Influence of selected land use and land cover types on greenhouse gas fluxes in drylands of Eastern Kenya

Abstract

Efforts have been made in the recent past to improve knowledge of soil greenhouse gas (GHG) fluxes in Sub-Saharan Africa. However, information on land use and land cover (LULC) types’ influence on soil GHG fluxes in Kenyan drylands is still limited. This study aimed to quantify soil GHG (carbon dioxide-CO2, nitrous oxide-N2O and methane-CH4) fluxes in forested land, grassland, shrubland and cropland in Kibwezi West, during dry (< 0.05 m3m-3 soil moisture) and wet (> 0.16 m3m-3 soil moisture) periods. A completely randomized design (CRD) was used, treatments being the different LULC types, each having three sampling points with five replicates. GHG measurements were done for six weeks (thrice weekly) using static chambers and gas chromatography. Soil organic carbon (SOC), total nitrogen (TN), soil moisture (SM) and soil temperature (ST) were also measured. SOC and TN concentrations decreased with depth and were significantly (p value < 0.05) different across the LULC types and moisture periods. The concentrations were higher in forested land and least in cropland. The overall mean of CO2, CH4 and N2O fluxes varied significantly (p value < 0.05) across the LULC types and moisture periods, and ranged from 38.59 to 123.23 mg CO2-C m-2 h-1, -0.0125 to 0.0045 mg CH4-C m-2 h-1 and 3.112 to 19.783 μg N2O-N m-2 h-1 respectively. Further, GHG fluxes were higher during the wet period than during the dry period. Overall means of CO2 and N2O fluxes followed the order; forested land > grassland > shrubland > cropland. CH4 had negative fluxes in all LULC types except in shrubland. SOC and TN concentrations positively correlated with CO2 and N2O fluxes in both periods. SM was related positively to CO2 and CH4, and negatively to N2O in all LULC types except in cropland. ST was related positively to CH4 and N2O, and negatively to CO2 in all LULC types except forested land. Despite being GHG sources, forested land, grassland and shrubland stored significant amounts of SOC and TN concentrations. Protecting and restoring these LULC types could mitigate climate change by sequestering GHG emissions, necessitating the implementation of sustainable land management policies and legislation.