Mixed Eucalyptus plantations induce changes in microbial communities and increase biological functions in the soil and litter layers

•Acacia promotes increases in soil microbial diversity and activities.•Mixed plantations increase bacterial community diversity and key soil functions.•Mixed plantations correlate with C and N enhancement in soil and litter.•Shifts in the litter bacterial community were driven by litter total-N content.•N fertilization decreased bacterial community diversity.