests; [SDE]Environmental Sciences
• Online Access: https://hal.archives-ouvertes.fr/hal-03032256; https://hal.archives-ouvertes.fr/hal-03032256/document; https://hal.archives-ouvertes.fr/hal-03032256/file/ste.pdf; https://doi.org/10.1016/j.scitotenv.2020.140637

International audience Soil temperature remains isothermal at 0 °C and water shifts to a liquid phase during soil thawing. Vegetation may receive this process as a signal and a key to restore physiological activity. We aimed to show the relationship between the timing of soil thawing and the spring growth onset. We estimated the delay between the soil thawing and the spring growth onset in 78 sites of the FLUXNET network. We built a soil thawing map derived from modeling for the northern hemisphere and related it to the greenness onset estimated with satellite imagery. Spring onset estimated with GPP time series occurred shortly after soil surface thawing in tundra (1.1 ± 3.5 days) and alpine grasslands (16.6 ± 5.8 days). The association was weaker for deciduous forests (40.3 ± 4.2 days), especially where soils freeze infrequently. Needleleaved forests tended to start the growing season before the end of thawing (−17.4 ± 3.6 days), although observations from remote sensing (MODIS Land Cover Dynamics) indicated that the onset of greenness started after the thawing period (26.8 ± 3.2 days). This study highlights the role of soil temperature at the spring growth onset at high latitudes. Soil thawing becomes less relevant in temperate forests, where soil is occasionally frozen and other climate factors become more important.