Controls on transpiration in a semiarid riparian cottonwood forest

Gazal, Rico; Scott, Russell L.; Goodrich, David C.; Williams, David G.

doi:10.1016/j.agrformet.2006.03.002

Cited by 116 publications

(103 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The upland vegetation that previously occupied riverine upper terraces and grasslands supported small rates of ET (Shafroth et al, 2005;Hultine and Bush, 2011); thus, expansion of phreatophytes into these areas has resulted in an increase in ET losses (Scott et al, 2006b; and thereby has placed a potential strain on groundwater resources. In the case of expansion by Tamarix, groundwater extraction may result in enhancement of ET , contrasting with post-extraction reductions in ET by native, shallow-rooted phreatophytes such as Populus (Cooper et al, 2006;Gazal et al, 2006) and thus representing a shift in the ecohydrology of riparian corridors throughout the semi-arid regions of south-western North America.…”

Section: The Gnangara Moundmentioning

confidence: 99%

“…cottonwood, Populus spp.) can be very sensitive to groundwater decline, resulting in reductions of ET, productivity and canopy conductance as a consequence of increases in vapour pressure deficit that are correlated with depth-to-groundwater (Gazal et al, 2006;Kochendorfer et al, 2011). Branch sacrifice, partial crown dieback and mortality commonly occur in Populus following substantial groundwater drawdown (Mahoney and Rood, 1991;Kranjcec et al, 1998;Scott et al, 1999;Rood et al, 2000Rood et al, , 2003Cooper et al, 2003).…”

Section: The Gnangara Moundmentioning

confidence: 99%

See 1 more Smart Citation

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

Eamus

Zolfaghar

Villalobos‐Vega

et al. 2015

Hydrol. Earth Syst. Sci.

132

112

View full text Add to dashboard Cite

Abstract. Groundwater-dependent ecosystems (GDEs) are at risk globally due to unsustainable levels of groundwater extraction, especially in arid and semi-arid regions. In this review, we examine recent developments in the ecohydrology of GDEs with a focus on three knowledge gaps: (1) how do we locate GDEs, (2) how much water is transpired from shallow aquifers by GDEs and (3) what are the responses of GDEs to excessive groundwater extraction? The answers to these questions will determine water allocations that are required to sustain functioning of GDEs and to guide regulations on groundwater extraction to avoid negative impacts on GDEs.We discuss three methods for identifying GDEs: (1) techniques relying on remotely sensed information; (2) fluctuations in depth-to-groundwater that are associated with diurnal variations in transpiration; and (3) stable isotope analysis of water sources in the transpiration stream.We then discuss several methods for estimating rates of GW use, including direct measurement using sapflux or eddy covariance technologies, estimation of a climate wetness index within a Budyko framework, spatial distribution of evapotranspiration (ET) using remote sensing, groundwater modelling and stable isotopes. Remote sensing methods often rely on direct measurements to calibrate the relationship between vegetation indices and ET. ET from GDEs is also determined using hydrologic models of varying complexity, from the White method to fully coupled, variable saturation models. Combinations of methods are typically employed to obtain clearer insight into the components of groundwater discharge in GDEs, such as the proportional importance of transpiration versus evaporation (e.g. using stable isotopes) or from groundwater versus rainwater sources.Groundwater extraction can have severe consequences for the structure and function of GDEs. In the most extreme cases, phreatophytes experience crown dieback and death following groundwater drawdown. We provide a brief review of two case studies of the impacts of GW extraction and then provide an ecosystem-scale, multiple trait, integrated metric of the impact of differences in groundwater depth on the structure and function of eucalypt forests growing along a natural gradient in depth-to-groundwater. We conclude with a discussion of a depth-to-groundwater threshold in this mesic GDE. Beyond this threshold, significant changes occur in ecosystem structure and function.

show abstract

Section: The Gnangara Moundmentioning

confidence: 99%

Section: The Gnangara Moundmentioning

confidence: 99%

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

Eamus

Zolfaghar

Villalobos‐Vega

et al. 2015

Hydrol. Earth Syst. Sci.

132

112

View full text Add to dashboard Cite

show abstract

“…The simulations are intended to reflect the hydrology of riparian vegetation in Mediterranean or semi-arid/desert climates that meet atmospheric evaporative demand and avoid drought stress with the help of deep roots that exploit groundwater or soil water in the capillary fringe (Zencich et al, 2002;Lamontagne et al, 2005;Cleverly et al, 2006;Gazal et al, 2006). A 100-day dry period was modeled without rain.…”

Section: Water Uptake By Riparian Forestmentioning

confidence: 99%

“…Indeed, water uptake from deep subsoil has been shown to be critical in meeting atmospheric transpiration demand in water-limited environments (e.g. Jipp et al, 1998;Oliveira et al, 2005), especially where roots can reach shallow groundwater (Zhang et al, 1999;Zencich et al, 2002;Lamontagne et al, 2005;Cleverly et al, 2006;Gazal et al, 2006;Paço et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Simple physics-based models of compensatory plant water uptake: concepts and eco-hydrological consequences

Jarvis¹

2011

Hydrol. Earth Syst. Sci.

