title: Functional adjustments of xylem anatomy to climatic variability: insights from long-term Ilex aquifolium tree-ring series.
abstract: The present study assessed the effects of climatic conditions on radial growth and functional anatomical traits, including ring width, vessel size, vessel frequency and derived variables, i.e., potential hydraulic conductivity and xylem vulnerability to cavitation in Ilex aquifolium L. trees using long-term tree-ring time series obtained at two climatically contrasting sites, one mesic site in Switzerland (CH) and one drought-prone site in Italy (ITA). Relationships were explored by examining different xylem traits, and point pattern analysis was applied to investigate vessel clustering. We also used generalized additive models and bootstrap correlation functions to describe temperature and precipitation effects. Results indicated modified radial growth and xylem anatomy in trees over the last century; in particular, vessel frequency increased markedly at both sites in recent years, and all xylem traits examined, with the exception of xylem cavitation vulnerability, were higher at the CH mesic compared with the ITA drought site. A significant vessel clustering was observed at the ITA site, which could contribute to an enhanced tolerance to drought-induced embolism. Flat and negative relationships between vessel size and ring width were observed, suggesting carbon was not allocated to radial growth under conditions which favored stem water conduction. Finally, in most cases results indicated that climatic conditions influenced functional anatomical traits more substantially than tree radial growth, suggesting a crucial role of functional xylem anatomy in plant acclimation to future climatic conditions.
authors.affiliation: Scuola di Scienze Agrarie, Forestali, Alimentari e Ambientali, Università della Basilicata, Viale dell'Ateneo Lucano 10, 85100 Potenza, Italy angelo.rita@unibas.it.
authors.forename: Angelo
authors.initials: A
authors.lastname: Rita
authors.affiliation: WSL Swiss Federal Research Institute, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.
authors.forename: Paolo
authors.initials: P
authors.lastname: Cherubini
authors.affiliation: Dipartimento di Bioscienze, Università di Parma, viale Usberti 11, 43100 Parma, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Leonardi
authors.affiliation: Scuola di Scienze Agrarie, Forestali, Alimentari e Ambientali, Università della Basilicata, Viale dell'Ateneo Lucano 10, 85100 Potenza, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Todaro
authors.affiliation: Scuola di Scienze Agrarie, Forestali, Alimentari e Ambientali, Università della Basilicata, Viale dell'Ateneo Lucano 10, 85100 Potenza, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Borghetti
mesh_terms: D000064:Acclimatization; D002244:Carbon / Q000378:metabolism; D002980:Climate; D055864:Droughts; D030017:Ilex / Q000033:anatomy & histology* / Q000502:physiology; D018547:Plant Stems / Q000033:anatomy & histology / Q000502:physiology; D011891:Rain; D013696:Temperature; D014197:Trees; D014867:Water / Q000502:physiology; D052584:Xylem / Q000033:anatomy & histology* / Q000502:physiology
chemical_list: D014867:Water; D002244:Carbon
keywords: European holly; precipitation; ring width; temperature; vessel characteristics; wood anatomy