Selected Nova Scotia old-growth forests: Age, ecology, structure, scoring

Abstract

A study of four old-growth stands in Nova Scotia was conducted to document the ecological characteristics of these currently rare Acadian forest ecosystems. Stands were selected to represent the two dominant climax forest types, hemlock–red spruce–eastern white pine, and sugar maple–yellow birch–beech. Data include measurements of age structure, species composition, diameter distribution, basal area, height, coarse woody debris, snags, vertical structure, and canopy condition. All stands were determined to be uneven-aged. Old-growth reference ages calculated for the stands ranged from 164 to 214 years. All stands displayed broad diameter distributions that had peak basal area representation in the 40- to 50-cm diameter classes. Volumes of dead wood ranged from 111 to 148 m3/ha in the softwood stands and from 63 to 83m3/ha in the hardwood stands. Dead wood consisted of approximately one-third snags and two thirds downed coarse woody debris. Measurements from the stands were used to evaluate Nova Scotia's recently developed Old Forest Scoring System. Six stand attributes were rated for a maximum score of 100: stand age, primal value, number of large-diameter trees, length of large-diameter dead wood, canopy structure, and understorey structure. Based on the age attribute, three of the four stands were classed as Mature Old Growth and one was very close, indicating that all are in the shifting mosaic stage of late forest succession. The scores for all stands were relatively high, ranging from 75 to 85, as would be expected from some of the best old-growth stands in the province. Key words: old growth, climax, primal, late succession, uneven-aged, scoring, coarse woody debris, age structure, diameter, Acadian forest, northern hardwood, red spruce, eastern hemlock, white pine, sugar maple, yellow birch, American beech