title: Rooting depth, water relations and non-structural carbohydrate dynamics in three woody angiosperms differentially affected by an extreme summer drought.
abstract: In 2012, an extreme summer drought induced species-specific die-back in woody species in Northeastern Italy. Quercus pubescens and Ostrya carpinifolia were heavily impacted, while Prunus mahaleb was largely unaffected. By comparing seasonal changes in isotopic composition of xylem sap, rainfall and deep soil samples, we show that P. mahaleb has a deeper root system than the other two species. This morphological trait allowed P  mahaleb to maintain higher water potential (Ψ), gas exchange rates and non-structural carbohydrates content (NSC) throughout the summer, when compared with the other species. More favourable water and carbon states allowed relatively stable maintenance of stem hydraulic conductivity (k) throughout the growing season. In contrast, in Quercus pubescens and Ostrya carpinifolia, decreasing Ψ and NSC were associated with significant hydraulic failure, with spring-to-summer k loss averaging 60%. Our data support the hypothesis that drought-induced tree decline is a complex phenomenon that cannot be modelled on the basis of single predictors of tree status like hydraulic efficiency, vulnerability and carbohydrate content. Our data highlight the role of rooting depth in seasonal progression of water status, gas exchange and NSC, with possible consequences for energy-demanding mechanisms involved in the maintenance of vascular integrity.
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
authors.affiliation: Dipartimento di Scienze Agrarie e Ambientali, Università di Udine, Sezione di Biologia Vegetale, Via delle Scienze 91, Udine, 33100, Italy.
authors.forename: Valentino
authors.initials: V
authors.lastname: Casolo
authors.affiliation: Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, Trieste, 34127, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Dal Borgo
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 Ambientali, Informatica e Statistica, Università Ca' Foscari Venezia, via Torino 155, Venezia Mestre, 30170, Italy.|Dipartimento di Matematica e Geoscienze, Università di Trieste, Via Weiss 2, Trieste, 34127, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Stenni
authors.affiliation: Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, Trieste, 34127, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Bertoncin
authors.affiliation: Dipartimento di Matematica e Geoscienze, Università di Trieste, Via Weiss 2, Trieste, 34127, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Zini
authors.affiliation: Los Alamos National Laboratory, Earth and Environmental Sciences Division, Los Alamos, NM, 87545, USA.
authors.forename: Nathan G
authors.initials: NG
authors.lastname: McDowell
mesh_terms: D002241:Carbohydrates / Q000737:chemistry*; D059552:Caves; D055864:Droughts; D005740:Gases / Q000378:metabolism; D019684:Magnoliopsida / Q000378:metabolism / Q000502:physiology*; D010103:Oxygen Isotopes; D018515:Plant Leaves / Q000502:physiology; D018517:Plant Roots / Q000502:physiology*; D018547:Plant Stems / Q000502:physiology; D011891:Rain; D012621:Seasons; D012987:Soil / Q000737:chemistry; D013213:Starch / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism; D013696:Temperature; D014867:Water / Q000502:physiology*; D014934:Wood / Q000502:physiology*; D052584:Xylem / Q000737:chemistry
chemical_list: D002241:Carbohydrates; D005740:Gases; D010103:Oxygen Isotopes; D012987:Soil; D014867:Water; D013395:Sucrose; D013213:Starch
keywords: cave; isotopes; rainfall; soil; xylem hydraulics; xylem sap