title: Drought-induced xylem cavitation and hydraulic deterioration: risk factors for urban trees under climate change?
abstract: Urban trees help towns to cope with climate warming by cooling both air and surfaces. The challenges imposed by the urban environment, with special reference to low water availability due to the presence of extensive pavements, result in high rates of mortality of street trees, that can be increased by climatic extremes. We investigated the water relations and xylem hydraulic safety/efficiency of Quercus ilex trees growing at urban sites with different percentages of surrounding impervious pavements. Seasonal changes of plant water potential and gas exchange, vulnerability to cavitation and embolism level, and morpho-anatomical traits were measured. We found patterns of increasing water stress and vulnerability to drought at increasing percentages of impervious pavement cover, with a consequent reduction in gas exchange rates, decreased safety margins toward embolism development, and increased vulnerability to cavitation, suggesting the occurrence of stress-induced hydraulic deterioration. The amount of impermeable surface and chronic exposure to water stress influence the site-specific risk of drought-induced dieback of urban trees under extreme drought. Besides providing directions for management of green spaces in towns, our data suggest that xylem hydraulics is key to a full understanding of the responses of urban trees to global change.
authors.affiliation: Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, Trieste, 34127, Italy.
authors.forename: Tadeja
authors.initials: T
authors.lastname: Savi
authors.affiliation: Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, Trieste, 34127, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Bertuzzi
authors.affiliation: Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, Trieste, 34127, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Branca
authors.affiliation: Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, Trieste, 34127, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Tretiach
authors.affiliation: Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, Trieste, 34127, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Nardini
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D002947:Cities; D057231:Climate Change; D055864:Droughts; D005453:Fluorescence; D005740:Gases / Q000378:metabolism; D007558:Italy; D010788:Photosynthesis; D018515:Plant Leaves / Q000502:physiology; D018547:Plant Stems / Q000502:physiology; D029963:Quercus / Q000502:physiology*; D012307:Risk Factors; D012621:Seasons; D012987:Soil; D013227:Steam; D014197:Trees / Q000502:physiology*; D014867:Water / Q000502:physiology*; D014934:Wood; D052584:Xylem / Q000502:physiology*
chemical_list: D005740:Gases; D012987:Soil; D013227:Steam; D014867:Water; D002734:Chlorophyll
keywords: Quercus ilex; climate change; dieback; embolism; hydraulic deterioration; towns; urban trees; xylem vulnerability