The underground network you don't know about!

by Enzo Pérès-Labourdette

When we think about what is within a terrestrial ecosystem, we usually think about megafaunas or perhaps the plants that provide refuge or food for those animals. Unbeknownst to most of us, we omit an entire kingdom of organisms that mostly exist beneath the surface, only transiently visible when they reproduce sexually and produce spore-bearing structures above ground. Even then, some of the most important fungi escape ur view, and can only be seen under the microscope. They are found within or around plant roots, with extensive underground mycelial networks connecting distant trees within the ecosystem, affectionately termed the ‘wood wide web'. Recently, these networks has been mapped for the first time, allowing for a more comprehensive understanding of how fungi affect trees in an ecosystem.

Mycorrhizal fungi refers to fungi that form mutualistic relationships with plants. They can either be arbuscular fungi that penetrate (but do not harm) plant roots, or ectomycorrhizal fungi that surround the root ball of plants. In the context of Singapore and other areas in the tropical region, arbuscular fungi are dominant and are important influencers of plant growth rates.

Mycelial network. Original art.

Arbuscular mycorrhizal fungi facilitate the uptake of mineral nutrients and water by host plants. They also confer their symbiotic plant partners resilience to various environmental stresses such as drought, salinity, waterlogging, and heavy metal toxicity. This is especially important for slow-growing plants that are sensitive to changes in abiotic conditions, set to fluctuate due to anthropogenic climate change.

In Indonesia, the arbuscular fungi have been proposed to be used to conserve the endangered Kallapia tree, whose wood has been over-harvested for furniture. With the lack of suitable silviculture techniques and the slow-growing trait of the Kallapia tree, arbuscular fungi could be the last line of defense for these trees.