title: Soil surface temperatures reveal moderation of the urban heat island effect by trees and shrubs.
abstract: Urban areas are major contributors to air pollution and climate change, causing impacts on human health that are amplified by the microclimatological effects of buildings and grey infrastructure through the urban heat island (UHI) effect. Urban greenspaces may be important in reducing surface temperature extremes, but their effects have not been investigated at a city-wide scale. Across a mid-sized UK city we buried temperature loggers at the surface of greenspace soils at 100 sites, stratified by proximity to city centre, vegetation cover and land-use. Mean daily soil surface temperature over 11 months increased by 0.6 °C over the 5 km from the city outskirts to the centre. Trees and shrubs in non-domestic greenspace reduced mean maximum daily soil surface temperatures in the summer by 5.7 °C compared to herbaceous vegetation, but tended to maintain slightly higher temperatures in winter. Trees in domestic gardens, which tend to be smaller, were less effective at reducing summer soil surface temperatures. Our findings reveal that the UHI effects soil temperatures at a city-wide scale, and that in their moderating urban soil surface temperature extremes, trees and shrubs may help to reduce the adverse impacts of urbanization on microclimate, soil processes and human health.
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, U.K.
authors.forename: J L
authors.initials: JL
authors.lastname: Edmondson
authors.affiliation: Max-Planck Odense Center, Department of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark.
authors.forename: I
authors.initials: I
authors.lastname: Stott
authors.affiliation: Durrell Institute of Conservation and Ecology (DICE), School of Anthropology and Conservation, University of Kent, Canterbury, Kent CT2 7NR, UK.
authors.forename: Z G
authors.initials: ZG
authors.lastname: Davies
authors.affiliation: Environment and Sustainability Institute, University of Exeter, Penryn, Cornwall TR10 9FE, U.K.
authors.forename: K J
authors.initials: KJ
authors.lastname: Gaston
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, U.K.
authors.forename: J R
authors.initials: JR
authors.lastname: Leake
mesh_terms: D002947:Cities; D002980:Climate; D004784:Environmental Monitoring; D006358:Hot Temperature; D006801:Humans; D012621:Seasons; D012987:Soil; D013696:Temperature; D014197:Trees
chemical_list: D012987:Soil