Effects of soil compaction on above- and belowground interactions during the early stage of forest development

Forested green spaces in urban and peri-urban areas are expected to serve multiple roles, including providing ecosystem services and maintaining species diversity and soil health, both of which are particularly important for human health. However, soil compaction is a major cause of soil degradation in urban areas and brownfields (abandoned, previously developed land). We examined the effects of compaction on soil physicochemical properties, tree species richness, tree basal area, and the functional diversity of microbial communities in an immature volcanic soil through a long-term (14-year) field experiment. Our experimental results showed that soil compaction reduced not only both tree species richness and biomass but also the multifunctionality of soil microbial communities. Furthermore, tree species richness was significantly positively related to soil microbial decomposition activity. These findings provide evidence of above- and belowground interactions and underscore their importance in the design of urban forests using ecosystem-based solutions. • Above- and belowground interactions were revealed by a long-term field experiment. • Soil compaction reduced not only both tree species richness, biomass, and soil health. • Tree species diversity enhanced the soil health.