The Undergrowth in the Forest of Saint-Germain: Shrubs, Trees, and Their Role
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Understory in a forest plays a many-sided role in the life of a forest stand. The understory is made up of shrub and tree species that grow in the lowest layer and never reach the upper canopy: hazel, buckthorn, honeysuckle, elderberry, daphne (wolf's bane), and goat willow.
How does the understory affect the forest environment?
The understory exerts a very large influence on the forest environment, shaping soil, moisture, and the conditions in which the upper layers grow. Its effects are mostly beneficial, but the same trait can act differently on different species.
- The fallen leaves of understory plants decompose faster than the leaves of the upper layers, which means they also form soft humus more quickly.
- The understory has to make do with less light, so it is shade-tolerant.
- Shrubs shade the soil and prevent moisture from evaporating, and they hinder the growth of grass, which benefits the trees.
- Another positive quality of the understory: some of its species carry nodules on their roots containing microorganisms that fix nitrogen from the air.
When does the understory harm the tree stand?
The understory sometimes has a negative effect on the tree stand, because the very same qualities act differently on different species. For example, the understory blocks solar radiation and warmth from reaching the soil, and this is disadvantageous for heat-loving species (more on this: Trees that love warmth).
A spruce understory, for instance, interferes with the regeneration of pine. Sometimes it is more profitable to remove the understory, and sometimes, on the contrary, to introduce it — the right choice depends on which species the forester wants to favour.
