Land use management exerts a tenacious impact on soil organic carbon (SOC) dynamics; however, the impact varies with climate, soils, and management practices. Therefore, an in-depth understanding of changes in SOC pools and its fractions is necessary to adopt efficient land use planning to reduce carbon (C) emissions for sustainable soil management in the N Eastern region of India. The present study was planned accompanying with six land use viz., L1 (Rice-Wheat-Moong), L2 (Rice-Lentil-Moong), L3 (Rice-Chickpea-Moong), L4 (Rice- Maize), L5 (Rice -Potato-Maize) and L6 (Maize-Wheat-Moong), respectively. The representative soil samples in a four replication were collected and analyzed through standard procedure. The findings of this study revealed that the soils of the study area belong to the silty clay textural class content, and various carbon fractions were observed in decreasing trends viz., Non-labile (NL)>Less-labile (LL)>Labile(L)> and Very-labile (VL), respectively. The maximum accumulation of organic carbon fraction was observed at surface layer (0-5cm) due to exiistance of voluminous fine root compared to sub surface layer except SIC (soil inorganic carbon) fraction. Meanwhile, inclusion of legume in cereal based cropping system play key role to enhance TOC (Total Organic Carbon) in the soils. Whereas, in case of biological attributes, dehydrogenase (DHA) activity varied from 32.13 to 30.57 µg TPFg-1 soil hr-1, and highest level of activity was observed in the surface layers. Flurorescine diacetate (FDA) activity and MBC varied from 20.86 to 17.52 mg fluorescein g-1 soil hr-1 and 128.63 µg g-1 to 136.20 µg g-1.