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, the Sasanoa River to the north, and the Back River to the east and south. The island falls within Maine’s coastal climatic region (Briggs and Lemin 1992) and the midcoast biophysical region of Maine (McMahon 1990). 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 1600's to the 1940's, but most of the cleared land was abandoned by the early 1900s, resulting in a canopy dominated by 60 to 80 year-old trees. The oldest trees are 125-year-old, heavy-limbed, eastern white pines and eastern hemlocks that grew along fence rows and drainage ways. The understory includes shrubs such as Vaccinium, Gaylussacia, Viburnum, and Juniperus. Common herbs include Mainthemum, Cornus, Gaultheria, Mitchella and Trientalis.
A grid system has been superimposed over the Holt Research Forest. Each square is a 1-hectare "block", further subdivided into 0.25 ha "quadrats" and 0.0625 ha "subquadrats". The main study area consists of a central 40-ha area between Sewall Pond and the Back River.