University of Oulu

Dudley BD, Marttila H, Graham SL, Evison R, Srinivasan MS. Water sources for woody shrubs on hillslopes: An investigation using isotopic and sapflow methods. Ecohydrology. 2018;11:e1926. https://doi.org/10.1002/eco.1926

Water sources for woody shrubs on hillslopes : an investigation using isotopic and sapflow methods

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Author: Dudley, Bruce D.1; Marttila, Hannu2; Graham, Scott L.1;
Organizations: 1National Institute of Water and Atmospheric Research (NIWA)Christchurch, New Zealand
2Water Resources and Environmental Engineering Research Unit, Faculty of Technology, University of OuluOulu, Finland
3National Institute of Water and Atmospheric Research (NIWA)Wellington, New Zealand
Format: article
Version: accepted version
Access: embargoed
Persistent link: http://urn.fi/urn:nbn:fi-fe2018052424616
Language: English
Published: John Wiley & Sons, 2018
Publish Date: 2018-10-25
Description:

Abstract

Shrub encroachment into grasslands is a globally occurring process, but resulting changes to catchment water flows and stores are not yet well understood. We examined seasonal patterns of water sources for regenerating woody shrubs in seasonally dry montane farmland. We compared stable isotope ratios of shrub stem water to soil water pools at various depths within the vadose zone, groundwater, and stream water. We compared the results of these water source analysis with riparian plant water uptake measured using sap flux sensors and some potential drivers of sap flow rates (soil moisture and meteorological data). The stable isotope data indicated that the shrubs derived the majority of their water from shallow soil (top 10 cm), during the summer growing season. Sapflow measurements provided support for the isotope results, as riparian shrubs showed a springtime peak in water use and reduced sapflow rates during late summer driven by intermittent drying of shallow soil layers. Analysis of groundwater and streamwater indicated that these water sources were isotopically separated from plant and shallow soil water and fed primarily by precipitation falling during winter months. Our results indicate that transpiration of groundwater that may otherwise have fed streamflow is likely to be minor during early stages of shrub regeneration. This is important because shrubs are costly to remove and also have measureable benefits for sediment retention and soil fertility on montane farms.

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Series: Ecohydrology
ISSN: 1936-0584
ISSN-E: 1936-0592
ISSN-L: 1936-0584
Volume: 11
Issue: 2
Article number: e1926
DOI: 10.1002/eco.1926
OADOI: https://oadoi.org/10.1002/eco.1926
Type of Publication: A1 Journal article – refereed
Field of Science: 218 Environmental engineering
Subjects:
Funding: This research was funded by the NZ Ministry of Business, Innovation and Employment through WaterScape programme (contract C01X1006).
Copyright information: Copyright © 2017 John Wiley & Sons, Ltd. This is the peer reviewed version of the following article: Dudley BD, Marttila H, Graham SL, Evison R, Srinivasan MS. Water sources for woody shrubs on hillslopes: An investigation using isotopic and sapflow methods. Ecohydrology. 2018;11:e1926. https://doi.org/10.1002/eco.1926, which has been published in final form at https://doi.org/10.1002/eco.1926. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.