Vegetation and disturbance history of a rare dwarf pitch pine community in western New England, USA

Aim This study documents the vegetation history and age-structure of a rare, ridgetop dwarf pine–oak community and compares the dynamics of this unusual vegetation with similar dwarf pine communities found elsewhere in the north-eastern United States (US). Location The study area is located on the summit of Mt Everett in the Taconic Mountains of south-western Berkshire County, Massachusetts, USA (42 06¢N 73 26¢W). Methods Vegetation composition, tree age-structure, physical site characteristics, and evidence of fire and other disturbances were determined for twelve 15 · 15 m plots in dwarf pine–oak vegetation and two plots in oak forests on the summit. Age-structure analyses, tree-ring patterns, and historical records of human and natural disturbance were used to investigate the long-term history and dynamics of the summit vegetation. Results The summit of Mt Everett has been dominated by dwarf pines (1–3 m tall) and ericaceous shrubs similar to the modern vegetation throughout the historical period; there is no evidence that tall-stature forests occurred on the site at any point in the past few centuries. The summit supports uneven-aged stands; pitch pine (Pinus rigida) recruitment began in the 1830s and occurred in every decade since the 1860s. Average pitch pine age is seventy-eight with a range of 12–170 years. Red oak (Quercus rubra) and red maple (Acer rubrum) increased in importance in the twentieth century, with most stems establishing from 1940 to 1980. Pitch pine radial growth rates averaged <0.5 mm year while red oak and red maple averaged 1.0 and 0.8 mm year, respectively. In some areas, hardwoods have overtopped pitch pines, apparently resulting in pitch pine mortality. Whereas most dwarf pitch pine communities occur on sites that burn frequently and have a high degree of cone serotiny, we found no evidence of recent fires or cone serotiny. Small amounts of macroscopic charcoal that we documented may have resulted from fires in the pre-European or early historical periods. Conclusions Harsh edaphic conditions and chronic low-level disturbances on the summit, including frequent winter storms, have apparently contributed to the establishment, long-term persistence, and slow radial growth of dwarf pitch pines on Mt Everett. The ability of dwarf pines to persist on a site in the absence of frequent fire is highly unusual among North-eastern barrens and has not been well-incorporated into previous conceptual ecological models of these communities. Our results suggest that even among North-eastern barrens, the summit of Mt Everett is characterized by highly unusual vegetation and dynamics. The site has long been recognized as regionally significant and should be afforded the strictest conservation protection. With no evident history of human disturbance or recent fire, there is no apparent need for immediate active management of the site.