PEATLAND AND UPLAND BLACK SPRUCE POPULATIONS IN ALBERTA - MORPHOLOGY AND ECOPHYSIOLOGY

Morphology and ecophysiology of black spruce (Picea mariana (Mill.) B.S.P.) seedlings grown in a variety of controlled environments were studied in three pairs of adjacent peatland and upland black spruce populations from Alberta. Seedlings were grown in two greenhouse experiments as follows: (i) full factorial combinations of light (100 or 20% of full light in the greenhouse) and moisture (wet, medium, or dry); (ii) full factorial combinations of fertilization (fertilized or unfertilized) and substrate temperature (20 or 8-degrees-C at 5 cm below the surface). In both experiments, morphological (height, top dry weight, root dry weight, total dry weight, and top/root dry weight ratio) and physiological (net assimilation (NA), stomatal and mesophyll conductance to CO2 (g(c) and g(m)), and water use efficiency (WUE)) traits were measured. It was found that low light, nutrient stress, and water stress (wet or dry) reduced seedling growth. As moisture decreased or at low light, NA, g(c), g(m), and WUE decreased. When fertilized, seedlings at low substrate temperature were smaller and had lower NA, g(c), and g(m) than those at high substrate temperature. Results showed no differences in response to the experimental environments between seedlings from peatland versus upland populations. However, upland seedlings were larger than peatland ones, there was greater variation among peatland than among upland populations, and there were site-specific habitat differences. Overall, there was apparently little adaptive ecotypic differentiation in black spruce between the two habitats.