Rain use efficiency gradients across Australian ecosystems

Zhongli Liu; Grzegorz Skrzypek; Okke Batelaan; Huade Guan

doi:10.1016/j.scitotenv.2024.173101

Rain use efficiency gradients across Australian ecosystems

Sci Total Environ. 2024 May 9:933:173101. doi: 10.1016/j.scitotenv.2024.173101. Online ahead of print.

Authors

Zhongli Liu¹, Grzegorz Skrzypek², Okke Batelaan¹, Huade Guan³

Affiliations

¹ National Centre for Groundwater Research and Training, College of Science and Engineering, Flinders University, Adelaide, SA, Australia.
² West Australian Biogeochemistry Centre, School of Biological Sciences, The University of Western Australia, Perth, WA, Australia.
³ National Centre for Groundwater Research and Training, College of Science and Engineering, Flinders University, Adelaide, SA, Australia. Electronic address: huade.guan@flinders.edu.au.

PMID: 38734114
DOI: 10.1016/j.scitotenv.2024.173101

Abstract

Rain use efficiency (RUE) quantifies the ecosystem's capacity to use precipitation water to assimilate atmospheric CO₂. The spatial distribution of RUE and its drivers across the Australian continent is largely unknown. This knowledge gap limits our understanding of the possible contribution of Australian ecosystems to global carbon assimilation. This study investigates the spatial distribution of RUE across diverse terrestrial ecosystems in Australia. The results show that RUE ranges from 0.43 (1st percentile) to 3.10 (99th percentile) g C m^-2 mm^-1 with a continental mean of 1.19 g C m^-2 mm^-1. About 68 % of the spatiotemporal variability of RUE can be explained by a multiple linear regression model primarily contributed by climatic predictors. Benchmarked by the model estimation, drainage-diverging/converging landscapes tend to have reduced/increased RUE. The model also revealed the impact of increasing atmospheric CO₂ concentration on RUE. The continental mean RUE would increase by between 29.3 and 64.8 % by the end of this century under the SSP5-8.5 scenario in which the CO₂ concentration is projected to double from the present level. This increase in projected RUE is attributed to the assumed greening effect of increasing CO₂ concentration, which does not consider the saturation of CO₂ fertilisation effect and the warming effect on increasing wildfire occurrence. Under the SSP1-2.6 scenario, RUE would decrease by about 7 %. This study provides baseline RUEs of various ecosystems in Australia for investigating the impacts of human interferences and climate change on the capacity of Australian vegetation to assimilate atmospheric CO₂ under given precipitation.

Keywords: Australia; Climate change; Gross primary productivity; Rain use efficiency; Terrestrial ecosystems.