Influence of grazing practices and land cover types on CH 4 , CO 2 and N 2 O fluxes in semi- arid rangelands of Laikipia County, Kenya

Greenhouse gas (GHG) emissions from soils, influenced by grazing management practices and land cover types, are critical in understanding the dynamics of semi-arid rangeland ecosystems. This study was conducted in the Ilmotiok community ranch, Laikipia County, Kenya, to investigate the effects of grazing management practices (continuous and controlled grazing) and land cover types (bare ground, grass patches, and tree mosaics) on soil emissions of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). A completely randomized block design was used, with 36 sampling points established across three topographical positions under both grazing systems. Gas samples were collected for five weeks using static chambers, and GHG fluxes were analyzed using a gas chromatograph (GC). Results showed that controlled grazing significantly improved soil quality, with higher total organic carbon (TOC), total nitrogen (TN), and water-filled pore space (WFPS) compared to continuous grazing. Tree mosaics exhibited the highest TOC and TN levels, followed by grass patches, while bare ground had the lowest. Controlled grazing emitted higher CO₂-C flux (83.2 mg. m⁻².h⁻¹) than continuous grazing (21.5 mg. m⁻².h⁻¹), with tree mosaics showing the highest flux among land cover types. Nitrous oxide emissions were also higher under controlled grazing (19.4 µg. m⁻².h⁻¹) than continuous grazing (3.4 µg. m⁻².h⁻¹), with grass patches exhibiting the highest N₂O flux among land cover types. Methane fluxes varied, with continuous grazing acting as a methane sink (-0.037 mg. m⁻².h⁻¹) and controlled grazing as a slight source (0.016 mg. m⁻².h⁻¹). Grass patches showed the strongest methane sink potential (-0.034 mg. m⁻².h⁻¹). Regression analysis revealed that WFPS and TOC were strong positive drivers of CO₂ flux, while TN, soil texture, and C:N ratio showed negative relationships. Methane and nitrous oxide fluxes were positively associated with CO₂ emissions, indicating interconnected soil GHG dynamics. These findings highlight the critical role of sustainable grazing practices and diverse land cover in improving soil quality and managing GHG emissions in semi-arid rangelands. Integrating controlled grazing and vegetation restoration can enhance soil fertility, mitigate GHG emissions, and promote ecosystem resilience.