319: Tree Health, Growth and Cooling Effects at Contrasting Urban Sites in Gothenburg, Sweden

• One of the most important ecosystem services provided by urban trees is the mitigation of urban heat. However, this cooling effect may be compromised due to vulnerability of urban trees to harsh urban environment and ongoing climate change. In this project we aim to analyse the growth and health of urban tree species in Gothenburg, Sweden in response to different urban growing conditions, as well as the impact of heat and drought stress on tree cooling benefits through changes to shading effect and transpiration. Three species with different adaptation mechanisms to drought stress were selected: Aesculus hippocastanum, Tilia europaea and Quercus palustris. For each species, trees of the same age planted at adjacent paved and unpaved sites were chosen for the study. In 2017, measured traits included stomatal conductance and transpiration rates, pre-dawn and midday water potentials, chlorophyll content, and leaf area density. In 2018, additional microclimate and human thermal comfort measurements were added to assess the cooling benefits provided by trees. The summertime measurements in 2017 showed significant differences in multiple plant traits between contrasting sites for all species studied, with trees at paved sites showing reduced gas exchange, chlorophyll content and leaf area density compared to sites with a higher fraction of permeable surfaces. These differences were observed both on a hot summer day following a dry period, as well as on a cooler day following a wet period. A clear difference in water use dynamics between species with ”tolerant” (e.g. Q. palustris) and ”avoiding” (e.g. A. hippocastanum) mechanisms against drought stress were also observed. The results highlight the importance of proper planning and species selection in supporting the health and resilience of the urban forest as well as maximising its cooling benefits. The study will be continued in Melbourne, Australia with the focus on urban tree performance alongside water sensitive urban design (WSUD).

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Environmental Sciences (hsv//eng)

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Meteorologi och atmosfärforskning (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Meteorology and Atmospheric Sciences (hsv//eng)

NATURVETENSKAP  -- Biologi -- Botanik (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Botany (hsv//eng)

Nyckelord

Urban vegetation

street trees

outdoor thermal comfort

tree physiology

cooling effect

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