Why Some Trees “Talk” Through Underground Fungal Networks
Walk through a healthy forest and most of what captures your attention is above ground: columns of bark, overlapping leaves, birdsong, shifting light and perhaps a mushroom pushing through the leaf litter. Yet a large part of the forest’s activity takes place out of sight, where roots, fungi, bacteria, water and minerals interact inside a living soil ecosystem.
Among the most important participants are mycorrhizal fungi. These fungi form close associations with plant roots and grow threadlike structures called hyphae through the soil. The partnership can help plants obtain nutrients and, in some circumstances, water. In exchange, the fungi receive carbon-rich compounds produced by plants through photosynthesis.
Some fungal individuals can colonize more than one plant, creating what scientists call a common mycorrhizal network. This biological reality inspired the catchy phrase “Wood Wide Web.” The comparison is memorable, but it must be handled carefully: trees do not speak, think or consciously send gifts. Underground transfers and signals can occur, but scientists are still investigating how common, important and beneficial they are in natural forests.
Fact-checked against scientific and government sources · August 2026What Is a Mycorrhiza?
The word mycorrhiza refers to an intimate association between a fungus and a plant root. Rather than simply growing beside the root, the fungus forms specialized contact points where resources can be exchanged. The relationship is ancient and widespread, occurring in most major terrestrial ecosystems and involving the majority of land-plant species.[1]
Plants manufacture carbon compounds using sunlight, carbon dioxide and water. Some of this carbon is transported below ground and supplied to fungal partners as sugars, lipids or related compounds. The fungus uses that energy to grow a network of microscopic hyphae into spaces in the soil that roots may not reach efficiently.
Through those hyphae, fungi can acquire mineral nutrients such as phosphorus and nitrogen. These elements are essential for plant growth but may be chemically bound, unevenly distributed or difficult for roots to access. Mycorrhizal hyphae effectively expand the zone from which a plant can obtain resources.[2]
Two Major Types of Mycorrhizal Partnership
Arbuscular mycorrhizae
Arbuscular mycorrhizal fungi enter the outer cells of roots and form tiny, highly branched exchange structures called arbuscules. They associate with many grasses, crops, tropical trees and other plants.
- Especially important in phosphorus acquisition
- Common in grasslands, farms and many tropical forests
- Belong mainly to the fungal subphylum Glomeromycotina
Ectomycorrhizae
Ectomycorrhizal fungi form a sheath around fine roots and grow between root cells rather than penetrating them. They are prominent partners of many pines, oaks, beeches, birches and eucalypts.
- Common in temperate and boreal forests
- Often involved in nitrogen and phosphorus acquisition
- Many familiar forest mushrooms are their fruiting bodies
These categories differ in anatomy, fungal ancestry, host plants and ecological effects. There is therefore no single underground network that behaves identically in every forest. A tropical woodland dominated by arbuscular mycorrhizal trees may function very differently from an ectomycorrhizal pine or beech forest.
How the Underground Exchange Works
This is not a fixed-price transaction. The amount and direction of exchange can change with nutrient availability, plant species, fungal identity, root anatomy, light, temperature, moisture and the physiological condition of both partners. Under some conditions the association strongly benefits the plant; under others, its costs may equal or exceed its immediate benefits.
Modern experiments show that fungi and plants can adjust their allocation of resources. A fungus may move more nutrients toward roots that provide more carbon, while plants may favor fungal partners that deliver useful nutrients. The system resembles a biological market more than a charitable distribution network.
What Is a Common Mycorrhizal Network?
A common mycorrhizal network forms when the hyphae of a fungus connect with the roots of two or more plants. Those plants may belong to the same species or to different species that are compatible with the same fungus.
Researchers have demonstrated such connections in laboratory systems, controlled field experiments and natural environments. Isotope tracers have also detected movement of carbon and mineral nutrients between plants associated with fungal pathways.[3] These findings establish that belowground transfer is biologically possible.
What they do not automatically establish is that the transfer is large, intentional or beneficial to the receiving plant. A detected isotope may represent a very small amount of material. It may move through fungal tissue, leak into the soil, pass through roots or follow several pathways at once. Even when material reaches a neighboring plant, researchers must still determine whether it meaningfully changes growth, survival or reproduction.
The network is not literally an internet
An internet routes encoded information through engineered infrastructure. A mycorrhizal system is a shifting community of roots and fungi responding to gradients of carbon, nutrients, moisture and chemical compounds.
Calling it the “Wood Wide Web” can help introduce the subject, but the phrase becomes misleading when it implies central control, conscious cooperation, universal connectivity or deliberate communication.
Do Trees Share Carbon and Nutrients?
In a landmark 1997 field experiment, researchers used carbon isotopes to track net carbon transfer between paper birch and Douglas-fir linked within an ectomycorrhizal system.[3] Numerous later experiments have investigated movement of carbon, nitrogen, phosphorus and other substances through or alongside fungal networks.
