Soil Carbon Sequestration Under Rubber Plantations in North-East India

Abstract

Rubber plantations on degraded forest lands are expanding worldwide due to economic, social and environmental perspectives. The study was conducted to evaluate the temporal effects of rubber plantations on soil carbon (C) sequestration in the north-eastern Indian state of Tripura. Composite soil samples were randomly collected at 0-15 (surface) and 15-30 cm (sub-surface) depths from 0 (control), 5,10, and 20 years old rubber plantations, 2-mm sieved, air-dried, and analyzed for oxidizable (COx), non-oxidizable (CNOx), and total C (CT) concentration, bulk density (rho b), and selected properties. Results showed that soil C concentration, stock and sequestration varied significantly by rubber plantations' age. Averaged across soil depth, the COx concentration was increased by 32-105% with increasing rubber plantations' age. Likewise, the CT concentration increased by 14-62% over time. The increase in COx and CT concentration was more pronounced at surface soil. The proportion of COx in CT was increased (13%) with an associated decrease in CNOx content. Averaged across soil depth, the COx, CNOx, and CT stocks increased quadratically over time. Soil profile-wise CT stock was increased by 14-57% which accounted for an accumulation of 34 Mg C ha(-1) over a 20 year period. The CT sequestration increased quadratically, which accounted for 956, 919 and 852 kg C ha(-1) year(-1) under 5, 10 and 20 years old rubber plantations, respectively. Results suggest that, if managed properly, rubber plantation on degraded tropical forest lands can be a C sink over time.