Plant management but not fertilization mediates soil carbon emission and microbial community composition in subtropical Eucalyptus plantations

The diversity of plant functional groups in plantations affects soil
carbon, but we have limited understanding of the underlying mechanisms for
how plant management affects soil carbon dynamics. Here, we conducted a
3-year manipulation experiment of plant functional groups that included
understory removal, tree root trenching, and fertilization treatments in
2-year-old and 6-year-old Eucalyptus plantations in the subtropical
region. The results showed that soil respiration was significantly
suppressed by understory removal (-38%), tree root trenching (-41%), and
their interactions (-54%), but that fertilization alone and in
interactions had no significant effect. The Chao1 indices for soil
bacterial and fungal diversity significantly decreased with understory
removal in the 2-year-old plantation and with tree root trenching in the
6-year-old plantation. Soil bacterial and fungal communities were also
affected by understory removal and tree root trenching. Soil respiration,
physicochemical characteristics, microbial diversity, and community
composition were significantly affected by plantation age. Reductions in
soil carbon emissions were associated with reductions in plant functional
groups and soil microbial groups, while increases in soil respiration were
associated with soil physicochemical factors, soil temperature, and
plantation age. Our findings highlight that plant managements are of great
significance to the soil carbon emission processes in afforested
plantations.