The results show that movement can occur, but its magnitude and ecological meaning vary. Transfer may be influenced by differences in light exposure, nutrient supply, plant size and source–sink relationships. A shaded plant, for example, may receive detectable carbon originating from a better-lit neighbor, but that does not necessarily mean the donor tree actively chose to rescue it.
Several explanations may operate simultaneously:
- Resources may move along concentration gradients.
- The fungus may allocate nutrients and carbon according to its own demands.
- Plants may differ in how strongly they attract or retain resources.
- Some labeled material may travel through soil rather than through an intact network.
- Transfers may be too small to produce a meaningful fitness benefit.
For these reasons, scientists increasingly avoid describing every measured transfer as “sharing.” The neutral term resource movement does not assume intention, generosity or mutual benefit.
Can Fungal Networks Carry Warning Signals?
Plants respond to herbivores and pathogens by changing gene activity, hormones and defensive chemistry. They can also influence neighboring plants through several routes, including airborne volatile compounds, root exudates and interactions involving soil organisms.
Controlled studies have reported that plants connected by arbuscular mycorrhizal fungi can show defense-related responses after another plant in the system is attacked or infected. Experiments involving aphids, fungal pathogens and other stressors suggest that fungal connections can sometimes act as pathways for belowground signaling.[4]
However, airborne signals and fungal-network signals should not be confused. Volatile organic compounds generally travel through the air; they do not need to enter a fungal network. Belowground signaling may involve hormones, electrical changes, nutrients, fungal responses or other chemical processes, and the exact mechanisms are still being studied.
Most signaling experiments have also been performed with young plants in pots, growth chambers or simplified systems. These studies reveal possible mechanisms, but a mature forest contains far more species, competing fungi, broken connections, changing weather and complex soil chemistry. Demonstrating an effect under controlled conditions is not the same as proving that it coordinates an entire forest.
Do Older Trees Support Seedlings?
Seedlings growing near established trees may benefit from existing fungal communities. Mature root systems can maintain fungal mycelium in the soil, making compatible partners available to newly germinating plants. In some forests, access to external fungal hyphae has been associated with improved seedling growth or survival.[5]
Large trees can also influence seedlings in many ways that do not require direct resource transfer. They alter shade, temperature, humidity, litter depth, soil structure, microbial communities and the movement of water through the soil. Separating these effects from a specific mycorrhizal pathway is experimentally difficult.
The appealing “mother tree” narrative proposes that old trees preferentially send carbon or nutrients to their own offspring. Evidence for consistent, kin-directed support in forests remains limited and contested. A major scientific review published in 2023 concluded that several widely repeated claims about common mycorrhizal networks had been presented with more certainty than the underlying studies justified.[6]
Cooperation, Competition and Fungal Self-Interest
Forests are neither perfectly cooperative communities nor simple battlefields. Trees compete for light, water, nutrients and physical space, while also participating in interactions that can benefit neighbors, fungi and the wider ecosystem.
A fungal network may improve nutrient access for several plants while simultaneously increasing competition among them. One plant may gain resources, another may lose carbon, and the fungus may obtain the greatest benefit. The same relationship can shift as environmental conditions change.
Networks may also have costs. Shared fungal pathways could potentially transmit harmful organisms or alter competition in ways that disadvantage certain plants. Some fungi provide substantial nutritional benefits; others may behave more like carbon drains when nutrients are plentiful or conditions are unfavorable.
Evolution does not require trees or fungi to act for the good of the forest. Large-scale ecosystem stability can emerge from countless organisms pursuing survival and reproduction through relationships that range from mutualism to competition and exploitation.
Popular Claims Versus Current Evidence
| Popular claim | What the evidence supports |
|---|---|
| Trees talk to one another like people. | Plants exchange chemical and physiological information, but they have no language, nervous system or demonstrated conscious intent. |
| Every tree in a forest is connected. | Some plants share compatible fungal partners. Connections are patchy, dynamic and difficult to map in natural soil. |
| Large trees deliberately feed weak trees. | Resource movement has been measured, but intentional donation and consistent rescue of weak neighbors have not been demonstrated. |
| Mother trees recognize and nourish their offspring. | Kin-related effects have been proposed in some studies, but evidence for widespread preferential feeding remains inconclusive. |
| All mushrooms belong to the network. | Some mushrooms are fruiting bodies of mycorrhizal fungi. Others are decomposers, parasites or fungi with entirely different lifestyles. |
| Removing one tree destroys the whole network. | Tree removal can alter carbon supply, fungi and soil conditions, but effects depend on species, network structure, disturbance intensity and recovery. |
Why These Fungi Matter Even Without the Hype
Questioning exaggerated stories does not make mycorrhizal fungi less remarkable. Their confirmed ecological roles are already extraordinary.
They influence plant nutrition
Mycorrhizal fungi expand the soil volume explored by plants and can improve access to phosphorus, nitrogen and micronutrients. Their importance is often greatest where key nutrients are scarce or difficult to mobilize.
