While the focus of much of the Foundation’s research and management has been on globally rare sandplain grasslands and heathlands, Nantucket’s forests are an unusual and important part of the island ecosystem. Squam Swamp and Squam Farm host some of the largest forest tracts on Nantucket, containing many large, old trees. Large red maple trees dominate Squam’s low-lying wetlands, while the upland forests contain stands of slender tupelo and sassafras, with scattered large black and white oak trees and copses of American Beech. Unlike mature trees in mainland forests, Squam’s largest trees typically have canopies that branch very low to the ground and often consist of several sizable trunks.
These are uncommon plant communities on Nantucket that appear to contain different species composition and lower diversity than comparable mainland forests. Nantucket’s “forests at sea” have been strongly impacted by the island’s history of sheep grazing and deforestation. Forest structure and composition are also likely shaped by the maritime climate of the island, which includes high winds and salt spray, combined with ocean moderated temperatures and high humidity.
We documented the composition and structure of Squam’s forests in order to refine management of these conservation properties, with the goal of protecting their diversity and unique character. Collected data includes species, age and stand structure for the canopy tree layer. Additionally, information on the shrub understory, tree seedlings, groundcover plants and presence of invasive species is being used to assess deer impacts and future tree establishment. Increasing deer populations have been documented in forest communities elsewhere in the Northeast, but to date there has been no research on the effects of deer on Nantucket’s forests. Concentration of deer herds in these areas may shape future forest composition, as deer have been found to reduce native plant diversity while facilitating the spread of invasive plant species. This research is in the process of being prepared for publication.