Groundwater salinization intensifies drought impacts in forests and reduces refuge capacity

Kath, Jarrod and Powell, Sue and Reardon-Smith, Kathryn and El Sawah, Sondoss and Jakeman, Anthony J. and Croke, Barry F.W. and Dyer, Fiona J. (2015) Groundwater salinization intensifies drought impacts in forests and reduces refuge capacity. Journal of Applied Ecology, 52 (5). pp. 1116-1125. ISSN 0021-8901

Abstract

1. Shallow groundwater aquifers regularly support drought refuges for water-dependent ecosystems. However, many aquifers are impacted by over-extraction and pollution, potentially degrading their ability to support groundwater-fed drought refuges.
2. We investigated the response of groundwater-connected riverine forests to a drought considered equivalent in intensity to those predicted under severe climate change for 2030. The drought’s impact was investigated in an area where shallow groundwater resources are heavily
exploited and polluted by salinization.
3. We used remotely sensed vegetation productivity (enhanced vegetation index) data from a long-term data set (2000–2011) at 475 riverine forest sites in the Campaspe catchment, southeastern Australia. Generalized additive mixed models and boosted regression trees were used
to model the relationship between groundwater and other environmental covariates with forest change during drought.
4. Models explained up to 44% of the variation in forest change during drought. Forests underwent the greatest declines in areas of high salinity (>6000 lS cm-1) associated with shallow groundwater depths (0–5 m). Conversely, forests in areas of lowest salinity
(<2000 lS cm-1) and groundwater depths of more than 7-5 m showed the least decline during drought.
5. In landscapes where groundwater quality is not compromised, previous studies have shown that shallow groundwater provides important drought refuges and refugia. Here, we show that when groundwater salinization has occurred, forests connected to shallow groundwater
are more vulnerable to drought. In effect, salinization reduces the capacity of groundwater-connected habitats to function as drought refuges.
6. Synthesis and applications. Currently, there is an emphasis on managing environmental flows to support freshwater ecosystems and associated forests under water stress. However, delivery of environmental water is restricted to areas within a linear stream network and there
is often limited capacity to deliver environmental flows during drought. Alternatively, a focus on drought refuges and refugia and processes important for maintaining groundwater quality (e.g. catchment revegetation to reduce shallow groundwater salinization) may better allow
drought effects to be managed across a catchment, without directly focusing on highly contested surface water resources.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Permanent restricted access to published version in accordance with the copyright policy of the publisher.
Faculty / Department / School: No Faculty
Date Deposited: 22 Apr 2016 01:56
Last Modified: 14 Feb 2017 01:04
Uncontrolled Keywords: aquifer; drought; forest; groundwater; refugia; revegetation; salinity
Fields of Research : 05 Environmental Sciences > 0502 Environmental Science and Management > 050205 Environmental Management
05 Environmental Sciences > 0501 Ecological Applications > 050101 Ecological Impacts of Climate Change
Socio-Economic Objective: D Environment > 96 Environment > 9608 Flora, Fauna and Biodiversity > 960806 Forest and Woodlands Flora, Fauna and Biodiversity
D Environment > 96 Environment > 9609 Land and Water Management > 960907 Forest and Woodlands Water Management
D Environment > 96 Environment > 9605 Ecosystem Assessment and Management > 960506 Ecosystem Assessment and Management of Fresh, Ground and Surface Water Environments
Identification Number or DOI: 10.1111/1365-2664.12495
URI: http://eprints.usq.edu.au/id/eprint/27604

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