Habitat-dependent morphological and chemical variation in Picea mariana from northwestern Ontario

Abstract

To determine whether local site differences corresponded to any morphological or chemical differentiation in Picea mariana, 10 cone-bearing trees were sampled from each of three semiadjacent stands near the Matawin River, Thunder Bay District, Ont.: (i) an upland forest on well-drained alluvial soil, (ii) an abandoned pasture on heavy soil, and (iii) a wet sphagnum bog. Nine cone characters and eight needle and twig characters were scored and analyzed. Differences among sites were generally small. Principal-components analysis demonstrated two major, independent trends of variation, one attributable mainly to cone characters and the other to needle characters. Bog trees tended to be more variable than the others with respect to cone characters but had similar levels of variation for needle and twig characters. Further comparisons were made based on foliar flavonoids of the 30 trees and isozyme characteristics of an expanded sampling of 60 trees. Flavonoid analysis indicated that a fraction of the bog trees possessed flavonoid diglycosides not present in the other trees. Five polymorphic enzyme systems were detected in electrophoretic analysis. Trees from the three sites had similar isozyme patterns with the exception of three bands that were unique to the bog site trees. Thus, the bog trees were more variable for cone, flavonoid, and isozyme characters but exhibited no greater variability for needle and twig characters. However, none of the data gave an indication of discrete ecotypes of black spruce corresponding to upland and lowland sites.