The Mt. Holyoke Range constitutes one of the largest remaining unfragmented forests in Massachusetts (over 8,000 acres, including Mount Tom). A rich mixture of oak, pine and hemlock, the forest protects the water quality of streams that feed the Connecticut River nearby. It is also a landmark used by thousands of migrating birds in the fall, including several federally-listed species.
Geology has strongly influenced the plant communities found here. South-facing slopes, with more nutrient-rich, circum-neutral soils, support an Oak-Hickory forest more common further south. By contrast, on north-facing slopes, with more acidic soils, the forest is largely composed of Hemlock, White Pine, Birch, Beech, and Maple, an association more typical of New England’s cold, moist habitat. Certain rocky outcrops (called “the Balds”) also support an unusual plant community featuring species typical of the tall-grass prairie far to the west. The mountain shelters a thriving wildlife population, including deer, foxes, songbirds, and raptors.
At Skinner State Park we see large-diameter hemlock trees along the Tramway Trail’s and Halfway House Trail’s upper reaches. The hemlocks are so large because they are “old growth,” some well over 200 years in age. Trees with multiple trunks are conspicuous by their absence. This is so because trees here were neither killed by forest fire nor felled by axe. These woods are telling the story of land kept as a “natural” tourist destination for over 150 years.
Rocks tell the story of what was going on when they were formed and sometimes the story of subsequent events. The basalt rock that shapes the Range’s spine and south-facing slopes is a dense igneous rock. Its extremely fine-grained texture tells us that it cooled rapidly at Earth’s surface, when this area was part of an enormous rift valley some 200 million years ago. Its reddish cast indicates the presence of iron. Some of the basalt on the Range has shallow, smooth grooves, about as wide as a thumb, running in long parallel lines. This is the signature of a glacier, grinding along the rock on its journey south during the last ice age.