Sequestration potential of soil organic carbon under selected land use, land cover and climate change scenarios in Kibwezi West dryland, Eastern Kenya

Abstract

Information on the spatialtemporal distribution and trends in SOC stocks is limited, especially in drylands of Kenya. Understanding the spatial and temporal changes in SOC stocks in relation to Land use and land cover (LULC), and climate change is essential in advising on sustainable land use management (SLM) practices. This study assessed the spatial and temporal changes in SOC stocks from four LULC types (cropland, forested land, grassland and shrubland) in Kibwezi West, Kenya. A completely randomized design (CRD) was used, with the different LULC types as treatments, each having three sampling points with five replicates. Baseline SOC stocks were analyzed from soil samples collected from the topsoil (0–30 cm) of the four LULC types. Rothamsted carbon model (RothC) was used in simulating SOC under three land management scenarios (BAU – business-as-usual scenario/current land use, LSLM – low SLM (5% increase in carbon inputs) and HSLM – high SLM (20% increase in carbon inputs)) and two climate change scenarios (Representative Concentration Pathways (RCP) 4.5 and 8.5). The SOC stocks significantly (p < 0.05) varied across the LULC types, recording Mg C ha−1 of 20.21 in cropland, 62.13 in forested land, 53.80 in grassland and 30.80 in shrubland. Projections under different land management scenarios showed a higher SOC sequestration potential (Mg C ha−1 yr−1) under HSLM (0.71–1.63) than in LSLM (0.16–1.24) and BAU (0.13–1.12). A reduction in SOC sequestration potential was strongly (p < 0.05) influenced by warmer climate (RCP 8.5) and absence of SLM. The study has shown that HSLM practices, once adopted, could be a measure towards enhancing SOC sequestration and hence climate change mitigation. This study contributes to the body of knowledge on spatial and temporal distribution of SOC in drylands of Kenya. The results will be instrumental in guiding SLM practices and policies in Kibwezi West and other similar landscapes.