© 2001 Heron Publishing—Victoria, Canada
Photosynthesis and carbon allocation of six boreal tree species grown in understory and open conditions
Simon M. Landhäusser (1) and Victor J. Lieffers (1)
1. Department of Renewable Resources, University of Alberta, Edmonton, Alberta T6G 2E3, Canada / Received February 11, 2000
Summary
One-year-old seedlings of Abies balsamea (L.) Mill, Picea glauca (Moench) Voss, Pinus contorta Loudon, Betula papyrifera Marsh., Populus tremuloides Michx. and Populus balsamifera L. were transplanted in the spring, in pots, to the understory of a mixed P. tremuloides–P. balsamifera stand or to an adjacent open site. Growth and leaf characteristics were measured and photosynthetic light response curves
determined in mid-August. Overall, the coniferous seedlings showed less photosynthetic plasticity in response to growth conditions
than the deciduous species. Abies balsamea, P. glauca and B. papyrifera responded to the understory environment with higher leaf area ratios, and lower photosynthetic light saturation points and
area-based leaf respiration relative to values for open-grown seedlings, while they matched or exceeded the height growth
of open-grown seedlings. In contrast, seedlings of Pinus contorta, P. tremuloides and P. balsamifera displayed characteristics that were not conducive to survival in the understory. These characteristics included a high light
saturation point and leaf dark respiration rate in P. contorta, and lower leaf area variables combined with higher carbon allocation to roots in P. tremuloides and P. balsamifera. By the second growing season, all seedlings of P. tremuloides and P. balsamifera growing in the understory had died.
Keywords:
Abies balsamea, Betula papyrifera, boreal forest, light response curves, Picea glauca, Pinus contorta, Populus balsamifera, Populus tremuloides, shade tolerance.
