Groundwater-dependent ecosystems: recent insights from satellite and field-based studies

Eamus, Derek; Zolfaghar, Sepideh; Villalobos‐Vega, Randol; Cleverly, James; Huete, Alfredo

doi:10.5194/hess-19-4229-2015

Cited by 128 publications

(115 citation statements)

References 221 publications

(279 reference statements)

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“…Furthermore, T. ramosissima exhibits more plastic rooting ability for extracting water from dry soil than Populus euphratica does (Horton & Clark, 2001;Li, Yu, et al, 2013). Due to the limited water supply from surface flows, desert riparian forests in this hyperarid area are considered groundwater dependent ecosystems (GDEs) (Eamus, Zolfaghar, Villalobos-Vega, Cleverly, & Huete, 2015;Fu, Chen, & Li, 2013;Liu, Guan, Zhao, Yang, & Li, 2017). Due to the limited water supply from surface flows, desert riparian forests in this hyperarid area are considered groundwater dependent ecosystems (GDEs) (Eamus, Zolfaghar, Villalobos-Vega, Cleverly, & Huete, 2015;Fu, Chen, & Li, 2013;Liu, Guan, Zhao, Yang, & Li, 2017).…”

Section: Introductionmentioning

confidence: 99%

Responses of two desert riparian species to fluctuating groundwater depths in hyperarid areas of Northwest China

Tong

Huang

et al. 2019

Ecohydrology

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In the hyperarid region of Northwest China, frequent variations in hydrological environments present challenges to the persistence of riparian plants. The main objective of this study was to determine whether two desert riparian species (Populus euphratica and Tamarix ramosissima) differed in their water uptake patterns and ecophysiological responses to fluctuating groundwater depths (GWDs). This study was conducted in typical desert riparian ecosystems in the downstream Heihe River basin, Northwestern China, where the GWD continuously increases during growing season. Stable oxygen composition (δ 18 O) in xylem water, soil water, and groundwater, as well as leaf water potential and gas exchange were monitored. Results showed that P. euphratica used a higher ratio of soil water, whereas T. ramosissima relied more on groundwater and deep soil water. As the GWD increased during the growing season, both species modified their water use patterns, but they did so differently, P. euphratica extracted an increasing proportion of deep soil water and groundwater, whereas T. ramosissima took an increasing ratio of groundwater at critical growth stages. P. euphratica exhibited decreases in its daily maximum photosynthetic rate (A max ) and stomatal conductance (g max ) as the GWD increased, whereas those of T. ramosissima changed little. In summary, both species shift to use greater ratio of more reliable water sources with the increasing GWD, but the switching of water sources could not sufficiently compensate for the impact of drought stress on gas exchange for P. euphratica.

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Section: Introductionmentioning

confidence: 99%

Responses of two desert riparian species to fluctuating groundwater depths in hyperarid areas of Northwest China

Tong

Huang

et al. 2019

Ecohydrology

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“…; Eamus et al . ) with maximum rooting depths reaching about 60 m for Eucalyptus trees (Stone & Kalisz ).…”

Section: Introductionmentioning

confidence: 99%

Importance of deep water uptake in tropical eucalypt forest

et al. 2016

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Climate models predict that the frequency, intensity and duration of drought events will increase in tropical regions. Although water withdrawal from deep soil layers is generally considered to be an efficient adaptation to drought, there is little information on the role played by deep roots in tropical forests. Tropical Eucalyptus plantations managed in short rotation cycles are simple forest ecosystems that may provide an insight into the water use by trees in tropical forests. The contribution made by water withdrawn from deep soil layers to the water required for evapotranspiration was quantified daily from planting to harvesting age for a Eucalyptus grandis stand using a soil water transfer model coupled with an ecophysiological forest model (MAESPA). The model was parameterized using an extensive data set and validated using time series of the soil water content down to a depth of 10 m and water-table level, as well as evapotranspiration measured using eddy covariance. Fast root growth after planting provided access to large quantities of water stored in deep soil layers over the first 2 years. Eucalyptus roots reached the water-table at a depth of 12 m after 2 years. Although the mean water withdrawal from depths of over 10 m amounted to only 5% of canopy transpiration from planting to a harvesting age of 5 years, the proportion of water taken up near the water-table was much higher during dry periods. The water-table rose from 18 to 12 m below-ground over 2 years after the harvest of the previous stand and then fell until harvesting age as evapotranspiration rates exceeded the annual rainfall. Deep rooting is an efficient strategy to increase the amount of water available for the trees, allowing the uptake of transient gravitational water and possibly giving access to a deep water-table. Deep soil layers have an important buffer role for large amounts of water stored during the wet season that is taken up by trees during dry periods. Our study confirms that deep rooting could be a major mechanism explaining high transpiration rates throughout the year in many tropical forests. (Résumé d'auteur

