title: A 6-Year-Long Manipulation with Soil Warming and Canopy Nitrogen Additions does not Affect Xylem Phenology and Cell Production of Mature Black Spruce.
abstract: The predicted climate warming and increased atmospheric inorganic nitrogen deposition are expected to have dramatic impacts on plant growth. However, the extent of these effects and their interactions remains unclear for boreal forest trees. The aim of this experiment was to investigate the effects of increased soil temperature and nitrogen (N) depositions on stem intra-annual growth of two mature stands of black spruce [Picea mariana (Mill.) BSP] in Québec, QC, Canada. During 2008-2013, the soil around mature trees was warmed up by 4°C with heating cables during the growing season and precipitations containing three times the current inorganic N concentration were added by frequent canopy applications. Xylem phenology and cell production were monitored weekly from April to October. The 6-year-long experiment performed in two sites at different altitude showed no substantial effect of warming and N-depositions on xylem phenological phases of cell enlargement, wall thickening and lignification. Cell production, in terms of number of tracheids along the radius, also did not differ significantly and followed the same patterns in control and treated trees. These findings allowed the hypothesis of a medium-term effect of soil warming and N depositions on the growth of mature black spruce to be rejected.
authors.affiliation: Département Productions Forestières, Institut de l'Environnement et de Recherches Agricoles Ouagadougou, Burkina Faso.
authors.forename: Madjelia C E
authors.initials: MC
authors.lastname: Dao
authors.affiliation: Département des Sciences Fondamentales, Université du Québec à Chicoutimi Chicoutimi, QC, Canada.
authors.forename: Sergio
authors.initials: S
authors.lastname: Rossi
authors.affiliation: Département des Sciences Fondamentales, Université du Québec à Chicoutimi Chicoutimi, QC, Canada.
authors.forename: Denis
authors.initials: D
authors.lastname: Walsh
authors.affiliation: Département des Sciences Fondamentales, Université du Québec à Chicoutimi Chicoutimi, QC, Canada.
authors.forename: Hubert
authors.initials: H
authors.lastname: Morin
authors.affiliation: Direction de la Recherche Forestière, Forêt Québec, Ministère des Forêts de la Faune et des Parcs Québec, QC, Canada ; Ouranos, Consortium Sur la Climatologie Régionale et l'Adaptation aux Changements Climatiques Montréal, QC, Canada.
authors.forename: Daniel
authors.initials: D
authors.lastname: Houle
keywords: N deposition; boreal forest; cambial activity; climate change; increased soil temperature; intra-annual growth; wood anatomy; xylogenesis