© 2001 Heron Publishing—Victoria, Canada
Growth and dry-matter partitioning of young Populus trichocarpa in response to carbon dioxide concentration and mineral nutrient availability
Bjarni D. Sigurdsson (1, 2), Halldor Thorgeirsson (3) and Sune Linder (1)
1. Department for Production Ecology, Swedish University of Agricultural Sciences, P.O. Box 7042, SE-750 07 Uppsala, Sweden / 2. Icelandic Forest Research, Mogilsa, IS-116 Reykjavik, Iceland / 3. Agricultural Research Institute, Keldnaholt, IS-112 Reykjavik, Iceland / Received March 15, 2000
Summary
Young individuals of a single black cottonwood (Populus trichocarpa Torr. & Gray) clone were raised for three growing seasons in whole-tree chambers and exposed to either ambient or elevated
atmospheric carbon dioxide concentration ([CO2]), with either a high or a low mineral nutrient supply, in a factorial experimental design. Nutrient availability had a larger
effect on growth and dry matter partitioning than did [CO2]. Total biomass did not differ significantly with CO2 treatment when nutrient availability was low. However, elevated [CO2] increased whole-plant biomass by 47% in the high nutrient availability treatment. Carbon dioxide enrichment reduced leaf
area ratio and specific leaf area significantly, but had no significant effect on mean leaf size or leaf mass ratio. Root
mass ratio was significantly increased by elevated [CO2] at low, but not at high nutrient availability. A modified “demographic harvesting approach” made possible the retrospective
estimation of stem and branch dry masses for different years. The relative growth rates of stem and branch were significantly
enhanced by elevated [CO2] with high, but not with low nutrient availability. Canopy productivity index (CPI), i.e., the amount of stem and branchwood
produced annually per unit leaf area, was raised 12% by elevated [CO2] when nutrient availability was high, but was reduced when nutrient availability was low, because of increased belowground
allocation.
Keywords:
allocation, growth analysis, leaf area, nitrogen status, poplar, root:shoot ratio.
