Biome changes in Asia since the mid-Holocene – an analysis of different transient Earth system model simulations
- 1Max Planck Institute for Meteorology, Bundesstraße 53, 20146 Hamburg, Germany
- 2Meteorological Institute, Centrum für Erdsystemforschung und Nachhaltigkeit (CEN), Universität Hamburg, Bundesstraße 55, 20146 Hamburg, Germany
- 3Institute of Biochemistry and Biology, University of Potsdam, Maulbeerallee 3, 14469 Potsdam, Germany
- 4Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Telegrafenberg A43, 14473 Potsdam, Germany
- 5State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Lincheng West Road 99, 550081 Guiyang, China
- 6Institute of Earth and Environmental Science, University of Potsdam, Karl-Liebknecht-Straße 24–25, 14476 Potsdam, Germany
- 7College of Resource Environment and Tourism, Capital Normal University, Beijing 100048, China
- 8Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, 27568 Bremerhaven, Germany
- 9Key Laboratory of Western China's Environmental Systems, College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China
- 10Institute of Geosciences, Christian-Albrechts Universität zu Kiel, Ludewig-Meyn-Str. 10–14, 24118 Kiel, Germany
- 11A. M. Obukhov Institute of Atmospheric Physics RAS, Pyzhevsky 3, 117019 Moscow, Russia
- 12Helmholtz Center Geesthacht, Institute for Coastal Research, 21502 Geesthacht, Germany
Abstract. The large variety of atmospheric circulation systems affecting the eastern Asian climate is reflected by the complex Asian vegetation distribution. Particularly in the transition zones of these circulation systems, vegetation is supposed to be very sensitive to climate change. Since proxy records are scarce, hitherto a mechanistic understanding of the past spatio-temporal climate–vegetation relationship is lacking. To assess the Holocene vegetation change and to obtain an ensemble of potential mid-Holocene biome distributions for eastern Asia, we forced the diagnostic biome model BIOME4 with climate anomalies of different transient Holocene climate simulations performed in coupled atmosphere–ocean(–vegetation) models. The simulated biome changes are compared with pollen-based biome records for different key regions.
In all simulations, substantial biome shifts during the last 6000 years are confined to the high northern latitudes and the monsoon–westerly wind transition zone, but the temporal evolution and amplitude of change strongly depend on the climate forcing. Large parts of the southern tundra are replaced by taiga during the mid-Holocene due to a warmer growing season and the boreal treeline in northern Asia is shifted northward by approx. 4° in the ensemble mean, ranging from 1.5 to 6° in the individual simulations, respectively. This simulated treeline shift is in agreement with pollen-based reconstructions from northern Siberia. The desert fraction in the transition zone is reduced by 21 % during the mid-Holocene compared to pre-industrial due to enhanced precipitation. The desert–steppe margin is shifted westward by 5° (1–9° in the individual simulations). The forest biomes are expanded north-westward by 2°, ranging from 0 to 4° in the single simulations. These results corroborate pollen-based reconstructions indicating an extended forest area in north-central China during the mid-Holocene. According to the model, the forest-to-non-forest and steppe-to-desert changes in the climate transition zones are spatially not uniform and not linear since the mid-Holocene.