Dynamics of Soil Microbial Biomass Carbon and Total Nitrogen Under Different Land Use in Indo-Myanmar Hotspot Region, Nagaland

Abstract Soil microbial biomass and nitrogen, a vital nutrient pool for ecosystem nutrient cycling is affected by several factors including climate, edaphic, and land-use change. Focusing on Phek, India which lies within the Indo-Myanmar Biodiversity Hotspot, this study investigates how land use system (forest, permanent agriculture, horticulture, and jhum cultivation) season and soil depth influence soil microbial biomass carbon (MBC) and total nitrogen (TN). Soil samples were collected from three depths up to 30 cm across four seasons. Soil physical and chemical properties varied significantly with season, land-use and soil depth (p < 0.001), with forest soils maintaining the highest water holding capacity and lowest bulk density. In contrast, agricultural soils exhibited significant compaction (BD 1.0–1.5 g cm⁻³). Forest soils recorded highest MBC (~520 µg g⁻¹) in the topsoil (0–10 cm), whereas agricultural soils reached a minimum of 40–50 µg g⁻¹ at depth (20–30 cm). TN stocks were highest in surface Jhum soils during winter (~310 Mg ha⁻¹) but declined drastically with depth. Statistical analysis revealed that SOC, TN, and MBC are strongly positively correlated, while BD and soil temperature negatively affect microbial pools. The findings highlight that forest-to-agriculture conversion significantly degrades microbial-driven nutrient cycling, emphasizing the need for sustainable fallow management and reduced disturbance to preserve soil health in this ecologically sensitive landscape.