title: Adjustment capacity of maritime pine cambial activity in drought-prone environments.
abstract: Intra-annual density fluctuations (IADFs) are anatomical features formed in response to changes in the environmental conditions within the growing season. These anatomical features are commonly observed in Mediterranean pines, being more frequent in younger and wider tree rings. However, the process behind IADF formation is still unknown. Weekly monitoring of cambial activity and wood formation would fill this void. Although studies describing cambial activity and wood formation have become frequent, this knowledge is still fragmentary in the Mediterranean region. Here we present data from the monitoring of cambial activity and wood formation in two diameter classes of maritime pine (Pinus pinaster Ait.), over two years, in order to test: (i) whether the differences in stem diameter in an even-aged stand were due to timings and/or rates of xylogenesis; (ii) if IADFs were more common in large trees; and (iii) if their formation is triggered by cambial resumption after the summer drought. Larger trees showed higher rates of cell production and longer growing seasons, due to an earlier start and later end of xylogenesis. When a drier winter occurs, larger trees were more affected, probably limiting xylogenesis in the summer months. In both diameter classes a latewood IADF was formed in 2012 in response to late-September precipitation, confirming that the timing of the precipitation event after the summer drought is crucial in determining the resumption of cambial activity and whether or not an IADF is formed. It was the first time that the formation of a latewood IADF was monitored at a weekly time scale in maritime pine. The capacity of maritime pine to adjust cambial activity to the current environmental conditions represents a valuable strategy under the future climate change conditions.
authors.affiliation: CFE - Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal.
authors.forename: Joana
authors.initials: J
authors.lastname: Vieira
authors.affiliation: CFE - Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal.
authors.forename: Filipe
authors.initials: F
authors.lastname: Campelo
authors.affiliation: Département des Sciences Fondamentales, Université du Québec à Chicoutimi, Chicoutimi, Canada; Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, Provincial Key Laboratory of Applied Botany South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.
authors.forename: Sergio
authors.initials: S
authors.lastname: Rossi
authors.affiliation: CFE - Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Carvalho
authors.affiliation: CFE - Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal.
authors.forename: Helena
authors.initials: H
authors.lastname: Freitas
authors.affiliation: CFE - Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal.
authors.forename: Cristina
authors.initials: C
authors.lastname: Nabais
mesh_terms: D055864:Droughts; D028223:Pinus / Q000502:physiology*; D012621:Seasons