Abstract
Abstract. Future climate change has the potential to increase drought in many regions of the globe, making it essential that land surface models (LSMs) used in coupled climate models realistically capture the drought responses of vegetation. Recent data syntheses show that drought sensitivity varies considerably among plants from different climate zones, but state-of-the-art LSMs currently assume the same drought sensitivity for all vegetation. We tested whether variable drought sensitivities are needed to explain the observed large-scale patterns of drought impact on the carbon, water and energy fluxes. We implemented data-driven drought sensitivities in the Community Atmosphere Biosphere Land Exchange (CABLE) LSM and evaluated alternative sensitivities across a latitudinal gradient in Europe during the 2003 heatwave. The model predicted an overly abrupt onset of drought unless average soil water potential was calculated with dynamic weighting across soil layers. We found that high drought sensitivity at the most mesic sites, and low drought sensitivity at the most xeric sites, was necessary to accurately model responses during drought. Our results indicate that LSMs will over-estimate drought impacts in drier climates unless different sensitivity of vegetation to drought is taken into account.
Highlights
Changes in regional precipitation patterns with climate change are highly uncertain (Sillmann et al, 2014), but are widely expected to result in a change in the frequency, duration and severity of drought events (Allen et al, 2010)
Experimental data suggest that plants exhibit a continuum of drought sensitivities, with species originating in more mesic environments showing higher sensitivity than species from more xeric environments (Bahari et al, 1985; Reich and Hinckley, 1989; Ni and Pallardy, 1991; Zhou et al, 2014)
We investigated whether variable drought sensitivity improves the ability of the Community Atmosphere Biosphere Land Exchange (CABLE) land surface models (LSMs) to reproduce observed drought impacts across a latitudinal gradient
Summary
Changes in regional precipitation patterns with climate change are highly uncertain (Sillmann et al, 2014), but are widely expected to result in a change in the frequency, duration and severity of drought events (Allen et al, 2010). But for plants is a marked deficit of moisture in the root zone which results from a period of low rainfall and/or increased atmospheric demand for evapotranspiration. Drought and any ensuing vegetation mortality events have the potential to change land ecosystems from a sink to source (Lewis et al, 2011), and the dominant mechanisms governing the ecosystem responses to drought can vary from reducing stomatal conductance (Xu and Baldocchi, 2003) to increasing tree mortality (Lewis et al, 2011) and changing community species composition (Nepstad et al, 2007). De Kauwe et al.: Do models need to include differential plant species responses to drought?
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