Forest community composition and dynamics of the Ossipee Pine Barrens, New Hampshire

In New Hampshire, the Ossipee Pine Barrens is the largest and best example of a Pinus rígida-Quer cus ilicifolia dominated ecosystem remaining in the state. Because of long-term fire suppression in the 20th century, we hypothesized that undisturbed stands may be undergoing succession to more shade-tolerant Pinus strobus and hardwoods. To test this hypothesis, we sampled 41 sites within the barrens covering the range of soils, landforms, stand age, and vegetational variation present in the barrens. Current (2002) tree (≥ 10 cm dbh) and sapling (taller than 1 m, < 10 cm dbh) densities were measured by quadrat sampling. Past (1952) vegetation was reconstructed using reverse-growth equations derived from increment cores from trees alive in 2002 and forensic evidence such as stumps. Future (2052) vegetation was estimated using a simple transition model based on 1952-2002 compositional changes. Community types were classified using cluster analysis of 80 communities based on the 2002 and back-casted 1952 tree species abundances at the study sites. Cluster analysis of the 80 communities using tree relative densities produced four community types, dominated by 1) P. rigida, 2) P. rígida and Acer rubrum, 3) P. strobus and A. rubrum, and 4) A. rubrum, respectively. The frequency of the Pinus rígida community type was highest in 1952 and declined with time, with only 8% of sites predicted to support pitch pine canopies by 2052. The Pinus strobus-Acer rubrum community type increased between 1952 and 2002 as the Pinus rígida type declined, and should continue to increase in the future. The other two communities appeared to be transitional. Pinus rígida was even-aged on most sites, where forests averaged 97 ± 42 years (SD) old. Many sites will transition to P. strobus and hardwoods as canopy pitch pines die, because P. rigida recruitment was not occurring in most stands.