Land use and land cover change influence on soil organic carbon content for a pastoral area: use of geographical information system

Abstract

Data on land use and cover change and soil organic carbon (SOC) in rangelands are essential. This is because rangelands ecosystems are fragile, and poor land-use practices can significantly threaten their sustainability by depleting SOC and increasing atmospheric carbon dioxide.  This study investigated soil organic carbon variations as influenced by land use/land cover changes in the unprotected area of the Sanga agropastoral ecosystem, southwestern Uganda.  Landsat images provided data for land use and cover for 1987 and 2020. Soil organic carbon contents were investigated in farmland (FL), grassland (GL), woodland (WL), and bare land (BL) as control at 0-15 cm and 15-30 cm depths. Soil samples were analyzed for organic carbon and bulk density using the colorimetric and core ring methods, respectively.  Total soil organic carbon content was significantly high in grassland (31.55 Mg C ha-1), p=0.005, and woodland (27.89 Mg C ha-1), p=0.028 compared to bare land (16.17 Mg C ha-1). Additionally, total soil organic carbon concentration in grassland (2.10%) was higher than SOC concentration in farmland (1.39%) p=0.001 and bare land (1.00%), p<0.001, respectively. Similarly, woodlands soil organic carbon concentration (1.98%) was higher than soil organic concentrations in bare lands, p=0.003 and farmlands, p=0.028. Bulk density was significantly different at lower horizons, with farmland having a higher bulk density than other land use types, p=0.013.  Roots and litter inputs in woodlands and grasslands contributed to higher organic carbon than farmland and eroded/bare lands. Cultivation also increased the soil bulk density. This study concludes that land use and the land cover change affected soil organic carbon sequestration and bulk density. Therefore, farmers need to increase farm management practices to avoid an increase in bulk density. Further study to compare the effects of grazing intensity on SOC and modeling future SOC content in the study area is recommended.