The Understory
Photo of Carolina Wren by Ryk Naves
The understory sits between the forest floor and the canopy. This middle layer is a lively, important part of the ecosystem, supporting a wide variety of plants, animals, and fungi. It’s the area humans are most familiar with, too.
Life in the Understory
The understory is home to a diverse array of life in all types of forests. Small mammals like squirrels and mice find shelter among the dense vegetation, while monkeys swing through the lower branches in search of food. Frogs, toads, and salamanders (amphibians) take advantage of the moisture collecting in this sheltered layer. Birds like owls, parrots, and thrushes find food and build nests here, using the dense cover to protect their young from predators. And of course, all sorts of insects crawl and fly through this part of the forest, pollinating and helping with decomposition.
The understory is where the widest variety of plants grow in the forest. Shrubs like azaleas and holly, along with younger trees reaching for the sun, fill this layer. Ferns and palms enjoy life in the shade, their broad leaves capturing the limited sunlight that filters through the taller trees above. Orchids and bromeliads cling to tree trunks, drawing moisture and nutrients from the air rather than the soil.
Fungi, too, live in the understory. Turkey tail and sulphur shelf grow directly on tree trunks, while Artist conk forms large, woody brackets on the sides of trees. These fungi not only help decompose organic matter but also contribute to the complex interactions between plants, animals, and microorganisms in the forest.
Photo of Artist Conk (Ganoderma applanatum) by Anya Chernik
The Understory’s Importance
The whole forest relies on the understory, but what makes it so important?
Light Filtering and Temperature Regulation: The canopy’s leaf cover creates a cooler, shaded environment below that helps moderate the temperature in the forest.
Buffer Zone: The understory is a buffer between the forest floor and the canopy, helping protect the lower layers from strong winds or heavy rains by absorbing the impact before it reaches the ground.
Seedling Growth and Tree Regeneration: This region is the forest’s nursery for its younger trees. The moderate light levels and sheltered conditions are ideal for seedlings, where they can grow slowly and steadily until they’re strong enough to compete for sun up in the canopy.
Species Interactions: The understory is a zone of intense interaction between species. Predators and prey, pollinators and plants, decomposers and organic matter—all engage in a complex web of relationships that help the forest's biodiversity. Fungi influence the health and growth of plants, while animals disperse seeds, for example.
The Bottom Line
The understory is a dynamic layer that supports a wide range of life and the overall health of the forest’s ecosystem. By filtering light, providing diverse habitats, acting as a buffer, supporting seedling growth, and fostering species interactions, the understory helps a forest grow and stay strong and resilient. Next time you’re in a forest, take a look around at the wild diversity and how it all fits together.
