Identifying groundwater thresholds for drought resilience in floodplain tree species in the northern Murray-Darling Basin

Reardon-Smith, Kate and Kath, Jarrod and Le Brocque, Andy and Dyer, Fiona (2014) Identifying groundwater thresholds for drought resilience in floodplain tree species in the northern Murray-Darling Basin. In: Ecological Society of Australia Annual Conference (ESA 2014), 28 Sep-3 Oct 2014 , Alice Springs, Australia.

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Abstract

Previous research identifies links between groundwater depth and canopy condition in dominant riparian and floodplain tree species associated with ephemeral river systems, particularly during drought. Chronic groundwater decline, evident in many agricultural landscapes worldwide, effectively decouples tree roots from deep soil moisture resources, increasing the susceptibility of trees to changes in precipitation. Drought may trigger loss of canopy condition and, where severe or prolonged, have long term consequences for the function and survival of trees and the composition, structure and function of ecosystems they dominate. However, critical groundwater depth thresholds, which may reflect ecological 'tipping points' in such systems, have been difficult to identify.
This study used boosted regression trees, quantile regression and Threshold Indicator Taxa Analysis to investigate the relationship between groundwater depth and tree condition for two dominant tree species, Eucalyptus camaldulensis (river red gum) and E. populnea (poplar box). Both occur on the Upper Condamine floodplain, a region experiencing significant groundwater decline due to unsustainable groundwater extraction in the northern Murray-Darling Basin, southern Queensland. Distinct non-linear responses were found, with groundwater depth thresholds identified at 12.1–22.6m for E. camaldulensis and 12.6–22.6m for E. populnea, beyond which canopy condition declined abruptly.
This approach represents a repeatable method of quantifying ecological response thresholds along groundwater depth gradients, application of which may assist in identifying safe operating limits for groundwater resource management to support resilient floodplain ecosystems. It will be particularly important in regions where increasing water demand and drying climates may drive further groundwater decline.


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Item Type: Conference or Workshop Item (Commonwealth Reporting Category E) (Speech)
Refereed: No
Item Status: Live Archive
Faculty / Department / School: No Faculty
Date Deposited: 14 Apr 2015 01:56
Last Modified: 14 Feb 2017 23:56
Uncontrolled Keywords: groundwater levels; river red gum; poplar tree; Australia; irrigation limits; canopy condition; dieback; drought; ecological threshold; groundwater dependent ecosystems; tipping point
Fields of Research : 05 Environmental Sciences > 0502 Environmental Science and Management > 050209 Natural Resource Management
05 Environmental Sciences > 0502 Environmental Science and Management > 050202 Conservation and Biodiversity
05 Environmental Sciences > 0501 Ecological Applications > 050104 Landscape Ecology
Socio-Economic Objective: D Environment > 96 Environment > 9608 Flora, Fauna and Biodiversity > 960807 Fresh, Ground and Surface Water Flora, Fauna and Biodiversity
D Environment > 96 Environment > 9613 Remnant Vegetation and Protected Conservation Areas > 961302 Protected Conservation Areas in Fresh, Ground and Surface Water Environments
URI: http://eprints.usq.edu.au/id/eprint/26173

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