Population density and height distribution of Corylus cornuta in undisturbed forests of Minnesota: 1965–1984

Abstract

This study examined hazel populations (chiefly Corylus cornuta Marsh.) over a 19-year period on 232 permanent plots in 29 mature undisturbed stands in five forest types in northern Minnesota. The density, frequency, and height of hazel were greater in the jack pine – red pine, red pine, and aspen–birch types than in the maple–basswood and fir–spruce types. In the red pine and aspen–birch types, hazel density decreased about 30% from 1965 to 1975 and then increased between 30 and 18% from 1975 to 1984. These shifts in density were unrelated to changes in the density of the overstory or of other shrubs. In the maple–basswood type hazel density declined 61% from 1965 to 1984; shade tolerant overstory simultaneously increased. Height distribution generally followed a pattern in which density decreased with height and probably with age. This distribution indicates that hazel stands are maintained by continual recruitment of new stems.