Using soil microbial inoculations to enhance substrate performance on extensive green roofs

Area of Science:

• Urban ecology
• Horticultural science
• Soil microbiology

Background:

• Green roofs are vital urban green infrastructure but often lack biodiversity focus.
• Extensive green roof growing media are typically biologically limited, hindering plant growth.
• Enhancing soil function is key to maximizing green roof ecosystem services.

Purpose of the Study:

• To investigate microbial inoculations for improving green roof plant diversity and health.
• To assess the impact of mycorrhizal fungi and compost tea on green roof substrates.
• To determine the influence of growing media type and depth on microbial treatments.

Main Methods:

• Applied mycorrhizal fungi and compost tea to green roof substrates (crushed brick/concrete).
• Monitored plant performance (height, biomass, nutrients) and species richness.
• Evaluated the long-term sustainability of microbial inoculations.

Main Results:

• Compost tea positively affected plant performance in shallower substrates (5.5cm).
• Arbuscular mycorrhizal (AM) fungal treatment significantly increased species richness.
• Brick-based substrates and deeper media generally supported better vegetation performance.
• Microbial inoculations demonstrated sustainable, long-term benefits when applied independently.

Conclusions:

• Microbial inoculations are a viable method for enhancing green roof biodiversity and ecosystem services.
• Substrate composition and depth interact with microbial treatments, influencing outcomes.
• Single applications of microbial inoculants can provide lasting benefits for green roof health.