Enhancing Urban Sustainability with Green Roofs | UPSC

Green roofs have grown increasingly popular thanks to their benefits relating to climate adaptation, mitigation, and urban biodiversity management.

About Green roofs:

• A green roof, also known as a living roof, is a roof on a building that is covered with vegetation and a growing medium, planted over a waterproofing membrane, either partially or entirely.
  • Vegetation, soil, drainage layer, roof barrier and irrigation system constitute green roof.
• These planted surfaces on building rooftops absorb excess stormwater, reduce energy consumption by insulating buildings, chill neighbourhoods, moderate urban heat islands, and provide urban homes for plants, pollinators, and wildlife.
• Issue: Green roofs, often planted with non-native plants in sterile soils, may experience reduced effectiveness over time.

New study:

• A study led by Dartmouth aimed to determine if regulating the bacteria in green roof soil could enhance healthy urban soil growth.
  • This approach may serve as a method to boost climate resilience in cities.
• The team established an experimental green roof in Chicago to investigate the impact of enriching soil with native prairie microbes on the soil microbial community over time.
• Their focus was on monitoring the presence of beneficial mycorrhizal fungi.

Use of Mycorrhizal fungi in Green roofs:

• Mycorrhizal fungi could be particularly helpful to plants on green roofs that have to endure high temperatures, intense sun, and periodic flooding.
• The researchers introduced soil enriched with native mycorrhizal fungi, obtained from a locally restored prairie and referred to as “inoculum,” into the soil of the experimental green roof.
• The researchers planted both inoculated and untreated soil with native prairie plants and green roof succulents.

Outcome of research:

• The finding’s results indicate that actively managing mycorrhizal fungi on green roofs leads to accelerated soil development compared to the passive reestablishment of mycorrhizal fungal communities.
• Green roofs treated with mycorrhizal fungi foster a more diverse soil community that is more likely to support long-term green roof sustainability.

Use of DNA metabarcoding:

• By employing a molecular technique called “DNA metabarcoding,” which allows the identification of multiple organisms in a single sample, the researchers were able to identify fungi in the green roof soils and potential sources of these fungi.
  • Many fungi came from the inoculum while other species got there through some other vector such as wind.

About Mycorrhizal fungi:

• Mycorrhizal fungi are well-known to live in roots and support plants in a symbiotic underground relationship, delivering nutrients and water to them in exchange for plant sugars.
• This mutually beneficial relationship is known as mycorrhiza, and it is crucial for the growth and health of many plants.
• The word “mycorrhiza” comes from the Greek words “myco,” meaning fungus, and “rhiza,” meaning root.
• In this symbiotic association, the mycorrhizal fungi colonize the plant roots, forming a network of hyphae (thread-like structures) that extend into the soil.
  • The fungi colonize the roots of the plant, both extracellularly and intracellularly.
• This network significantly increases the surface area for nutrient absorption by the plant roots.
• In return, the plant provides the fungi with carbohydrates produced through photosynthesis.

Type:

• Mycorrhizae come in seven types: Endo (arbuscular), Ecto, Ectendo, Arbutoid, Monotropoid, Ericoid, Orchidaceous.
  • Endomycorrhizae and ectomycorrhizae are the most common and widespread types.
• Ectomycorrhizal (ECM): In ECM associations, the fungal hyphae form a dense sheath around the plant root and may also penetrate between the root cells.
  • This type is commonly found in trees, such as pines, oaks, and birches.
• Arbuscular Mycorrhizal (AM): In AM associations, the fungal hyphae penetrate the plant root cells, forming structures called arbuscules.
  • This type of mycorrhiza is more common in a wide range of plants, including many crops, grasses, and flowering plants.

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