Philips Park Tree Trail

Woodlands consist of several different ‘layers’ and microhabitats. The most apparent woodland layer is the canopy, made up of taller tree species, for example: oak, ash and lime. The mature trees of the canopy receive the majority of the sunlight hitting the woodland, and their leaves cast shade on everything growing beneath them. When a mature tree dies or falls, a gap opens in the canopy, helping the trees below gain access to much more sunlight. This creates a battle for succession in these bright clearings as other trees mature and attempt to claim a space in the canopy.

The canopy layer provides a home for tree dwellers such as buzzards and bats. The leaves of the trees are also a food source for a number of invertebrates, like the caterpillars of the winter moth. 

Next is the understorey, or shrub layer, containing smaller, younger trees and shrubs like hazel, holly and willow. Trees in the understorey are likely to branch out and grow in a wide, spreading fashion to catch as much light filtering through the canopy as possible. The understorey provides nesting and feeding opportunities for many birds and mammals. Invasive non-native species such as rhododendron are also found in the understory layer. They compete with native trees and shrubs and allow very little light to reach the next layer of the woodland. 

The herb, or field layer, sits below the understorey and consists of ferns, grasses, sedges and herbaceous plants. The field layer of a woodland varies a great deal, depending on the type of woodland. You might have twigged that the field layer will be much more densely covered in plants, where the canopy and understorey allow more light to reach the forest floor. Grazing and invasive species also have an effect on the development of the field layer. Himalayan balsam is an invasive non-native species in the UK. Thanks to its explosive seed dispersal mechanism, it spreads rapidly and quickly dominates the woodland field layer, preventing native plants from accessing light and growing. 

The final layer is the ground layer: the forest floor. This layer is made up of leaf litter, fungi, mosses, lichens and ivy. The ground layer is also home to a wide range of invertebrates and microbes living in the rich woodland soil.