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“…These lateral redistribution processes supply water for evapotranspiration in groundwater-dependent ecosystems in the dry season (Fan and Miguez-Macho, 2010). Several case studies in the Amazon (Christoffersen et al, 2014), central Argentina (Contreras et al, 2011;Jobbágy et al, 2011), and other groundwater-dependent ecosystems (Eamus et al, 2015) demonstrate how water supply can govern the seasonality and magnitude of evapotranspiration in those regions. However, the potential effects of these lateral redistribution processes on grid-scale ET, as viewed from the atmosphere, are missing from current Earth system models, and the resulting biases in modeled water fluxes are unknown.…”

Section: Introductionmentioning

confidence: 99%

A Budyko framework for estimating how spatial heterogeneity and lateral moisture redistribution affect average evapotranspiration rates as seen from the atmosphere

Freund

Kirchner

2017

Hydrol. Earth Syst. Sci.

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Abstract. Most Earth system models are based on gridaveraged soil columns that do not communicate with one another, and that average over considerable sub-grid heterogeneity in land surface properties, precipitation (P ), and potential evapotranspiration (PET). These models also typically ignore topographically driven lateral redistribution of water (either as groundwater or surface flows), both within and between model grid cells. Here, we present a first attempt to quantify the effects of spatial heterogeneity and lateral redistribution on grid-cell-averaged evapotranspiration (ET) as seen from the atmosphere over heterogeneous landscapes. Our approach uses Budyko curves, as a simple model of ET as a function of atmospheric forcing by P and PET. From these Budyko curves, we derive a simple sub-grid closure relation that quantifies how spatial heterogeneity affects average ET as seen from the atmosphere. We show that averaging over sub-grid heterogeneity in P and PET, as typical Earth system models do, leads to overestimations of average ET. For a sample high-relief grid cell in the Himalayas, this overestimation bias is shown to be roughly 12 %; for adjacent lower-relief grid cells, it is substantially smaller. We use a similar approach to derive sub-grid closure relations that quantify how lateral redistribution of water could alter average ET as seen from the atmosphere. We derive expressions for the maximum possible effect of lateral redistribution on average ET, and the amount of lateral redistribution required to achieve this effect, using only estimates of P and PET in possible source and recipient locations as inputs. We show that where the aridity index P /PET increases with altitude, gravitationally driven lateral redistribution will increase average ET (and models that overlook lateral redistribution will underestimate average ET). Conversely, where the aridity index P /PET decreases with altitude, gravitationally driven lateral redistribution will decrease average ET. The effects of both sub-grid heterogeneity and lateral redistribution will be most pronounced where P is inversely correlated with PET across the landscape. Our analysis provides first-order estimates of the magnitudes of these sub-grid effects, as a guide for more detailed modeling and analysis.

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Groundwater-dependent ecosystems: recent insights from satellite and field-based studies

Cited by 128 publications

References 221 publications

Responses of two desert riparian species to fluctuating groundwater depths in hyperarid areas of Northwest China

Responses of two desert riparian species to fluctuating groundwater depths in hyperarid areas of Northwest China

Importance of deep water uptake in tropical eucalypt forest

A Budyko framework for estimating how spatial heterogeneity and lateral moisture redistribution affect average evapotranspiration rates as seen from the atmosphere

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