Land-use change and Biogeochemical controls of soil CO2, N2O and CH4 fluxes in Cameroonian forest landscapes

Verchot, L.V. and Dannenmann, M. and Kengdo, S.K. and Njine-Bememba, C.B. and Rufino, M.C. and Sonwa, D.J. and Tejedor, J. (2020) Land-use change and Biogeochemical controls of soil CO2, N2O and CH4 fluxes in Cameroonian forest landscapes. Journal of Integrative Environmental Sciences, 17 (2020). pp. 45-67. ISSN 1943-815X

Abstract

Deforestation and land-use change are accelerating in the Congo Basin and elsewhere in the tropics affecting the soil-atmosphere exchange of greenhouse gases (GHG). There is a lack of data from Central Africa. We quantified CO2, CH4, and N2O fluxes at the soil-atmosphere interface in a secondary forest, a cocoa agroforest, and an unfertilized cropland in a typical central African forest transition landscape. Soil respiration was highest in the secondary forest (15.37 ± 3.42 Mg C ha−1 y−1), intermediate in the cacao agroforest (12.26 ± 2.91 Mg C ha−1 y−1) and the lowest in the unfertilized cropland (8.74 ± 2.62 Mg C ha−1 y−1). Likewise, N2O fluxes were highest in the secondary forest (2.17 ± 0.20 kg N ha−1 y−1), intermediate in the cacao agroforest (1.40 ± 0.08 kg N ha−1 y−1) and lowest in the unfertilized cropland (1.04 ± 0.15 kg N ha−1 y−1). Soils were a sink for atmospheric CH4 and sink strength was high in the secondary forest (−3.60 ± 1.83 kgC ha−1 y−1) and cacao agroforest (−3.61 ± 2.09 kgC ha−1 y−1) and low in the unfertilized cropland (−1.90 ± 1.59 kgC ha−1 y−1). Variation in soil water content rather than temperature was the dominant driver of seasonal variations of the fluxes and N availability affected both N2O and CH4 fluxes. Our results suggest that tropical land-use change decreases soil respiration, decreases the strength of the soil CH4 sink and decreases N2O emissions, in landscapes that do not practice agriculture with chemical fertilization. We quantified fluxes of CO2, CH4, and N2O at the soil-atmosphere interface in a secondary forest, a cocoa agroforest, and an unfertilized cropland in a typical central African forest transition landscape. Soil respiration was highest in the secondary forest (15.37 ± 3.42 Mg C ha−1 y−1), intermediate in the cacao agroforest (12.26 ± 2.91 Mg C ha−1 y−1) and the lowest in the unfertilized cropland (8.74 ± 2.62 Mg C ha−1 y−1). Likewise, N2O fluxes were highest in the secondary forest (2.17 ± 0.20 kg N ha−1 y−1), intermediate in the cacao agroforest (1.40 ± 0.08 kg N ha−1 y−1) and lowest in the unfertilized cropland (1.04 ± 0.15 kg N ha−1 y−1). Soils were a sink for atmospheric CH4 and sink strength was high in the secondary forest (−3.60 ± 1.83 kg CH4 ha−1 y−1) and cacao agroforest (−3.61 ± 2.09 kg CH4 ha−1 y−1) and low in the unfertilized cropland (−1.9 ± 1.59 kg CH4 ha−1 y−1). Variation in soil water content rather than temperature was the dominant driver of seasonal variations of the fluxes and N availability affected both N2O and CH4 fluxes. Our results suggest that tropical land-use change decreases soil respiration, decreases the strength of the soil CH4 sink and decreases N2O emissions, in landscapes that do not practice agriculture with chemical fertilization.