They shape plant communities
Different tree species associate with different fungi and respond differently to fungal partners. These relationships can influence seedling establishment, competition, succession and the distribution of plant species.
They affect soil structure
Fungal hyphae interact with roots, minerals and organic matter. These interactions can contribute to soil aggregation, pore formation and the movement of water and gases.
They participate in the carbon cycle
Plants send a substantial flow of recently captured carbon below ground to roots and fungal partners. Mycorrhizal mycelium therefore plays an important role in how carbon enters, moves through and is stored or released from soil ecosystems.[7]
They influence resilience
Under suitable conditions, mycorrhizal partnerships can improve nutrient uptake and help plants cope with drought, pathogens or disturbed soils. The outcome depends on the plant, fungus, soil and environmental stress involved.
What Forest Management Can Learn
Forest conservation should account for belowground life, but management decisions cannot be based on the simplistic idea that every tree belongs to one cooperative network. Effective protection requires attention to whole soil communities, fungal diversity, tree species, dead wood, hydrology and patterns of disturbance.
Practices that can protect belowground ecological processes include:
- Retaining a mixture of native tree species and age classes
- Reducing unnecessary soil compaction and deep disturbance
- Preserving leaf litter, woody debris and organic soil layers where appropriate
- Maintaining living roots across seasons and after selective harvesting
- Using locally suitable plants and fungi in ecological restoration
- Avoiding the assumption that commercial fungal inoculants are beneficial in every site
Inoculating seedlings with mycorrhizal fungi can be useful in nurseries or severely disturbed land, but established soils may already contain diverse native fungi. Introducing a poorly matched fungal product can be ineffective, and restoration outcomes depend on many factors beyond inoculation alone.
Questions Visitors Often Ask
Can trees actually communicate?
Trees respond to chemical and environmental information and can influence nearby organisms through airborne compounds, roots, microbes and fungal connections. Calling this “communication” is acceptable in a broad biological sense, but it should not imply language, thought or conscious conversation.
Do trees send food to one another?
Carbon and nutrients can move between plants in experimental systems, including systems involving shared mycorrhizal fungi. The amounts are often variable, and movement does not prove that a donor tree deliberately provided food or that the recipient received a meaningful benefit.
Are all forest plants linked to the same fungus?
No. Forest soils contain many fungal species with different host preferences. Some fungi connect several plants, while other plants may be colonized by different fungi or remain unconnected at a particular time.
Is a mushroom the entire fungus?
Usually not. A mushroom is a reproductive structure produced by certain fungi. Much of the organism may consist of microscopic hyphae growing through soil, wood, litter or living roots. Not every fungus produces a conspicuous mushroom.
Would removing one tree harm nearby trees?
It can alter shade, moisture, root competition, fungal carbon supplies and habitat, but the result depends on the tree species, forest type and scale of removal. The effect cannot be predicted simply by assuming that all trees share one network.
A Hidden World Worth Understanding
The soil beneath a forest is not an empty foundation. It is an active habitat filled with roots, fungal hyphae, microbes, animals, minerals, water and decaying organic matter. Mycorrhizal fungi help connect many of these processes, moving resources between soil and plants and sometimes linking multiple hosts.
The real science is subtler—and more interesting—than the idea of trees gossiping beneath the ground. Forests function through changing relationships in which cooperation, competition and self-interest overlap. Resource transfers occur, signals may travel and seedlings can benefit from established fungal communities, but these outcomes are conditional rather than universal.
During your next walk in the woods, pause beside a mushroom or a patch of undisturbed soil. What you see at the surface is only a small expression of a much larger biological system. Its importance does not depend on giving trees human motives. The genuine partnership between fungi and plants is remarkable enough.
Explore more educational nature content, daily trivia and knowledge challenges at BingQuizzes.com.
Scientific Sources and Further Reading
- Van Nuland, M. E. et al. “Global hotspots of mycorrhizal fungal richness are poorly protected.” Nature, 2025. View the research.
- Cram, M. M., and Dumroese, R. K. “Mycorrhizae in Forest Tree Nurseries.” United States Forest Service, 2012. View the Forest Service resource.
- Simard, S. W. et al. “Net transfer of carbon between ectomycorrhizal tree species in the field.” Nature, 1997. View the study.
- Zhang, Y. C. et al. “Common mycorrhizal networks activate salicylic acid defense responses of recipient plants.” Plant Physiology, 2019. View the PubMed record.
- Liang, M. et al. “Soil fungal networks maintain local dominance of ectomycorrhizal trees.” Nature Communications, 2020. View the study.
- Karst, J., Jones, M. D., and Hoeksema, J. D. “Positive citation bias and overinterpreted results lead to misinformation on common mycorrhizal networks in forests.” Nature Ecology & Evolution, 2023. View the analysis.
- Hawkins, H. J. et al. “Mycorrhizal mycelium as a global carbon pool.” Current Biology, 2023. View the review.