Earthworm functional group assemblages vary with land cover/use in human-impacted landscapes of Sudano-Guinean area, Cameroon

The semiarid zones of Cameroon are experiencing rapid land degradation and desertification due to climate change and human activities. Earthworms play a crucial role in soil functioning and are important indicators of soil quality. Their role as soil process regulators and soil ecosystem engineers has been widely demonstrated. Despite their influence in maintaining ecosystem functioning in tropical soils and considering the number of ecosystems present in Cameroon, few data are available on their distribution in Cameroonian soils in general and those of the northern part (semiarid zones) particularly. This study aims to assess the abundance and biomass of earthworm functional groups in different land uses (woody savannah, grass savannah, gallery forest, and open land) impacted by human activities in the Sudano-Guinean area of Cameroon. During two rainy seasons in 2015 and 2016, we compared earthworm functional group densities and biomasses between three herbaceous land cover (HLC) classes and identified soil parameters and land use history that affect their occurrence. Results showed that earthworm functional group densities differed between land use types and herbaceous land cover. In woody savannahs, HLC over 75 % and 90 % greatly promoted the occurrence of endogeic and anecic earthworms, while in grass savannahs the densities of the two functional groups were higher in HLC over 75 %. Moreover, species from the epigeic group occurred abundantly in the gallery forests and represented about 70 % of earthworm species recorded in our study. Some environmental factors such as soil texture, pH, altitude and soil organic matter affected earthworm abundance, while previous human activities such as pasture/grazing and fallow on land uses contributed to the occurrence of at least one of the earthworm functional groups. The study highlights the importance of understanding earthworm community dynamics in the area for effective land use management and soil restoration practices in the face of land degradation and climate change.