Converging Climate Sensitivities of European Forests Between Observed Radial Tree Growth and Vegetation Models

Zhen Zhang (1, 2, 3) , Flurin Babst (1, 4) , Valentin Bellassen (5) , David Frank (6) , Thomas Launois (7) , Kun Tan (7) , Philippe Ciais (7, 8) , Benjamin Poulter (2, 9)

1 Swiss Federal Research Institute
2 Institute on Ecosystems and Department of Ecology [Bozeman]
3 Northwest Institute of Eco-Environment and Resources
4 W. Szafer Institute of Botany
5 CESAER - Centre d'Economie et de Sociologie Rurales Appliquées à l'Agriculture et aux Espaces Ruraux
6 Laboratory of Tree-Ring Research
7 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
8 ICOS-ATC - ICOS-ATC
9 Biospheric Science Laboratory

The impacts of climate variability and trends on European forests are unevenly distributed across different bioclimatic zones and species. Extreme climate events are also becoming more frequent and it is unknown how they will affect feedbacks of CO2 between forest ecosystems and the atmosphere. An improved understanding of species differences at the regional scale of the response of forest productivity to climate variation and extremes is thus important for forecasting forest dynamics. In this study, we evaluate the climate sensitivity of aboveground net primary production (NPP) simulated by two dynamic global vegetation models (DGVM; ORCHIDEE and LPJ-wsl) against tree ring width (TRW) observations from about 1000 sites distributed across Europe. In both the model simulations and the TRW observations, forests in northern Europe and the Alps respond positively to warmer spring and summer temperature, and their overall temperature sensitivity is larger than that of the soil-moisture-limited forests in central Europe and Mediterranean regions. Compared with TRW observations, simulated NPP from ORCHIDEE and LPJ-wsl appear to be overly-sensitive to climatic factors. Our results indicate that the models lack biological processes that control time lags, such as carbohydrate storage and remobilization, that delay the effects of radial growth dynamics to climate. Our study highlights the need for re-evaluating the physiological controls on the climate sensitivity of NPP simulated by DGVMs. In particular, DGVMs could be further enhanced by a more detailed representation of carbon reserves and allocation that control year-to-year variation in plant growth.

Mots clés: forest growth; ORCHIDEE; climate response; DGVM; LPJ; NPP; tree ring width; carbon cycle

Domaines: Sciences du Vivant [q-bio]

Zhen Zhang, Flurin Babst, Valentin Bellassen, David Frank, Thomas Launois, et al.. Converging Climate Sensitivities of European Forests Between Observed Radial Tree Growth and Vegetation Models. Ecosystems, 2017, 21 (3), pp.1-16. ⟨10.1007/s10021-017-0157-5⟩. ⟨hal-01608911⟩