Harmonising plant functional type distributions for evaluating Earth system models
<p>Dynamic vegetation models simulate global vegetation in terms of fractional coverage of a few plant functional types (PFTs). Although these models often share the same concept, they differ with respect to the number and kind of PFTs, complicating the comparability of simulated vegetation di...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-02-01
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| Series: | Climate of the Past |
| Online Access: | https://www.clim-past.net/15/335/2019/cp-15-335-2019.pdf |
| Summary: | <p>Dynamic vegetation models simulate global vegetation in terms of
fractional coverage of a few plant functional types (PFTs). Although these
models often share the same concept, they differ with respect to the number
and kind of PFTs, complicating the comparability of simulated vegetation
distributions. Pollen-based vegetation reconstructions are initially only
available in the form of time series of individual taxa that are not
distinguished in the models. Thus, to evaluate simulated vegetation
distributions, the modelling results and pollen-based vegetation
reconstructions have to be converted into a comparable format. The classical
approach is the method of biomisation, but hitherto PFT-based biomisation
methods were only available for individual models. We introduce and evaluate
a simple, universally applicable technique to harmonise PFT distributions by
assigning them into nine mega-biomes, using only assumptions on the minimum
PFT cover fractions and few bioclimatic constraints (based on the
2 m temperature). These constraints mainly follow the limitation rules used in
the classical biome models (here BIOME4). We test the method for six
state-of-the-art dynamic vegetation models that are included in Earth system
models based on pre-industrial, mid-Holocene and Last Glacial Maximum
simulations. The method works well, independent of the spatial resolution or
the complexity of the models. Large biome belts (such as tropical forest) are
generally better represented than regionally confined biomes (warm–temperate
forest, savanna). The comparison with biome distributions inferred via the
classical biomisation approach of forcing biome models (here BIOME1) with
the simulated climate states shows that the PFT-based biomisation is even
able to keep up with the classical method. However, as the new method
considers the PFT distributions actually calculated by the Earth system models, it allows for a direct comparison and evaluation of simulated
vegetation distributions which the classical method cannot do. Thereby, the
new method provides a powerful tool for the evaluation of Earth system models
in general.</p> |
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| ISSN: | 1814-9324 1814-9332 |