Skip to main content
2023 ESA Annual Meeting Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.
Back

Contributed Poster

Session: Ecosystem Stability And Resilience

PS 25-84 - Hiding in plain sight: Validation of an urban climate refugium for Thuja plicata (western redcedar) in Portland, OR

Tuesday, August 8, 2023
5:00 PM – 6:30 PM PDT
Location: ESA Exhibit Hall
Abstract:
Increased temperatures and drought are driving elevated rates of tree mortality globally and increasingly in the carbon dense conifer forests of the Pacific Northwest. However, climate change impacts on forest trees may be less pronounced in sites with persistent water supplies, i.e. hydrologic refugia. Within the American Pacific Northwest, western redcedar (Thuja plicata) is a culturally and economically important species that has experienced recent dieback due to exacerbated drought and heat stress and may be especially vulnerable in warm, dry urban sites that are subject to the urban heat island effect. The extent to which potential hydrologic refugia in urban environments, such as local urban wetland and riparian habitats, might be able to protect T. plicata from worsening regional drought conditions and heat waves has yet to be evaluated. I investigated an urban wetland/riparian natural area as a potential hydrologic refugium for T. plicata on the campus of Reed College, in Portland, OR. The small forested natural area (i.e. the Reed Canyon) is perennially fed by a large natural spring and sits in a local topographic depression, both features of hydrologic refugia in other systems. To see if T. plicata trees in this relatively mesic habitat were buffered from regional drought conditions, we compared predawn and midday leaf water potential (Ψw), CO2 assimilation (A) and temperature optimum from Reed Canyon's trees to those in warmer, drier urban sites, as well as rural forested areas (i.e. outside the urban heat island effect). We found that T. plicata trees in the Reed Canyon exhibit a level of tissue water status (Ψw) and photosynthetic activity (A) that are more similar to rural trees than to those in other urban sites. This suggests that the trees in the Reed Canyon may have increased access to soil moisture, reduced stress, and mortality risk from regional drought conditions, despite exposure to the urban heat island effect. This also suggests that trees in the Reed Canyon may be better able to persist under worsening regional drought conditions, compared to other urban trees.