Browsing by Author "Apisa, Ethan"

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    Tree Performance in a Gravel Bed Bioretention System
    Apisa, Ethan; Wiseman, P. Eric (2021-11-05)
    Stormwater runoff is an issue in urban areas as impervious surfaces increase. Various retention systems that incorporate trees have been developed but are expensive and require large amounts of space and cause their implementation to be difficult. We are investigating a system that is simple and mitigates the effects of stormwater runoff while increasing the urban tree canopy. Our full-scale prototype of this system has been constructed adjacent to a parking lot on Virginia Tech’s campus in Blacksburg, VA. It consists of a rectangular prism of a clay loam soil surrounded by a gravel moat filled with gravel. The system mitigates stormwater runoff by utilizing water uptake from three London planetrees planted in the soil prism. The gravel bed is intended to support an expansive root system that can absorb and transpire captured runoff while utilizing the soil for nutrients and anchorage. Adjacent to the gravel bed are three control trees of the same species, planted in the undisturbed native soil. The purpose of this study is to evaluate and compare tree performance and characterize the hydrology of the gravel bed. We are monitoring crown and root growth, photosynthesis, conductance rates, plant-water relations, and rainfall. The trees in the system have generally outperformed the control since being planted in May 2020.
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    Tree Performance in a Stormwater Bioretention System
    Apisa, Ethan; Wiseman, P. Eric (2022-01-25)
    Stormwater runoff from impervious surfaces in urban areas causes water pollution and flash flooding. Trees can help solve this problem by capturing and absorbing rain. However, there is often not enough space in cities for both trees and conventional stormwater control systems. Various bioretention systems that incorporate trees are used in cities, but they are expensive and complex, which makes their implementation difficult. We are investigating a system that may prove to be less complex, less costly, and better for growing trees. Our full-scale prototype of this system was constructed in 2020 adjacent to a parking lot on the Virginia Tech campus in Blacksburg, VA. It comprises a belowground gravel bed surrounding a soil bed where trees are planted. The gravel bed stores a large volume of parking lot runoff that is then absorbed by the tree roots and expelled to the air through transpiration. Our long-term study of this prototype aims to understand how well the system captures and stores runoff and how well the trees perform compared to control trees in a standard planting nearby. We are monitoring tree crown and root growth, photosynthesis, and leaf stomatal conductance. Growth and physiology of the trees in the system has been comparable to the control trees since being planted in May 2020.