Holocene vegetation and biomass changes on the Tibetan Plateau – a model-pollen data comparison 1Max Planck Institute for Meteorology, KlimaCampus Hamburg, Germany
12 Aug 2011
2Meteorological Institute, University of Hamburg, KlimaCampus Hamburg, Germany
3Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany
4International Max-Planck-Research School, Hamburg, Germany
Received: 17 Feb 2011 – Published in Clim. Past Discuss.: 31 Mar 2011 Abstract. Results of a transient numerical experiment performed in a coupled
atmosphere-ocean-vegetation model with orbital forcing alone are compared
to pollen-based vegetation reconstructions covering the last 6000 yr from four representative sites on
the Tibetan Plateau. Causes of the vegetation
change and consequences of the biomass storage are analysed.
Revised: 19 Jul 2011 – Accepted: 28 Jul 2011 – Published: 12 Aug 2011
In general, simulated and reconstructed vegetation trends at each site are
in good agreement. Both methods reveal a general retreat of the biomass-rich
vegetation that is particularly manifested in a strong decrease of forests.
However, model and reconstructions often differ with regard to the climatic
factors causing the vegetation change at each site. The reconstructions
primarily identify decreasing summer monsoon precipitation and changes in
the temperature of the warm season as the responsible mechanisms for the
vegetation shift. In the model, the land cover change mainly originates from
differences in warm/cold seasonal temperatures and only to a lesser extent
from precipitation changes.
According to the model results, the averaged forest fraction on the Plateau
shrinks by almost one-third from mid-Holocene (41.4 %) to present-day
(28.3 %). Shrubs, whose fraction is quadrupled at present-day (12.3 %),
replace most of this forest. Grass fraction increases from 38.1 % during
the mid-Holocene to 42.3 % at present-day. This land cover change results
in a decrease of living biomass by 0.62 kgC m−2. Total biomass on the
Tibetan Plateau decreases by 1.9 kgC m−2, i.e. approx. 6.64 PgC are
released due to the natural land cover change.
Citation: Dallmeyer, A., Claussen, M., Herzschuh, U., and Fischer, N.: Holocene vegetation and biomass changes on the Tibetan Plateau – a model-pollen data comparison, Clim. Past, 7, 881-901, doi:10.5194/cp-7-881-2011, 2011.