102

View full text Add to dashboard Cite

Abstract. Many land surface schemes and simulation models of plant growth designed for practical use employ simple empirical sub-models of root water uptake that cannot adequately reflect the critical role water uptake from sparsely rooted deep subsoil plays in meeting atmospheric transpiration demand in water-limited environments, especially in the presence of shallow groundwater. A failure to account for this so-called "compensatory" water uptake may have serious consequences for both local and global modeling of water and energy fluxes, carbon balances and climate. Some purely empirical compensatory root water uptake models have been proposed, but they are of limited use in global modeling exercises since their parameters cannot be related to measurable soil and vegetation properties. A parsimonious physicsbased model of uptake compensation has been developed that requires no more parameters than empirical approaches. This model is described and some aspects of its behavior are illustrated with the help of example simulations. These analyses demonstrate that hydraulic lift can be considered as an extreme form of compensation and that the degree of compensation is principally a function of soil capillarity and the ratio of total effective root length to potential transpiration. Thus, uptake compensation increases as root to leaf area ratios increase, since potential transpiration depends on leaf area. Results of "scenario" simulations for two case studies, one at the local scale (riparian vegetation growing above shallow water tables in seasonally dry or arid climates) and one at a global scale (water balances across an aridity gradient in the continental USA), are presented to illustrate biasesCorrespondence to: N. J. Jarvis (nicholas.jarvis@slu.se) in model predictions that arise when water uptake compensation is neglected. In the first case, it is shown that only a compensated model can match the strong relationships between water table depth and leaf area and transpiration observed in riparian forest ecosystems, where sparse roots in the capillary fringe contribute a significant proportion of the water uptake during extended dry periods. The results of the second case study suggest that uncompensated models may give biased estimates of long-term evapotranspiration at the continental scale. In the example presented here, the uncompensated model underestimated total evapotranspiration by 5-7 % in climates of intermediate aridity, while the ratio of transpiration to evaporation was also smaller than for the compensated model, especially in arid climates. It is concluded that the parsimonious physics-based model concepts described here may be useful in the context of eco-hydrological modeling at local, regional and global scales.

show abstract

“…Considerable spatial variation in phreatophyte groundwater uptake has been observed [5], and may vary with depth to groundwater and intermittency of surface water [13,20,38]. Human activities (e.g.…”

Section: Discussionmentioning

confidence: 99%

An analytic solution for groundwater uptake by phreatophytes spanning spatial scales from plant to field to regional

Steward

Ahring

2008

J Eng Math

View full text Add to dashboard Cite

Phreatophytes are important to the overall hydrologic water budget, providing pathways from the uptake of groundwater with its nutrients and chemicals to subsequent discharge to the root zone through hydraulic lift and to the atmosphere through evapotranspiration. An analytic mathematical model is developed to model groundwater uptake by individual plants and fields of plant communities and the regional hydrology of communities of fields. This model incorporates new plant functions developed through aid of Wirtinger calculus. Existing methodology for area-sinks is extended to fields of phreatophytes, and Bell polynomials are employed to extend existing numerical methods to calculate regional coefficients for area-sinks. This model is used to develop capture zones for individual phreatophytes and it is shown that the functional form of groundwater uptake impacts capture zone topology, with groundwater being extracted from greater depths when root water uptake is focused about a taproot. While individual plants siphon groundwater from near the phreatic surface, it is shown that communities of phreatophytes may tap groundwater from greater depths and lateral extent as capture zones pass beneath those of upgradient phreatophytes. Thus, biogeochemical pathways moving chemical inputs from aquifer to ecosystems are influenced by both the distribution of groundwater root uptake and the proximity of neighboring phreatophytes. This provides a computational platform to guide hypothesis testing and field instrumentation and interpretation of their data and to understand the function of phreatophytes in water and nutrient uptake across plant to regional scales.

show abstract

Controls on transpiration in a semiarid riparian cottonwood forest

Cited by 116 publications

References 32 publications

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

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

Simple physics-based models of compensatory plant water uptake: concepts and eco-hydrological consequences

An analytic solution for groundwater uptake by phreatophytes spanning spatial scales from plant to field to regional

Contact Info

Product

Resources

About