Abstract
Riparian trees play a critical role in the ecological function of rivers, yet are threatened by anthropogenic change to the hydrological cycle. Identifying the sources of water used by riparian trees can inform sustainable water policy. We used isotopic analysis complemented by measurements of plant water relations to assess water sources for riparian trees at two sites with contrasting hydrogeological processes; one with an alluvial aquifer overlaying an aquitard, and one where fault-induced preferential pathways in the aquitard allowed the flow of deeper, older groundwater from a regional aquifer to the alluvium. At both sites, plant water potential, stomatal conductance, and plant water isotope composition in the xylem sap of riparian trees were collected from two landscape positions, the riverbank and floodplain. We used a Bayesian mixing model (MixSIAR) to assess differences in the proportion of water sources for sites and landscape positions. We found that xylem water isotope values differed between the two sites in line with their hydrogeological characteristics, with trees at the regional aquifer site using water sourced from the regional groundwater and trees at the site with only an alluvial aquifer present using a mixture of water sources, with no dominant source identified. Higher plant predawn water potential values at the regional site indicated greater water availability and support the inference that plants were using more groundwater at the regional site compared to the alluvial site. Trees closer to the river had higher isotope values, indicative of surficial water sources i.e. shallow soil water and river water. Our findings show that the water sources used by riparian trees reflect local hydrogeology and resource availability. Water managers should identify and protect plant water sources to ensure maintenance of riparian trees.
| Original language | English |
|---|---|
| Article number | e14180 |
| Pages (from-to) | 1-11 |
| Number of pages | 11 |
| Journal | Hydrological Processes |
| Volume | 35 |
| Issue number | 5 |
| Early online date | 18 Apr 2021 |
| DOIs | |
| Publication status | Published - May 2021 |
Bibliographical note
Funding Information:We thank the Walalakoo, and Yungngora Prescribed Bodies Corporate for providing us with permission to undertake research on their country. We thank Traditional Owners and Indigenous rangers for accompanying us on country, assisting with data collection and sharing knowledge about the land. We also thank Myroodah, and Noonkanbah Pastoral stations for access to study sites. We acknowledge the assistance of the Kimberley Land Council in project facilitation, particularly Karen Dayman. This project is supported through funding from the Australian Government's National Environmental Science Program through the Northern Australia Environmental Resources Hub.
Funding Information:
We thank the Walalakoo, and Yungngora Prescribed Bodies Corporate for providing us with permission to undertake research on their country. We thank Traditional Owners and Indigenous rangers for accompanying us on country, assisting with data collection and sharing knowledge about the land. We also thank Myroodah, and Noonkanbah Pastoral stations for access to study sites. We acknowledge the assistance of the Kimberley Land Council in project facilitation, particularly Karen Dayman. This project is supported through funding from the Australian Government's National Environmental Science Program through the Northern Australia Environmental Resources Hub.
Publisher Copyright:
© 2021 John Wiley & Sons Ltd.
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
