© 2000 Heron Publishing—Victoria, Canada
Physiological responses of black spruce layers and planted seedlings to nutrient addition
Raynald Paquin (1), Hank A. Margolis (2), René Doucet (1) and Marie R. Coyea (2)
1. Direction de la recherche forestière, ministère des Ressources naturelles du Québec, 2700 rue Einstein, Sainte-Foy, Québec
G1P 3W8, Canada / 2. Centre de recherche en biologie forestière, Faculté de foresterie et de géomatique, Université Laval, Sainte-Foy, Québec G1K
7P4, Canada / Received June 8, 1998
Summary
We investigated effects of nutrient addition on several physiological characteristics of 60-cm-tall black spruce (Picea mariana Mill. B.S.P.) layers (i.e., rooted branches of overstory trees) and 20-cm-tall planted seedlings on a clear-cut, N-limited
boreal site. After two growing seasons, current-year and one-year-old needles of fertilized trees (layers and seedlings combined)
had higher net photosynthetic rates (An) and maximum capacity of Rubisco for CO2 fixation (Vmax) than unfertilized trees. One-year-old needles of fertilized trees had higher stomatal conductance (gs), higher water-use efficiency, and lower intercellular to ambient CO2 ratio than unfertilized trees. Additionally, fertilized trees had higher predawn and midday shoot water potentials than unfertilized
trees.
Stomatal conductance of 1-year-old needles was 23% higher in seedlings than in layers, but there were no significant differences
in gs of current-year needles between the regeneration types. For both needle age-classes, An and Vmax of layers were 25 and 40% higher, respectively, than the corresponding values for seedlings. The higher values of An, Vmax and foliar N concentration of layers compared with seedlings after two growing seasons may be associated with the larger
root systems of the layers compared with the transplanted seedlings.
Keywords:
fertilization, photosynthesis, Picea mariana, Rubisco capacity, stomatal conductance, water stress, water-use efficiency.
