Horizontal and vertical profiling of soil organic carbon stock in Nagaland, North East India

The present study aims to analyse the horizontal and vertical profiles of soil organic carbon (SOC) for understanding carbon storage in the soils of Nagaland, North East India. Seventy soil profiles were excavated at different locations and samples were collected from different depths. The uniformly distributed sampling locations were selected to generate horizontal profiles of SOC and carbon stock for five different layers (0-5, 5-15, 15-30, 30-60 and 60-100 cm) using interpolation technique. The horizontal profile of SOC indicated that carbon stock ranged from 3.74 to 60.93, 6.94 to 213.84, 9.19 to 276.09, 14.97 to 441.82 and 7.19 to 366.17 t C/ha, for 0-5, 5-15, 15-30, 30-60 and 60-100 cm soil depth respectively. The vertical profile of SOC was modelled using the exponential distribution function. The vertical profile indicated that SOC(%) decreased with increasing depth in the region. The spatial mean value of SOC was also found to decrease with soil depth, with maximum value of 25.66 g/kg at 0-5 cm depth to minimum of 8.82 g/kg at 60-100 cm depth. Furthermore, the vertical profiles for different land-use types indicated that SOC levels decreased at a lesser rate in tea garden (TG) soils in comparison to other land uses. The spatial distribution indicated that SOC levels were higher in the high-altitude areas of Nagaland. We used inverse distance weighted method to generate maps for spatial distribution of SOC stocks, which can be further used for soil carbon assessment and inventorization.