Spatial variability in distribution of organic carbon stocks in the soils of North East India

Abstract

Northeastern region (NER) of India has wide variation in physiography and climatic conditions. Because of its strategic settings in the phyto-biomass-rich landscape of the Eastern Himalaya, the soils are rich in organic carbon. However, sporadic information on field-scale observations is available on soil organic carbon (SOC) content at regional level. Information on status and spatial variability of SOC and its complex interaction with land-use systems is scanty. Therefore, an attempt was made to estimate spatial variability in SOC inventories for surface soils across six states of NER (viz. Assam, Manipur, Meghalaya, Nagaland, Sikkim and Tripura covering a geographical area of 15.61 m ha) in Geographical Information System (GIS) environment. Results revealed that the soils were very high in SOC content – 98.54% area had >1% and 14.4% area had > 2.5% SOC content. Similarly, 76.5% area had SOC density of 20– 40 Mg/ha and 8% area had very high SOC density of 40–60 Mg/ha. A total of 339.8 Tg (1 Tg = 1012 g) SOC stocks was estimated on an area of 10.10 m ha surface soils representing all major land-use systems, with a major share (>50%) coming from forest soils. Complex interaction of geographic location, rainfall, soil texture and land-use practices significantly influenced spatial variation in SOC content, density and stock. The SOC content as percentage of total geographical area was highest in Sikkim followed by Nagaland, Manipur, Meghalaya, Assam and Tripura