title: How do drought and warming influence survival and wood traits of Picea mariana saplings?
abstract: Warming and drought will occur with increased frequency and intensity at high latitudes in the future. How heat and water stress can influence tree mortality is incompletely understood. The aim of this study was to evaluate how carbon resources, stem hydraulics, and wood anatomy and density determine the ability of black spruce saplings to survive daytime or night-time warming (+ 6 °C in comparison with control) in combination with a drought period. Plant water relations, the dynamics of non-structural carbohydrates and starch, mortality rate, and wood anatomy and density of saplings were monitored. Warming, in conjunction with 25 d of water deficit, increased sapling mortality (10% and 20% in night-time and daytime warming, respectively) compared with the control conditions (0.8%). Drought substantially decreased gas exchange, and also pre-dawn and mid-day leaf water potential to values close to -3MPa which probably induced xylem embolism (xylem air entry point, P₁₂, being on average around -3MPa for this species). In addition, the recovery of gas exchange never reached the initial pre-stress levels, suggesting a possible loss of xylem hydraulic conductivity associated with cavitation. Consequently, mortality may be due to xylem hydraulic failure. Warmer temperatures limited the replenishment of starch reserves after their seasonal minimum. Lighter wood was formed during the drought period, reflecting a lower carbon allocation to cell wall formation, preventing the adaptation of the hydraulic system to drought. Saplings of black spruce experienced difficulty in adapting under climate change conditions, which might compromise their survival in the future.
authors.affiliation: Département des Sciences Fondamentales, Université du Québec à Chicoutimi, 555 boulevard de l'Université, Chicoutimi, QC G7H2B1, Canada lorena.balducci1@uqac.ca.
authors.forename: Lorena
authors.initials: L
authors.lastname: Balducci
authors.affiliation: Département des Sciences Fondamentales, Université du Québec à Chicoutimi, 555 boulevard de l'Université, Chicoutimi, QC G7H2B1, Canada.
authors.forename: Annie
authors.initials: A
authors.lastname: Deslauriers
authors.affiliation: CNR-IVALSA, Via Madonna de Piano, 50019 Sesto Fiorentino, (FI), Italy.
authors.forename: Alessio
authors.initials: A
authors.lastname: Giovannelli
authors.affiliation: Département des Sciences Fondamentales, Université du Québec à Chicoutimi, 555 boulevard de l'Université, Chicoutimi, QC G7H2B1, Canada.
authors.forename: Marilène
authors.initials: M
authors.lastname: Beaulieu
authors.affiliation: INRA-University of Bordeaux, UMR BIOGECO, Bat-B2, Avenue des Facultés, 33405 Talence-France.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Delzon
authors.affiliation: Département des Sciences Fondamentales, Université du Québec à Chicoutimi, 555 boulevard de l'Université, Chicoutimi, QC G7H2B1, Canada.
authors.forename: Sergio
authors.initials: S
authors.lastname: Rossi
authors.affiliation: INRA, UMR1092 LERFoB, F-54280 Champenoux, France.
authors.forename: Cyrille B K
authors.initials: CB
authors.lastname: Rathgeber
mesh_terms: D000222:Adaptation, Physiological; D050260:Carbohydrate Metabolism; D057231:Climate Change; D055864:Droughts; D028222:Picea / Q000033:anatomy & histology* / Q000254:growth & development*; D018547:Plant Stems / Q000378:metabolism; D013213:Starch / Q000378:metabolism; D014867:Water / Q000378:metabolism; D014934:Wood / Q000033:anatomy & histology / Q000502:physiology*
chemical_list: D014867:Water; D013213:Starch
keywords: Carbon balance; climate change; drought; survival; warming; wood anatomy; wood density.