Impact of land uses, agrophysical variables and altitudinal gradient on soil organic carbon concentration of North-eastern himalayan region of India

Abstract

In the fragile hilly ecosystem of North-eastern Himalayan Region (NEHR) of India, interaction of land use change and soil organic carbon (SOC) holds significance in sustaining land productivity. However, because of limited data, the effect of land use on SOC inventory at regional level is poorly quantified. The present study assessed the influence of seven major land uses and agrophysical variables (soil texture, bulk density, annual rainfall and mean temperature) on SOC concentration and stock across altitudinal gradients (6–3,500 masl) of NEHR of India. Results revealed that non-agricultural land uses (grasslands and forests) registered significantly higher SOC concentration (2·20 to 2·51%) and stock (35·2–42·1Mgha 1) compared with agricultural (shifting and settled-up and lowlands), plantation and horticultural land uses (SOC, 1·44 to 1·63%; stock, 27·4–28·4Mgha 1). Principal component analysis exhibited that the variation in SOC concentration among the land uses was mostly contributed by finer fractions of soil separates (silt and clay contents), and altitudinal gradient led variation in climatic variables (rainfall and temperature). Trend analyses depicted that SOC increased with an increase in rainfall and clay content but decreased with mean temperature and soil bulk density. Along the altitudinal gradient (6 to 1,000 masl), an inconsistent increase in silt + clay, annual rainfall, SOC concentration, and stock was also observed. However, beyond 1,000 masl, the corresponding increase was linear. The wide variability in SOC concentration and stock, therefore, resulted from the interaction of land uses, altitudinal gradients, textural gradients and climatic variables Copyright © 2014 John Wiley & Sons, Ltd