A high-altitude temperate rainforest
Wistman's Wood is one of three high-altitude oakwoods remaining on Dartmoor. It grows at an elevation of 380–410 meters (1,250–1,350 feet) on the slopes of the West Dart River valley. The wood is a remnant of the forest that covered Dartmoor around 9,000 years ago, before being cleared by Mesolithic people starting about 7000 BCE. The dominant tree species is the Pedunculate Oak (Quercus robur). These oaks are noted for their dwarf stature; in 1620, they were described as "no taller than a man may touch to top with his head." Though they have grown since then, their average height is just 7 meters, with a maximum of around 12 meters.
The trees have contorted, gnarled forms, with branches often spreading horizontally across the ground. This growth pattern allows soil and organic matter to accumulate on the limbs, creating a habitat for other plants. Tree-ring studies of the oldest oaks show ages between 400 and 500 years. Despite their age, their growth is extremely slow. An oak felled in 1866 for study was found to be about 168 years old, with a trunk diameter of only 9 inches.
The science of stunted growth
The oaks' small size and twisted shape result from a combination of environmental pressures. The high altitude exposes the trees to strong winds that physically limit their vertical growth. The ground itself is a defining factor. The wood sits on a "clitter," a Dartmoor term for a field of large, angular granite boulders formed by frost weathering during past ice ages.
This rocky terrain creates two conditions that stunt the oaks. First, the soil between the boulders is thin, acidic, and poor nutrient availability. Second, the massive granite blocks physically obstruct root growth, preventing the trees from establishing a deep, supportive root system. This clitter floor has also protected the wood. The impassable boulders prevent grazing by Dartmoor ponies and cattle, which would otherwise destroy young saplings and prevent the forest from regenerating. The entire wood covers just 3.5 hectares (8.6 acres).
The trees and rocks are covered with a thick carpet of epiphytic mosses and lichens, which thrive in the damp air. Wistman's Wood supports over 100 species of lichen. The branches are characteristically covered in these growths, along with ferns like the common polypody. The wood is a designated Site of Special Scientific Interest (SSSI) primarily for this fragile ecosystem.