Effects of environmental factors and soil properties on soil organic carbon stock in a natural dry tropical area of Cameroon

Abstract. Researches carried out on soil organic carbon stock (SOCS) in the Sudano-Sahelian part of Cameroon are very rare. The few existing ones are mostly available in reports and concern in most cases carbon stocks in plant biomass. In order to contribute to the documentation on soils in this part of the country, the present work was designed to evaluate the SOCS in the main soil types and the influence of environmental factors and soil properties on these stocks under the natural dry tropical area of the Sudano-Sahelian zone of Cameroon. The study was undertaken in four sites, including three natural forest reserves (Laf, Zamai, Kosohon) and one national park (Mozogo), located at different latitudes. Two replications were thereafter made, thus, giving rise to three sampling points chosen per site, from 0 to 75 cm depth, for the determination of the SOCS. At each sampling point, soils were sampled using depth increments of 25 cm from the surface. The studied area is covered by Haplic Vertisols, Dystric Arenosols, Dystric Leptosols and Dystric Planosols. T-SOCS content, which refers to a depth of 75 cm, decreases with increasing latitude, with 249±26.26 Mg.ha-1 in Vertisols at Laf forest reserve in the low latitude, 199±8.00 Mg.ha-1 in Arenosols at Zamai forest reserve, 166±16.63 Mg.ha-1 in Leptosols at Kosohon forest reserve and 161±8.88 Mg.ha-1 in Planosols at Mozogo national park in the high latitude, regardless of the altitude. No significant correlation was noted between T-SOCS and the altitude. A good correlation was noted between precipitation which decreases with increasing latitude and T-SOCS, indicating the importance of climate in the distribution of T-SOCS in the study area, which directly influence the productivity of the vegetation. More than 60% of the SOCS was stored below the first 25 cm from the soil surface, a peculiarity of SOCS in the drylands. The SOCS in the Sudano-Sahelian area of Cameroon is mainly influenced by climate and vegetation.