Factors affecting plant community composition and dynamics in the Ossipee Pine Barrens, New Hampshire

Abstract

Forty-one 0.25 ha sites were sampled in the Ossipee Pine Barrens to identify and describe tree community types and investigate factors controlling forest composition and dynamics. Every site had three site-time assemblages (STA\u27s) representing past, present, and future trees. Past (1952) vegetation was calculated based on reverse growth estimates of current stems and stumps. Future (2052) vegetation was predicted by current sapling (\u3c10 cm dbh and ≥1 m tall) relative densities. Cluster analysis produced three community types from 121 STA\u27s: pitch pine, mixed pine-hardwoods, and red maple. Pitch pine communities comprised 63% of sites in 1952, but declined since. Mixed pine-hardwoods peaked at 58% in 2002, but were predicted to decline to 37% by 2052 as sites transitioned to red maple. The red maple community only appeared in the future after current saplings replaced aging pitch pine canopies, but the type was predicted to comprise 50% of sites by 2052. Assuming continued fire suppression, pitch pine communities will retain only 12% of sites by 2052. Control over vegetation patterns and successional dynamics by (1) soils, (2) seed source, and (3) disturbance was investigated using field evidence, accounts from residents and forest managers, and dendrochronology. Factors affecting forests since stand formation were analyzed individually and with multivariate techniques. Seed source variables explained the greatest amount of variation in vegetation, followed closely by fire-related disturbance variables and weakly by soil texture. Logging disturbance and soil nutrients were not significant predictors of vegetation in the Ossipee Pine Barrens