Afforestation of semi-arid regions of Mongolia: carbon sequestration in trees and increase of soil organic carbon

Abstract

This work examines the variation of carbon sequestration (considered as the sum of above- and below-ground plant biomass production added to soil organic carbon) occurring in two sites (named respectively BN and ER) characterized by a semi-arid climate after planting three tree species (Populus sibirica, Ulmus pumila, and Hippophae rhamnoides). Soil organic carbon (SOC) was analyzed at four different depths (from 0–60 cm). In these two sites, the three tree species contributed differently to carbon sequestration. We found that above-ground plant biomass (leaf, branch, stem) was higher at the BN site whereas at the ER site prevailed below-ground biomass. That is probably due to the low tree density in BN site and the higher soil moisture content present in ER site. Among the three tree species considered, P. sibirica showed the highest biomass value. The SOC values were highest in the topsoil layer (0-40 cm) and decreased with depth. This works clearly shows that in semi-arid lands carbon sequestration depends on the environmental factors that characterize the site, the tree density, and the tree species selected.