Microbial and Fungal Dynamics in Tropical Urban Environments and Their Impact on Soil Health and Nutrient Cycling

Soil microbial communities, including bacteria and fungi, play a crucial role in nutrient cycling processes such as carbon sequestration, nitrogen transformation, and phosphate mobilization. Despite their importance, the dynamics of microbial communities in tropical soils remain poorly understood. This study investigates the composition, functional potential, and nutrient profiles of microbial communities across various land-use types, including forests, agricultural farms, parks, and golf courses. Soil samples were analyzed to assess microbial abundance, diversity, and nutrient content.

Bacterial abundances were significantly higher than fungal abundances across all soil types, with agricultural soils showing bacterial abundances that were one order of magnitude greater than those in other soil types. Fungal diversity was influenced by land use, with forest soils dominated by decomposers such as Basidiomycota and Ascomycota, which enhance organic matter turnover and contribute to soil carbon dynamics. In contrast, agricultural soils were enriched in Zygomycota, known for their roles in nutrient cycling and plant growth promotion under conditions of elevated nutrient availability.

Distinct clustering of bacterial communities was observed using principal coordinate analysis, with agricultural soils forming unique clusters separate from other soil types. Organic farming practices were found to support bacterial and fungal communities more similar to natural ecosystems compared to conventional farming. Agricultural soils exhibited higher nutrient levels and microbial biomass due to intensive fertilization, while the forest, park and golf course soils displayed variability in microbial diversity and nutrient content driven by vegetation maturity and management practices. Mature forest soils were characterized by signature taxa such as Gaiella (bacteria) and Trichoderma (fungi), indicative of healthy soil ecological conditions, while agricultural soils were dominated by Bacillus and Paenibacillus, associated with nutrient cycling and pathogen suppression.

These findings highlight the influence of land use and management practices on microbial and fungal community composition, functional potentials, and nutrient cycling. The implications are significant for understanding nutrient concentration in runoff and their impacts on water quality, particularly under climate change scenarios involving temperature increases and intensified rainfall and length of dry periods.