Foliage‐Height Profiles and Succession in Northern Hardwood Forests

Abstract

Leaf area index (LAI) and foliage—height profiles were determined for 13 northern hardwood stands ranging from 3 to 57 yr since clearcutting and for 1 uncut stand. Leaf litter collection and stratified clipping were used to measure LAI which showed no relationship to total canopy height or foliage—height distribution, and recovered quickly to near mature forest levels following cutting. A camera and telephoto lens were used to measure the distribution of heights to lowest leaf in the 12 oldest stands (7 / yr). Distributions were converted to foliage—height profiles using equations from MacArthur and Horn (1969). Profiles in the 2 youngest stands (3 and 4 yr) were determined by stratified clipping. Total canopy height varies predictably with age and is the major determinant of foliage—height diversity calculated using data in 1—m intervals by height. The concentration of foliage into a definable stratum occurs early in succession and persists through year 30. An associated lack of understory in this period results in a reduced foliage—height diversity using data normalized to a 4 strata per profile. Beyond year 30, canopy structure is variable but mature stands generally have leaves evenly distributed by height.