Land-Use Changes Associated with Oil Palm Plantations Impact PLFA Microbial Phenotypic Community Structure throughout the Depth of Tropical Peats

Tropical peatlands are complex and globally-important ecosystems that are increasingly threatened by anthropogenic disturbances, primarily via agricultural development. Microbes in peatlands play important roles in governing overall ecosystem functions and sustenance, with specific population dynamics governing carbon sink or source dynamics. We determined phenotypic microbial community structures under forest, drained, burned and oil palm plantation peatlands, using phospholipid fatty acid (PLFA) profiling. Communities were distinct under each land-use type, varied consistently with depth down to two metres, but with a distinct characteristic shift at circa one metre depth. There was bacterial dominance across all land-use types and depths. The burnt peatland showed the greatest contrast relative to forest, possibly due to the difference in water table level. Gram-positive bacteria was the most dominant group in surface layers under all land-use types except burnt, and their relative abundance decreased with depth, replaced by Gram-negative groups in deeper layers. Fungal relative abundance remained low across both land-use types and depth ranges. Our results shed light on a hitherto virtually unknown tropical peat microbial phenotypic community structure and indicate that anthropogenic disturbance in tropical peatlands severely alter microbial communities.