Canopy Tree Project
Secrets of the Forest Floor
October 14, 2025
Forests are complex ecosystems composed of various layers defined by their distinct vertical zones, each with unique characteristics, sunlight levels, and inhabitants that contribute to the forest’s overall biodiversity and productivity. They all play a unique role in supporting biodiversity and productivity. In the forest context, productivity refers to the rate at which trees and plants use photosynthesis to convert sunlight, water, and nutrients into organic matter that can support the entire food web.
While it is easy to imagine towering trees with vast canopies of leaves as the most important part of a forest biome, one of the most influential layers of the forest can be found shrouded in the shadows underneath the green blanket of leaves.
Settled beneath the treetops and atop the forest floor is the forest understory, a middle layer of the forest made up of saplings, short trees, moss, and other vegetation that grows in the shade of the canopy. While these sapling trees that create the forest understory may be small, their role supporting the forest ecosystem is immense. The understory creates a critical habitat for a diverse range of wildlife, contributes to important nutrient cycling and soil health, and serves as a nursery for future canopy trees, playing a key role in forest regeneration and overall ecosystem resilience.
Hidden Habitat
From the largest mammals to the smallest insects, a wide variety of carnivores, omnivores and herbivores utilize the shady vegetation of the understory to hunt for prey and hide from predators.
In rainforests, this layer is home to many mammals and reptiles that have adapted to life in the low-light, humid environment. For example, tree snakes will often blend in with vines growing on trees to prevent being eaten. The dense vegetation, close to the ground, provides the perfect humid habitat for salamanders and frogs to reside and lay their eggs. Even flying animals such as bats and birds make use of the low-growing plants of the understory to fly over long distances.
In temperate forests, the understory also is home to a different selection of animal species. Possums, bandicoots, rabbits, and deer are herbivores that graze upon tender plants and saplings. Many birds and a vast array of insects also call this understory layer home, relying on the plants that grow here for nesting, foraging for food, and sheltering from predators.
Extreme Weather Resilience
As climate change contributes to rising global temperatures and increased extreme weather events, such as wildfires, our forests are facing heightened threats.
National Parks such as Yellowstone and Grand Teton have experienced multiple severe wildfires in recent years. In 1988, large fires burned nearly a third of the forest in Yellowstone and the outskirts of neighboring Grand Teton National Park and national forests. However, these wildfires did not cause permanent damage partially thanks to the diversity and resilience of perennial plants in the undergrowth.
Perennial plants are flowering plants such as blueberries, witch hazel, and mountain laure that come back to flower year after year. They often survive natural disasters such as wildfires because while their stems and leaves are burned, their roots protected deep in the soil remain unharmed. This allows understory vegetation to grow back over time and help restore forest ecosystems, while larger trees take longer to regrow.
Saving Our Soil
Along with the role understories play in mitigating the damage of wildfires and restoring forests, the vegetation that thrive at this forest layer are also crucial in preventing soil erosion and absorbing the greenhouse gas, carbon dioxide.
Understory layer plants and vegetation protects soil from being disturbed by water as their leaves lighten the impact of raindrops. Heavy raindrops can hurt the soil by hitting the ground with enough force to break apart the soil, dislodging and loosening it, and making it easier for water runoff to carry it away, causing soil erosion.
Additionally, the roots of plants in the understory layer like creeping juniper, periwinkle, and big blue lilyturf, don’t just help hold the soil firmly in place. Their root systems improve the soil’s ability to soak up water. This helps to limit the amount of water runoff in forests during heavy rainstorms, further preventing the soil and nutrients from being washed away.
In areas where there is little to no understory vegetation, for example in tree crop plantations, there are increased rates of soil erosion.
Carbon Sinks
Understory vegetation contributes significantly to our forest’s role as a carbon sink by absorbing carbon dioxide through photosynthesis, even under the low light conditions typical of the forest floor. While large trees account for most of the carbon dioxide absorption in forests, the understory plays an important role in carbon sequestration that should not be underestimated. The leaves, stems, root systems, and litter of understory plants stores an estimated average of 3.9 metric tons of carbon per hectare.
Additionally, understory species adjust leaf nitrogen content to maximize carbon take up in these sorts of shaded environments. This helps to regulate forest carbon dynamics and overall ecosystem productivity.
Natural Nutrients
The smaller trees, shrubs, and plants that make up our forest’s understory have learned to thrive beneath the tall trees of the forest. They are primary producers, making their own food from sunlight and water, which in turn becomes food for many animals and insects. Also, understory vegetation on average introduces and recycles nutrients at a faster rate through the food chain because they grow and renew much faster than woody plants.
This means they provide an important and accessible food source for many herbivores like deer and rabbits. For example, in northern hardwood forests, wildflowers such as trilliums and bloodroot push through the leaf litter in early spring before the bigger trees fully leaf out, giving pollinators and small animals a vital source of energy at that time.
Small trees and shrubs absorb minerals and other nutrients such as potassium, calcium and nitrogen from the soil. Nitrogen is especially important because it is a key building block for chlorophyll—the green pigment that plants use to capture sunlight and make their own food through photosynthesis. Plants absorb nitrogen through their roots mostly in simple forms called inorganic nitrogen, mainly nitrate and ammonium, which are made available in the soil when microbes break down dead plants and animals. Without enough nitrogen, plants cannot grow properly or stay healthy.
Afterwards, all of these nutrients are stored in the plant, in their flowers, roots and leaves, and are then transferred to animals as they eat this vegetation. These nutrients then move up the food chain as herbivores like rabbits (primary consumers) are eaten by predators such as big cats, foxes, and wolves (secondary and tertiary consumers).
When all plants and animals eventually die, these nutrients are released back into the soil and broken down by decomposers such as earthworms and fungus. Then, the understory vegetation absorbs these nutrients back through their roots and recycles them back into the food chain.
Heart of the Forest
While easily disregarded, forest understories are crucial to the health and productivity of all forest ecosystems.
With climate change fueling changes in these ecosystems every day, protecting our forests has never been more important. Help us support the preservation of the world’s forests by donating to the Canopy Tree Project – so we can continue to work with communities around the world and plant more trees!
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