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Welcome to Holt Research Forest

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Long-term ecosystem research in a mid-coast Maine oak-pine forest since 1983.


The Holt Research Forest is a 120-hectare (300 acre) forest located in Arrowsic, Maine. Arrowsic is similar to the peninsulas of the mid-coast region, but is actually an island surrounded by the Kennebec River to the west and south, the Sasanoa River to the north and east, and the Back River to the east. The island falls within Maine’s coastal climatic region and the midcoast biophysical region of Maine. This region has the greatest woody plant species richness in the state in part because it falls within the transition between the oak-pine forest to the west and south and the spruce-fir forest to the east and north. The soils are derived from shallow glacial deposits on ridges and deep glaciomarine sediments in low-lying areas.

The forest is predominantly a dry ridge, oak-pine ecosystem typical of mid-coastal Maine. Parts of the property were farmed from the late 1600s to the 1940s, but most of the cleared land was abandoned by the  early 1900s, resulting in a canopy that in 1983 was dominated by 60- to 80-year-old trees. Today the most abundant tree species by volume and number are Eastern White Pine (Pinus strobus), Northern Red Oak (Quercus rubra), and Red Maple (Acer rubrum). The oldest trees were 125-year-old, heavy-limbed, eastern white pines and eastern hemlocks that grew along fence rows and drainage ways, a few still remain today. The understory includes shrubs such as Vaccinium, Gaylussacia, Viburnum, and Juniperus. Common herbs include Mainthemum, Cornus, Gaultheria, Mitchella and Trientalis.