Water relations of street trees in green infrastructure tree trench systems

Caplan, Joshua S.; Galanti, Russell C.; Olshevski, Stuart; Eisenman, Sasha W.

doi:10.1016/j.ufug.2019.03.016

Cited by 35 publications

(25 citation statements)

References 38 publications

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“…Runoff entering the bottom of the infiltration bed was intended to rise to the level of the soil pits such that it would provide water to the trees. Additional information about the site and tree trench system can be found in earlier works involving this system [24,25].…”

Section: Site Descriptionmentioning

confidence: 99%

“…Procedures for data collection are described in detail elsewhere [25], but briefly, Ψ md and g s were measured in each of the five trees between 1100-1300 h, 1-2 times per week from May through October. A leaf porometer (SC-1, METER Environment, Pullman, USA) was used to measure g s and a Scholander-type pressure chamber (PMS Instruments, Albany, USA) was used to measure Ψ md .…”

Section: Plant Water Stressmentioning

confidence: 99%

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When Green Infrastructure Turns Grey: Plant Water Stress as a Consequence of Overdesign in a Tree Trench System

Caplan

Eisenman

et al. 2020

Water

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Green infrastructure (GI) systems are often overdesigned. This may be a byproduct of static sizing (e.g., accounting for a design storm’s runoff volume but not exfiltration rates) or may be deliberate (e.g., buffering against performance loss through time). In tree trenches and other GI systems that require stormwater to accumulate in an infiltration bed before it contacts the planting medium, overdesign could reduce plant water availability significantly. This study investigated the hydrological dynamics and water relations of an overdesigned tree trench system and identified factors contributing to, compounding, and mitigating the risk of plant stress. Water in the infiltration bed reached soil pits only once in three years, with that event occurring during a hydrant release. Moreover, minimal water was retained in soil pits during the event due to the hydraulic properties of the soil media. Through a growing season, one of the two tree types frequently experienced water stress, while the other did so only rarely. These contrasting responses can likely be attributed to roots being largely confined to the soil pits vs. reaching a deeper water source, respectively. Results of this study demonstrate that, in systems where soil pits are embedded in infiltration beds, overdesign can raise the storm size required for water to reach the soil media, reducing plant water availability between storms, and ultimately inducing physiological stress.

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Section: Site Descriptionmentioning

confidence: 99%

Section: Plant Water Stressmentioning

confidence: 99%

When Green Infrastructure Turns Grey: Plant Water Stress as a Consequence of Overdesign in a Tree Trench System

Caplan

Eisenman

et al. 2020

Water

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View full text Add to dashboard Cite

show abstract

Section: Site Descriptionmentioning

confidence: 99%

“…Procedures for data collection are described in detail elsewhere [25] but briefly, md and gs were measured in each of the five trees between 1100-1300 h, 1-2 times per week from May through October. A leaf porometer (SC-1, METER Environment, Pullman, USA) was used to measure gs and a Scholander-type pressure chamber (PMS Instruments, Albany, USA) was used to measure md.…”

Section: Plant Water Stressmentioning

confidence: 99%

When Green Infrastructure Turns Grey: Implications of Overdesign on Plant Water Stress

Tu¹,

Caplan²,

Eisenman³

et al. 2020

Preprint

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Green infrastructure systems are often overdesigned. This may be a byproduct of static sizing (e.g., accounting for a design storm’s runoff volume but not exfiltration rates) or may be deliberate (e.g., buffering against performance loss through time). Regardless, overdesign may compromise plants’ access to water in systems where soil pits are embedded in infiltration beds. It could raise the storm size required for water to reach soil pits, reducing water availability between storms, which could ultimately induce plant physiological stress. This study investigated the hydrological dynamics and water relations of a tree trench system suspected to have been overbuilt and identified factors contributing to, compounding, and mitigating the risk of plant stress. Results provided strong evidence that the abovementioned processes played out. Water in the infiltration bed reached soil pits only once in three years, with that event occurring during a hydrant release. Moreover, minimal water was retained in the soil pit during the event due to the hydraulic properties of the soil media. Through a growing season, one of the two tree types frequently experienced water stress, while the other did so only rarely. These contrasting responses can likely be attributed to roots either being largely confined to the soil pits or reaching a deeper water source. Implications of these results for green infrastructure design are considered.

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“…Overdesign is generally considered benign to stormwater control performance and is sometimes even favored (Vrban et al 2018). However, there is mounting evidence that overdesign can have negative implications for plant water availability in systems designed to use stormwater as a primary water source for vegetation (Brown et al 2015, Caplan et al 2019. For plants that are unable to reach alternative water sources, overdesign may increase the frequency, intensity, and duration of plant water stress events, ultimately reducing transpiration rates and diminishing the associated benefits.…”

Section: Introductionmentioning

confidence: 99%

When Green Infrastructure Turns Grey: Implications of Overdesign for Plant Water Stress

Tu¹,

Caplan²,

Eisenman³

et al. 2019

Preprint

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Overdesign is a common strategy used by green infrastructure (GI) designers to account for unexpected performance loss, but such a strategy can create undesirable plant responses if it decreases water availability. The seasonal and event-based stomatal conductance data of two woody plant species in a green infrastructure (GI) was analyzed. The GI is a tree trench composed of five tree pits (each one was planted with a tree) in an infiltration bed. Runoff collected from the street was supplied to the bottom of the infiltration bed, although the system never filled completely indicating there was capacity for more runoff than what was observed over 3 years and the infiltration bed was overdesigned. Between the two tree species, evidence suggested that the root system of London plane spread beyond the boundary of the GI system and reached a subsurface water source, while that of hybrid maple did not. London plane showed a slower response to water added in the tree pit soil, which can indicate the reduced dependence on GI soil water after plants have reached an alternative water source. Such reduction is not favored because it defeats the purpose of having plants in GI systems. Designs using root barriers, appropriate plant species selection, etc. are recommended to avoid unwanted root spread. This study also found that GI design relying on upward water movements should be avoided because such design creates a narrow capillary zone on top of a saturated zone, which does not encourage transpiration.

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Water relations of street trees in green infrastructure tree trench systems

Cited by 35 publications

References 38 publications

When Green Infrastructure Turns Grey: Plant Water Stress as a Consequence of Overdesign in a Tree Trench System

When Green Infrastructure Turns Grey: Plant Water Stress as a Consequence of Overdesign in a Tree Trench System

When Green Infrastructure Turns Grey: Implications of Overdesign on Plant Water Stress

When Green Infrastructure Turns Grey: Implications of Overdesign for Plant Water Stress

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