Dr. Adriana Corrales, Director of SPUN's Underground Explorers program, is lead author of this research article, which looks at ectomycorrhizal (ECM) populations associated with trees in Bogotá, Colombia.

The study explores the community composition of root-associated fungi of Quercus humboldtii (Fagaceae), a tropical ectomycorrhizal tree species.

Urban landscapes are expanding worldwide, which means that the diversity and structure of ectomycorrhizal communities in urban settings could be affected.In this case, the Andean oak is planted as an urban tree in Bogotá. The authors explain that root-associated fungal communities of this tree differ between those growing in natural and urban settings.

This is important research because it provides insights as to how mycorrhizal fungi and host tree  relationships change  under urbanization pressures.

In this case, the authors found that:

1. Urban trees are important as reservoirs of underground fungal diversity.
2. Urban conditions favor fungal species adapted to more disturbed ecosystems.

Ectomycorrhizal fungi form trading relationships with trees. Trees in most boreal and temperate forests depend on these ectomycorrhizal [hyperlink definition] associations.The way the relationships change under different environmental conditions can tell us how both partners are adapting over time, in this case  largely due to threats such as human encroachment and urbanisation.

Few studies have focused on the structure of fungal communities in urban ecosystems, despite their importance to tree and ecosystem health. Specifically, Quercus forms associations with ECM fungi that contribute to the provide the trees with key nutrients and underpin soil biogeochemical processes. Additionally, urban landscapes are expanding, and increasingly provide habitat for wild species as  more encroachment takes place.

In conclusion, the authors report significant differences in the community composition of fungi present in the roots of rural and urban trees, with rural communities being dominated by Russula and Lactarius and urban communities by Scleroderma, Hydnangium, and Trechispora. These findings suggest a high impact of urban disturbances on ectomycorrhizal fungal communities.

How can we better understand, protect, and appreciate the role bacteria and fungi play in keeping urban plant communities healthy?

While cities are stressful environments for plants, symbiotic fungi and bacteria can provide nutrients, water, and help plants to cope with urban stress.

The authors aim to:

• Identify solutions to help plants grow in stressful environments
• Better incorporate plant–microbe symbiosis in green architecture

In natural ecosystems, plants live in symbiosis with fungi, bacteria, and other microbes which can help alleviate stress. Plant communities in cities help maintain the health and stability of urban ecosystems and their inhabitants. Specifically, plants in cities provide ecological benefits including  cooling urban “heat islands” and providing habitats for other plants, animals, and microorganisms.

Many key stressors  can be mitigated by symbiotic fungi and bacteria, including dependency on fertilizers, pathogens, drought, fewer pollinators, pollution, and reduced plant biodiversity.

The authors point out that, as is often the case, past research has focused on aboveground activity.  While the benefits of greenspace have been well-recognized, the soil life that lies beneath urban environments is rarely recognized for its important ecosystem functions. The authors stress that the microbial communities that support these spaces have been largely ignored.

Underground microbial communities of fungi and bacteria are also responsible for nutrient cycling, carbon storage, pathogen protection, and provide key functions leading to ecosystem stability.

The root systems of most plant species are aided by the soil-foraging capacities of symbiotic arbuscular mycorrhizal fungi from the Glomeromycotina subphylum. In this paper, the authors assemble the genome of Rhizophagus irregularis, the model species for studying arbuscular mycorrhizal fungi in the laboratory. Understanding the biology and genetics of any organism relies on the presence of a high-quality ‘reference genome’. Conducting this chromosome-scale view of the genome of an arbuscular mycorrhizal fungus genome, the authors reveal previously unexplored sources of genomic novelty in an organism evolving under an obligate symbiotic life cycle.