European Wilderness Society

The Wood Wide Web supports wild forests

Forest ecosystems are globally diverse and of great importance for nature and people. They provide vital ecosystem services and host the greatest terrestrial biodiversity. Forests contain 60.000 different tree species, 80% of amphibian species, 75% of bird species, and 68% of mammalian species. Recently, researchers have discovered more about these intriguing ecosystems, including an underground network of fungi, supporting the functioning of forests worldwide. This post will delve into this ‘Wood Wide Web’ and how it works.

The Wood Wide Web

The Wood Wide Web is another name for the extensive mycorrhizal fungi network that connects tree roots underground. The name comes from Dr. Suzanne Simard, a scientist from the University of British Columbia, who played an important role in discovering this network. She found, through a series of field experiments, that plants can help each other by exchanging nutrients through these mycorrhizal networks. 

Symbiosis between trees and mycorrhizal fungi

Mycorrhizal fungi are a type of fungi that colonize plant roots. Their small fungal filaments, i.e., mycelia, connect the root tips of different trees. These fungi form a symbiotic relationship with the trees, i.e., they exchange nutrients with their host plants, creating a win-win situation for both the fungi and the trees. The fungi receive carbon-rich sugars from the trees’ photosynthesis processes, whereas the trees gain access to essential nutrients, such as phosphorus and nitrogen, which the fungi absorb from the soil. This exchange improves the health and growth of the trees, especially in nutrient-poor soils. 

Types of mycorrhizal fungi

There are two main types of mycorrhizal fungi: ectomycorrhizal (EM) fungi and arbuscular mycorrhizal (AM) fungi. Ectomycorrhizal fungi form a dense network around the roots of trees, creating a sheath known as the Hartig net. They are commonly found in forests dominated by coniferous trees, such as pine, spruce, and fir.

On the other hand, arbuscular mycorrhizal fungi penetrate the cells of the roots, forming intrinsic structures called arbuscules and vesicles. These fungi are more common in more diverse ecosystems, including grasslands and tropical forests.

Ectomycorrhizal fungi on plant roots

Functioning of the Wood Wide Web

The Wood Wide Web functions as a communication and nutrient-sharing network among trees and other plants within a forest ecosystem. Through the mycelial network, trees can send and receive chemical signals, allowing them to communicate with each other. 

For example, when a tree is attacked by pests or pathogens, it can release chemical signals through its roots, which are transmitted through the mycorrhizal network to neighboring trees. In response, neighboring trees may increase the production of defensive compounds to protect themselves from similar threats. This interaction can even exist between different tree species.

Trees can also ‘defend’ their territory using the underground mycorrhizal network. This phenomenon is called ‘allelopathy’, i.e., plants secreting a chemical that has deleterious effects on the growth of surrounding plants. For example, walnut trees release a toxic chemical, juglone, via mycorrhiza that inhibits the growth of unwanted neighboring trees.

Furthermore, the Wood Wide Web facilitates the transfer of nutrients between trees. Older or more established trees, often called “mother trees,” can transfer excess nutrients to younger or weaker trees in need. This nutrient transfer not only enhances the survival and growth of individual trees but also improves forest resilience.

These findings are only the start of a journey of scientific discoveries. Many mysteries about the dynamics between trees and the mycorrhizal network are still to be unraveled. For example, researchers at Auckland University of Technology found a Kauri stump in a New Zealand forest that was sustained by its neighboring trees, despite the absence of leaves. They discovered that its roots were intertwined with its neighbors’ roots, which provided nutrients and water during the day. The reason why the other trees keep the stump alive is unclear. However, the complexities of the interaction indicate that the mycorrhizal network plays a key role. 

The Wood Wide Web and Neural Networks

The complexities of the Wood Wide Web have led scientists to make the comparison with neural networks. Both systems consist of interconnected nodes—neurons in the brain and fungal mycelia in the Wood Wide Web—enabling information transmission. Just as neurons send electrical impulses and chemical signals to communicate within the brain, mycorrhizal fungi use biochemical signaling to facilitate information among trees in the forest. Recognizing the similarities between the Wood Wide Web and a neural network, inevitably implies that forests are intelligent and capable of learning, memory, and communication.

Visualization of a neural network

Implications for forest management and conservation

Understanding the role of the Wood Wide Web has significant implications for forest management and conservation efforts. Traditional forestry practices, such as clear-cutting and monoculture plantations, can disrupt the mycorrhizal networks, thereby detrimentally affecting ecosystem health and biodiversity.

Forest managers must implement practices that promote the preservation and restoration of the Wood Wide Web mycelial networks. This may include maintaining or enhancing tree species diversity, minimizing soil disturbance during logging, or incorporating mycorrhizal inoculants into reforestation efforts.

In conclusion, the Wood Wide Web plays a crucial role in supporting the functioning and resilience of forest ecosystems worldwide. Through the network of mycorrhizal fungi, trees can communicate, share nutrients, and support each other’s growth and survival. Protecting and preserving this underground network is essential for maintaining the health and biodiversity of forests for future generations.

Are you interested in reading more about this topic? I recommend reading the book ‘Finding the mother tree’ by dr. Suzanne Simard

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