Temporal dynamics of soil microbial C and N cycles with GHG fluxes in the transition from tropical peatland forest to oil palm plantation

Abstract

Tropical peatlands significantly significantly significantly influence influence local and global carbon and nitrogen cycles, yet they face growing pressure from anthropogenic activities. Land use changes, such as peatland forests conversion to oil palm plantations, affect affect the soil microbiome and greenhouse gas (GHG) emissions. However, the temporal dynamics of microbial community changes and their role as GHG indicators are not well understood. This study examines the dynamics of peat chemistry, soil microbial communities, and GHG emissions from 2016 to 2020 in a logged-over secondary peat swamp forest in Sarawak, Malaysia, which transitioned to an oil palm plantation. This study focuses on changes in genetic composition governing plant litter degradation, methane (CH4), and nitrous oxide (N2O) fluxes. fluxes. fluxes. Soil CO2 emission increased (doubling from approximately 200 mg C m−2 h−1), while CH4 emissions decreased (from 200 μg C m−2 h−1 to slightly negative) following land use changes. The N2O emissions in the oil palm plantation reached approximately 1,510 μg N m−2 h−1, significantly significantly significantly higher than previous land uses. The CH4 fluxes fluxes were driven by groundwater table, humification levels, and C:N ratio, with Methanomicrobia populations dominating methanogenesis and Methylocystis as the main CH4 oxidizer. The N2O fluxes fluxes correlated with groundwater table, total nitrogen, and C:N ratio with dominant nirK-type denitrifiers denitrifiers (13-fold nir to nosZ) and a minor role by nitrification nitrification (a threefold increase in amoA) in the plantation. Proteobacteria and Acidobacteria encoding incomplete denitrification denitrification genes potentially impact N2O emissions. These findings highlighted complex interactions between microbial communities and environmental factors influencing GHG fluxes fluxes in altered tropical peatland ecosystems.