Canadian Forest Service Publications

Changes in specific leaf area and photosynthetic nitrogen-use efficiency associated with physiological acclimation of two hybrid poplar clones to intraclonal competition. 2011. Benomar, L.; DesRochers, A.; Larocque, G.R. Can. J. For. Res. 41: 1465-1476.

Year: 2011

Issued by: Laurentian Forestry Centre

Catalog ID: 39595

Language: English

Availability: PDF (request by e-mail)

Available from the Journal's Web site. †
DOI: 10.1139/x11-073

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Abstract

Photosynthesis is the most important process driving productivity, and its acclimation to intraclonal competition is not well understood in hybrid poplars. The aim of this study was to examine the physiological response of the crown of two hybrid poplar clones, BT747215 (Populus balsamifera L. × Populus trichocarpa Torr. & A. Gray) and MB915319 (Populus maximowiczii A. Henry × P. balsamifera), to intraclonal competition. We measured light-saturated photosynthesis (A_max), leaf N content on an area basis (N_area), specific leaf area (SLA), and photosynthetic N-use efficiency (PNUE) for three successive growing seasons on trees planted at three spacings (1 m × 1 m, 3 m × 3 m, and 5 m × 5 m). Crowns were sampled at 10 locations corresponding to vertical and horizontal subdivisions. Significant changes took place at the crown level in the closest spacing (1 m × 1 m) compared with the wider spacings (3 m × 3 m and 5 m × 5 m): (i) 30% decrease in N_area, (ii) 20% increase in SLA, and (iii) 40% increase in PNUE. The slope of the A_max–N_area curve was greatest in the closest spacing, indicating a greater change in A_max per unit change in N_area. The two hybrid poplar clones had a similar morphophysiological response to changes of spacing. Both clones showed physiological acclimation of their foliage in response to intraclonal competition through modulation of SLA and PNUE.