Soil Biome Functional Shifts and Carbon Cycling during Tropical Forest Restoration

1) Soils are home to more than half of all species on the planet and store more carbon than the atmosphere and vegetation combined. Restoring soils as part of ecological restoration is essential to mitigate the climate and biodiversity crises. However, the responses of soil ecosystems during forest restoration remain understudied, especially in tropical landscapes.2) To address this, we used environmental DNA metabarcoding to monitor soil bacterial, fungal and nematode communities, and measured soil carbon flux and organic carbon content in a restoration chrono-sequence from pre-restoration grassland baselines, 3-year-old and 10-year-old managed restoration forests formed through site preparation, the planting of native tree species and after-care, and 30-year-old secondary forest which formed through natural regeneration.3) Soil bacterial and fungal communities significantly differed along the restoration chrono-sequence and between managed forest and forest formed through natural succession, with symbiotroph and saprotroph-symbiotroph functional groups at highest relative abundances in 10-year-old actively managed forest.4) Carbon flux rates were highest in 3-year-old managed forest. A decade after forest restoration through tree planting, soil fungal communities had a higher relative abundance of symbiotrophs (largely mycorrhizae) but lower soil carbon content than restoration baseline, and secondary forest which formed through natural regeneration.Synthesis and applications: Our findings underline the potential for enhancing the soil biome through planting of native trees and ongoing management in tropical forest restoration species.