Water Uptake by Roots Controls Water Table Movement and Sediment Oxidation in Short
            <i>Spartina</i>
            Marsh

Dacey, John W. H.; Howes, Brian L.

doi:10.1126/science.224.4648.487

Cited by 171 publications

(124 citation statements)

References 22 publications

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“…As a first approximation, we represented plant water use as if the plants were anisohydric or hydrolabile: plants that continue using water at a relatively constant rate and do not exhibit water uptake limitation for extended periods. This assumption of temporally constant evapotranspiration is a good approximation for halophytes able to use osmotic regulation to extract water even at very low soil water contents [Marani et al, 2006]; it was also consistent with the constant rate of salt marsh plant water uptake observed in lysimeters [Dacey and Howes, 1984] and with most previous modeling approaches (see Table 1). In reality, each species, and even each individual plant, may experience water and/or salt limitation at a different time, to a different degree, under different conditions.…”

Section: Limitations Of the Modelssupporting

confidence: 66%

“…The intricate mosaic of root zone hydraulic conditions that emerged in the complex model due to the intersection of heterogeneous vegetative and hydrological influences constituted ecohydrological zonation. Although coastal hydrology and vegetation have separately been recognized as influencing salt marsh groundwater dynamics for nearly a century [e.g., Johnson and York, 1915;Chapman, 1938a;Mahall and Park, 1976c;Hemond and Fifield, 1982;Dacey and Howes, 1984;Harvey et al, 1987;Nuttle, 1988;Howes and Goehringer, 1994], a spatially explicit conceptual model that integrates both hydrogeological and ecological influences on salt marsh groundwater dynamics has not previously been proposed, which is what is captured in the concept of ecohydrological zonation. [54] Ecohydrological zonation encapsulates both visually obvious, above-ground wetland patterning and hidden, below-ground hydraulic patterning, which are each integral parts of overall wetland ecohydrology.…”

Section: Ecohydrological Zonationmentioning

confidence: 99%

“…In the uniform ET scenario, a spatially uniform, constant upward flux of 4 mm d À1 [Ursino et al, 2004] (see also Dacey and Howes [1984] as discussed by Li et al [2005]) was distributed linearly with depth through the top 0.2 m (two model layers) of sediments. The linear weighting approximated the decline in root biomass with depth observed in salt marshes, to an extinction depth [Chapman, 1938a;Howes et al, 1981;Ellison et al, 1986;Steinke et al, 1996;Boyer et al, 2000], and the greater effect of soil evaporation at the surface.…”

Section: Surface Boundary Conditions: Evapotranspiration Scenariosmentioning

confidence: 99%

“…[4] Salt marsh groundwater flow is represented in the literature by four somewhat conflicting conceptual models: (1) Flow in interior marsh sediments is entirely vertical because of alternating phases of evapotranspiration and infiltration governed by the tides [Hemond and Fifield, 1982;Dacey and Howes, 1984]. (2) Vertical flow in the marsh interior feeds deep, slow flow paths beneath the marsh that contribute to submarine groundwater discharge in the coastal zone .…”

Section: Introductionmentioning

confidence: 99%

“…[5] Expanding on the last of the above conceptual models, there are three notable features of salt marsh plantwater interactions: (1) Plant water use comprises a significant portion of the soil water balance and partially controls water table position [Dacey and Howes, 1984]. (2) Plant species take up water from the root zone at different rates because of differences in energy balance, photosynthetic metabolism, and water use efficiency [Teal and Kanwisher, 1970;Park, 1976a, 1976b;Antlfinger and Dunn, 1979;Giurgevich and Dunn, 1982].…”

Section: Introductionmentioning

confidence: 99%

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Salt marsh ecohydrological zonation due to heterogeneous vegetation–groundwater–surface water interactions

