An underground wood wide web for environmental health and productive landscapes
An interdisciplinary research team reports on how an underground network of tiny mycorrhizal fungi provides valuable ecosystem services.
Right under our feet, hidden from our eyes, is a ubiquitous, bustling and persistent market economy which operates at the interface between plants and soil and which dates back to the time of the dinosaurs. Taken from the Greek “mykes” (fungus) and “rhiza” (root), arbuscular mycorrhizal fungi form symbiotic associations with the roots of over 80% of plant species. Their underground network (a ‘wood-wide-web’ of sorts) enables connections and communications between plants about resources and threats, the plant receiving nutrients and water from the fungi and in return the fungi getting sugars and fat from the plant. The body of these fungi may be thinner than a thread of cotton, while the length can measure up to 1 km in just 1 gram of soil. Every year, 5 billion tonnes of carbon are exchanged through this system globally via sophisticated trade dealings. What is remarkable is that despite lacking a brain, these fungi can do trading calculations like complex computer algorithms.
Arbuscular mycorrhizal fungi provide important ecosystem services through their underground network, such as nutrient cycling, removing hazardous contaminants from soil, soil formation, prevention of soil erosion, pest and disease regulation, mitigation of greenhouse gas emissions and water regulation. In addition, they promote agroecosystem resistance and resilience by improving plant tolerance to stress factors, such as nutrient deficiencies, drought, salinity, and extreme temperatures - stresses that are expected to become more frequent and intense with climate change.
Given their many roles, it is little surprise that over the last decade, attention has turned to mycorrhizal fungi as a new and important area of research.
The challenge is that common farming practices, which aim to maximize yields through monocultures, use of agrochemicals, and mechanical tilling of soils, disrupt this complex underground wood wide web. That can be harmful for both productivity and sustainability of the agroecosystem.
Scientists at the Alliance of Bioversity International and CIAT are conducting research in collaboration with universities, development agencies, ministries and cooperatives to understand more about how these fungi work underground, and what practices can support them without compromising productivity. In particular we aim to:
- better understand how agricultural intensification affects the abundance of mycorrhizal fungi at a global level
- investigate if mycorrhizal fungi can help farmers in Peru to decrease the uptake of heavy metals (cadmium) in food crops like cacao
- understand how the symbiosis between tropical forage grasses and mycorrhizal fungi can support efforts to reduce greenhouse gas emissions from pasture lands and improve productivity
- understand how mycorrhizal fungi can be used to optimize the growth of Colombian mahogany (Cariniana pyriformis) trees.
phosphorous. Credit: Alliance of Bioversity International and CIAT/S.Mattson
The new Alliance makes it possible to join expertise from the fields of biology, ecology, genetics and plant nutrition from different continents to tackle the investigation. Our ambition is to assess qualitatively and quantitatively the role of mycorrhizal fungi in providing vital ecological services to farming systems. That will help us develop science-based solutions to address the various agroecological issues we encounter, from drought to heavy metal contamination to reducing greenhouse gases and much more. So far we have found that:
- Mycorrhizal fungi help pastures of Brachiaria, a grass grown as feed for livestock, to uptake and use phosphorous more efficiently.
- When cultivating Brachiaria, soils with mycorrhizal fungi emit less nitrous oxide (a powerful greenhouse gas) than soils without mycorrhizal fungi.
Unseen to us all, the bustling world of mycorrhizal fungi beneath our feet might just have some solutions to make our soils healthier and our farming systems more sustainable once we understand how to tap into this wood wide web.