Water relations parameters of lowland and upland black spruce: seasonal variations and ecotypic differences

Abstract

Weekly values of water relations parameters of four black spruce (Piceamariana (Mill.) B.S.P) populations growing in a common garden north of Québec City were obtained by pressure–volume curve analysis from mid-May to mid-October 1991. Two of the four populations originated from the province of Quebec, and two were from Ontario. Within each geographical location, one population was from a lowland site (peat soil) and the other from an upland site (well-drained sandy soil). Differences between upland and lowland populations were small but statistically significant for the majority of water relations parameters in the Ontario pair. No significant differences could be found between populations in the Quebec pair. In the Ontario pair, trees from the lowland site exhibited some traits that could be associated with water-stress tolerance, such as lower relative water content at turgor loss point, lower maximum modulus of elasticity, lower osmotic potential at turgor loss point, and higher osmotic amplitude for turgor maintenance. The seasonal pattern of water relations parameters was similar among the four populations and also similar to patterns that have been reported for other species. The seasonal variations in water relations parameters followed phenological changes that were driven by seasonal shifts in environmental parameters.