Hydraulic vulnerability of native trees is increased by urban heat
Start Date
2-11-2019 1:50 PM
End Date
2-11-2019 2:00 PM
Abstract
While a warming climate has implications on human populations and infrastructure systems, we also need a better understanding of ecosystem responses, particularly within urban landscapes. Since cities amplify temperatures through a phenomenon known as the ‘urban heat island effect,’ we can examine variation in temperature-related stress to assess the response of urban ecological systems. Here we combined a highly-resolved urban heat map and tree canopy data with plant ecophysiological techniques to ask 3 research questions: 1) how does variation in urban temperatures impact hydraulic function of native Northwest trees?; 2) what is the water status of trees exposed to different levels of urban heat?; and 3) which native tree species are most at risk during a warming climate? We address these questions by examining three PNW native tree species: Douglas-fir (Pseudotsuga menziesii), western redcedar (Thuja plicata), and bigleaf maple (Acer macrophyllum) across an urban heat gradient in the City of Portland. Our findings suggest trees in warm sites have lower water status, elevated rates of hydraulic impairment, and other indicators of temperature and moisture stress. Consistent patterns of difference across species with contrasting water use strategies (e.g., conifers vs. angiosperms) suggests urban heat affects a wide variety of plant functional types. Highest rates of loss in hydraulic conductivity in bigleaf maple--which composes approximately 20% of the urban canopy--suggests this species may be particularly vulnerable to future drought/heat stress in Portland, and in western Oregon as a whole as temperatures continue to rise.
Subjects
Climate Change, Plant ecology
Persistent Identifier
https://archives.pdx.edu/ds/psu/33808
Rights
© Copyright the author(s)
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Hydraulic vulnerability of native trees is increased by urban heat
While a warming climate has implications on human populations and infrastructure systems, we also need a better understanding of ecosystem responses, particularly within urban landscapes. Since cities amplify temperatures through a phenomenon known as the ‘urban heat island effect,’ we can examine variation in temperature-related stress to assess the response of urban ecological systems. Here we combined a highly-resolved urban heat map and tree canopy data with plant ecophysiological techniques to ask 3 research questions: 1) how does variation in urban temperatures impact hydraulic function of native Northwest trees?; 2) what is the water status of trees exposed to different levels of urban heat?; and 3) which native tree species are most at risk during a warming climate? We address these questions by examining three PNW native tree species: Douglas-fir (Pseudotsuga menziesii), western redcedar (Thuja plicata), and bigleaf maple (Acer macrophyllum) across an urban heat gradient in the City of Portland. Our findings suggest trees in warm sites have lower water status, elevated rates of hydraulic impairment, and other indicators of temperature and moisture stress. Consistent patterns of difference across species with contrasting water use strategies (e.g., conifers vs. angiosperms) suggests urban heat affects a wide variety of plant functional types. Highest rates of loss in hydraulic conductivity in bigleaf maple--which composes approximately 20% of the urban canopy--suggests this species may be particularly vulnerable to future drought/heat stress in Portland, and in western Oregon as a whole as temperatures continue to rise.