Carbon Changes Following the Establishment of Exclosure on Communal Grazing Lands in the Semi-Arid Lowlands of Tigray, Ethiopia

Abstract

Most dryland ecosystems are degraded and are currently far from saturated with carbon. This indicates their potential to sequester a significant amount of carbon through sequestration measures. In this study, we: (1) investigated changes in ecosystem carbon stocks following establishment of exclosure on communal grazing lands, and (2) identified easily measurable biophysical and management-related variables which can be used to predict ecosystem carbon stocks restoration in the semi-arid lowlands of northern Ethiopia. We measured above-ground and soil carbon stocks, determined soil characteristics and collected climatic data and management information from replicated (n = 3) exclosures of 5, 10 and 15 years old which were paired with grazing lands. All exclosures displayed higher ecosystem carbon stocks than the adjacent grazing lands. Differences in ecosystem carbon stocks between exclosures and grazing lands varied between 18 (±2.8) and 40 (±6.3) Mg C ha−1 and increased with exclosure age. In exclosures and in communal grazing lands, much of the variability in ecosystem carbon stocks was explained by a combination of precipitation, silt and clay content, woody biomass, vegetation canopy cover and exclosure age. Our results help to establish baseline information for carbon sequestration projects such as the establishment of exclosures on communal grazing lands, and to predict the expected ecosystem carbon storage under exclosures.