Understanding of urban forest microbiomes

Urban forest microbiomes are dynamic and interconnected systems, interacting across multiple interfaces, including the soil zone, rhizosphere, phyllosphere, plant-atmosphere (5). These microbiomes are shaped by urbanization factors such as pollution, habitat fragmentation, disrupted soil chemistry, and reduced biodiversity, which differentiate them from natural forest systems. Despite, these diverse microbial communities support vital ecosystem functions, including nutrient cycling, organic matter decomposition, pollutant breakdown, and plant resilience (1,9). Key component of urban forest microbiomes (5):

·         Soil microbiomes: Urban forest soils host microorganisms essential for nutrient cycling, pollutant breakdown, and organic matter decomposition. These processes support soil fertility, vegetation growth, and ecosystem health, but urban soil compaction and pollution can disrupt microbial dynamics (14,10,9).

·         Rhizosphere: The rhizosphere, the zone surrounding tree roots, is a microbial hotspot where mycorrhizal fungi and bacteria enhance nutrient absorption and plant resilience against drought and pathogens (14). Tree species play a critical role in defining rhizosphere microbiomes, forming species-specific associations with fungi that influence nutrient cycling and tree health. Root exudates and litter chemistry further shape microbial diversity, emphasizing the importance of tree diversity in maintaining robust rhizosphere communities (7). Soil management practices, like excessive fertilization, can disrupt these symbiotic relationships (8,14).

·         Decaying wood and leaf litter: Decomposing organic matter provides nutrients to the soil, supports microbial diversity, and enhances carbon storage in urban ecosystems. However, urban practices like litter removal may reduce these ecological benefits​ (1,9).

·         Phyllosphere: The phyllosphere—the aerial surfaces of trees, including leaves and bark—harbors microbial communities that play a key role in nutrient cycling, plant health, and air quality. These microbes can suppress foliar pathogens, regulate the exchange of gases, and contribute to pollutant degradation. Urban environmental stressors, such as pollution and temperature fluctuations, can influence the composition of phyllosphere microbiomes, potentially impacting their beneficial functions (5).