Moffett¹,

Gorelick²,

McLaren³

et al. 2012

Water Resources Research

112

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[1] Vegetation zonation and tidal hydrology are basic attributes of intertidal salt marshes, but specific links among vegetation zonation, plant water use, and spatiotemporally dynamic hydrology have eluded thorough characterization. We developed a quantitative model of an intensively studied salt marsh field site, integrating coupled 2-D surface water and 3-D groundwater flow and zonal plant water use. Comparison of model scenarios with and without heterogeneity in (1) evapotranspiration rates and rooting depths, according to mapped vegetation zonation, and (2) sediment hydraulic properties from inferred geological heterogeneity revealed the coupled importance of both sources of ecohydrological variability at the site. Complex spatial variations in root zone pressure heads, saturations, and vertical groundwater velocities emerged in the model but only when both sources of ecohydrological variability were represented together and with tidal dynamics. These regions of distinctive root zone hydraulic conditions, caused by the intersection of vegetation and sediment spatial patterns, were termed ''ecohydrological zones'' (EHZ). Five EHZ emerged from different combinations of sediment hydraulic properties and evapotranspiration rates, and two EHZ emerged from local topography. Simulated pressure heads and groundwater dynamics among the EHZ were validated with field data. The model and data showed that hydraulic differences between EHZ were masked shortly after a flooding tide but again became prominent during prolonged marsh exposure. We suggest that ecohydrological zones, which reflect the combined influences of topographic, sediment, and vegetation heterogeneity and do not emphasize one influence over the others, are the fundamental spatial habitat units comprising the salt marsh ecosystem.

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Section: Limitations Of the Modelssupporting

confidence: 66%

Section: Ecohydrological Zonationmentioning

confidence: 99%

Section: Surface Boundary Conditions: Evapotranspiration Scenariosmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Salt marsh ecohydrological zonation due to heterogeneous vegetation–groundwater–surface water interactions

Moffett¹,

Gorelick²,

McLaren³

et al. 2012

Water Resources Research

112

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Plant‐soil interactions in salt marsh environments: Experimental evidence from electrical resistivity tomography in the Venice Lagoon

Boaga

D’Alpaos

Cassiani

et al. 2014

Geophysical Research Letters

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The role of root water uptake in regulating soil water saturation in salt marshes is controversial.Modeling studies suggest that soil aeration is improved by transpiration, with implications for the distribution of vegetation species and of the associated topographic features controlling the hydraulic regime of the marshland and eventually its survival. Marsh vegetation plays a key role in the preservation of such critical environment, which represents unique marker for climatic change and impact studies. However, the direct quantification of space-time aeration patterns has remained elusive, in part, because of the limitations posed by high salinity to conventional observation techniques such as time or frequency domain reflectometry. Here we show that time-lapse microscale electrical resistivity tomography, coupled with tensiometric observations, allows the identification of variably saturated zones and the characterization of space-time soil moisture dynamics in a salt marsh in the Venice Lagoon (Italy). This is the first quantitative observational experiment which confirms that periodically flooded plants are capable of producing a persistently aerated layer below the flooded surface when transpiration proceeds at a sufficiently high rate. The experimental results are compared against previously published model predictions.

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Relating salt marsh pore water geochemistry patterns to vegetation zones and hydrologic influences

Moffett

Gorelick

2016

Water Resources Research

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Physical, chemical, and biological factors influence vegetation zonation in salt marshes and other wetlands, but connections among these factors could be better understood. If salt marsh vegetation and marsh pore water geochemistry coorganize, e.g., via continuous plant water uptake and persistently unsaturated sediments controlling vegetation zone-specific pore water geochemistry, this could complement known physical mechanisms of marsh self-organization. A high-resolution survey of pore water geochemistry was conducted among five salt marsh vegetation zones at the same intertidal elevation. Sampling transects were arrayed both parallel and perpendicular to tidal channels. Pore water geochemistry patterns were both horizontally differentiated, corresponding to vegetation zonation, and vertically differentiated, relating to root influences. The geochemical patterns across the site were less broadly related to marsh hydrology than to vegetation zonation. Mechanisms contributing to geochemical differentiation included: root-induced oxidation and nutrient (P) depletion, surface and creek-bank sediment flushing by rainfall or tides, evapotranspiration creating aerated pore space for partial sediment flushing in some areas while persistently saturated conditions hindered pore water renewal in others, and evapoconcentration of pore water solutes overall. The concentrated pore waters draining to the tidal creeks accounted for 41% of ebb tide solutes (median of 14 elements), including being a potentially toxic source of Ni but a slight sink for Zn, at least during the short, winter study period in southern San Francisco Bay. Heterogeneous vegetation effects on pore water geochemistry are not only significant locally within the marsh but may broadly influence marsh-estuary solute exchange and ecology.

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Water Uptake by Roots Controls Water Table Movement and Sediment Oxidation in Short Spartina Marsh

Cited by 171 publications

References 22 publications

Salt marsh ecohydrological zonation due to heterogeneous vegetation–groundwater–surface water interactions

Salt marsh ecohydrological zonation due to heterogeneous vegetation–groundwater–surface water interactions

Plant‐soil interactions in salt marsh environments: Experimental evidence from electrical resistivity tomography in the Venice Lagoon

Relating salt marsh pore water geochemistry patterns to vegetation zones and hydrologic influences

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