© 1986 Heron Publishing—Victoria, Canada
Effects of carbon dioxide enrichment and nitrogen supply on growth of boreal tree seedlings
Kevin Brown and K. O. Higginbotham
Department of Forest Science, University of Alberta, Edmonton, Alberta, Canada, T6G 2H1 /
Summary
The effects of two levels of atmospheric carbon dioxide (350 μl l–1, 750 μl l–1) and three levels of nitrogen (15.5 mM, 1.55 mM, 0.155 mM N) on biomass accumulation and partitioning were examined in aspen
(Populus tremuloides Michx.) and white spruce (Picea glauca (Moench) Voss) seedlings grown in controlled environment rooms for 100 days after germination.
Nitrogen supply had pronounced effects on biomass accumulation, height, and leaf area of both species. Root weight ratio (RWR)
of white spruce was significantly increased at the lowest level of nitrogen, whereas RWR of aspen did not change much with
increasing levels of nitrogen.
Carbon dioxide enrichment significantly increased (1) the leaf and total biomass of spruce seedlings grown in the high-N regime,
(2) the RWR of seedlings in the medium-N regime, and (3) the root biomass of seedlings in the low-N regime after 100 days.
Carbon dioxide enrichment of aspen temporarily increased biomass and height in all three nitrogen regimes. Root, stem, and
leaf mass, height, and leaf area of aspen were increased only at the 30-day harvest in the high-N treatment and at 50 and
60 days in the low-N treatment. Height, stem biomass, and leaf biomass of aspen seedlings were significantly increased by
CO2 enrichment after 40 days in the medium-N treatment. These effects did not persist, possibly because of the onset of mineral
nutrient supply limitations with increasing plant size.
