Identifying areas at risk of drought-induced tree mortality across South-Eastern Australia

Martin G De Kauwe; Belinda E Medlyn; Anna M Ukkola; Mengyuan Mu; Manon E B Sabot; Andrew J Pitman; Patrick Meir; Lucas A Cernusak; Sami W Rifai; Brendan Choat; David T Tissue; Chris J Blackman; Ximeng Li; Michael Roderick; Peter R Briggs

doi:10.1111/gcb.15215

Identifying areas at risk of drought-induced tree mortality across South-Eastern Australia

Glob Chang Biol. 2020 Oct;26(10):5716-5733. doi: 10.1111/gcb.15215. Epub 2020 Aug 19.

Authors

Martin G De Kauwe^{1

2

3}, Belinda E Medlyn⁴, Anna M Ukkola^{1

5}, Mengyuan Mu^{1

2}, Manon E B Sabot^{1

2

3}, Andrew J Pitman^{1

2}, Patrick Meir^{6

7}, Lucas A Cernusak⁸, Sami W Rifai², Brendan Choat⁴, David T Tissue⁴, Chris J Blackman⁴, Ximeng Li⁴, Michael Roderick^{1

5}, Peter R Briggs⁹

Affiliations

¹ ARC Centre of Excellence for Climate Extremes, Sydney, NSW, Australia.
² Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia.
³ Evolution & Ecology Research Centre, University of New South Wales, Sydney, NSW, Australia.
⁴ Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia.
⁵ Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia.
⁶ Research School of Biology, The Australian National University, Acton, ACT, Australia.
⁷ School of Geosciences, University of Edinburgh, Edinburgh, UK.
⁸ College of Science and Engineering, James Cook University, Cairns, Qld, Australia.
⁹ CSIRO Oceans and Atmosphere, Canberra, ACT, Australia.

PMID: 32512628
DOI: 10.1111/gcb.15215

Abstract

South-East Australia has recently been subjected to two of the worst droughts in the historical record (Millennium Drought, 2000-2009 and Big Dry, 2017-2019). Unfortunately, a lack of forest monitoring has made it difficult to determine whether widespread tree mortality has resulted from these droughts. Anecdotal observations suggest the Big Dry may have led to more significant tree mortality than the Millennium drought. Critically, to be able to robustly project future expected climate change effects on Australian vegetation, we need to assess the vulnerability of Australian trees to drought. Here we implemented a model of plant hydraulics into the Community Atmosphere Biosphere Land Exchange (CABLE) land surface model. We parameterized the drought response behaviour of five broad vegetation types, based on a common garden dry-down experiment with species originating across a rainfall gradient (188-1,125 mm/year) across South-East Australia. The new hydraulics model significantly improved (~35%-45% reduction in root mean square error) CABLE's previous predictions of latent heat fluxes during periods of water stress at two eddy covariance sites in Australia. Landscape-scale predictions of the greatest percentage loss of hydraulic conductivity (PLC) of about 40%-60%, were broadly consistent with satellite estimates of regions of the greatest change in both droughts. In neither drought did CABLE predict that trees would have reached critical PLC in widespread areas (i.e. it projected a low mortality risk), although the model highlighted critical levels near the desert regions of South-East Australia where few trees live. Overall, our experimentally constrained model results imply significant resilience to drought conferred by hydraulic function, but also highlight critical data and scientific gaps. Our approach presents a promising avenue to integrate experimental data and make regional-scale predictions of potential drought-induced hydraulic failure.

Keywords: Australia; cavitation resistance; drought tolerance; land surface model; plant hydraulics.

MeSH terms

Australia
Climate Change
Droughts*
Plant Leaves
Trees*
Water

Substances

Water

Abstract

MeSH terms

Substances

Grants and funding