The Hidden Helpers of Our Forests: Mycorrhizal Fungi and the Web of Life Beneath Our Feet

By Laura Gilmore

When we walk through a forest in Northern Virginia, whether it’s the hardwoods of Potomac Overlook Regional Park or the woodlands of Glencarlyn Park in Arlington, it’s easy to focus on what we can see: towering oaks, spring wildflowers, and calling birds overhead. Yet some of the most important activity in our forests is happening quietly beneath the soil surface. Below the visible world lies a hidden network that is essential to the health and resilience of our forests.

This underground world is linked by mycorrhizal fungi, microscopic fungal partners that form close, symbiotic relationships with tree roots, and the roots of nearly all other plants. The word mycorrhiza literally means “fungus-root.” This association enables trees to access water and nutrients in ways their roots alone could never achieve. The fungi do this by extending fine, thread-like structures called “hyphae” far into the soil. In exchange for sugars produced by trees through photosynthesis, mycorrhizal fungi increase uptake of water and nutrients such as phosphorus and nitrogen, which are often scarce in forest soils. Trees colonized mycorrhizal fungi by can grow 10-20% faster than non-colonized trees, even though they are ”giving away” up to 40-50% of their liquid carbon to support and feed the mycorrhizal networks.

This mutualism between fungi and trees does not just benefit individual trees; rather, it links forests together. Mycorrhizal networks often connect multiple trees across species underground, forming a “wood-wide web,” so that trees can exchange resources. This networked system allows forests to function less like collections of individual trees and more like interconnected communities. Research even suggests that larger or healthier trees may transfer sugars to shaded seedlings, helping them survive until they reach sunlight, and the fungi help protect against pests and diseases. 

These fungal partnerships are at work in area forests, supporting familiar species such as oaks, tulips, beeches, and maples. The strength and resilience of our local forests depend heavily on healthy soil, and that soil depends on fungi. Disturbances that damage soil structure can also damage these fungal networks. Excessive clearing, removal of leaf litter and fallen logs, soil compaction, and construction can all disrupt mycorrhizal fungi. When these networks are broken, trees may become more vulnerable to drought, disease, and stress, with ripple effects throughout the ecosystem.

While fungi support the root health of forests, another group of hidden organisms reflects forest health above ground. Northern Virginia forests are home to several salamander species, including the Eastern red-backed salamander, which is commonly found beneath logs and leaf litter in moist woodland habitats. Salamanders rely on damp soil conditions and decaying organic matter to avoid desiccation, maintain cover, and prey on invertebrate populations.

Because salamanders are so sensitive to changes in soil moisture, temperature, and chemistry, they are often considered indicators of forest health. When salamander populations decline, it can be an early sign that something is wrong beneath the forest floor, often before problems are visible above ground. In this way, salamanders and fungi are closely linked and protecting one helps protect the other. Healthy fungal communities help create the cool, damp habitat salamanders depend on.

Fortunately, there are simple stewardship actions we can take to support these hidden networks:

• Minimize soil disturbance by staying on designated trails in parks and forests.
• Leave leaf litter and fallen logs in natural areas whenever possible; they provide food for fungi and habitat for wildlife.
• Support forest conservation and restoration projects (such as invasive species removal) that prioritize soil health.
• In home landscapes, consider reducing excessive soil disturbance and allowing some natural leaf litter to remain beneath trees.

Leaving natural materials in place supports the hidden community that sustains forest health. By learning to value what lies beneath our feet, from fungal threads to salamander pathways, we gain a deeper understanding and appreciation for the complexity and resilience of Virginia’s forests. The most important connections in nature are often the ones we never see, but they are always there, holding the forest together.