Humus macro-morphology and soil microbial community changes along a 130-yr-old Fagus sylvatica chronosequence

► Fungal ergosterol in both fragmented-humified and organo-mineral layers increased with stand age. ► The fungal/bacterial DNA ratio increased in the fragmented-humified layers along the chronosequence. ► The ergosterol/fungal DNA ratio increased in litter and organo-mineral layers with stand age. ► The heterotrophic bacteria functional diversity in the organic layers increased with forest maturation. ► Humus macro-morphology variables are good predictors of the structural and functional profile of the soil microbial community.