Quantity and Quality of C, N and P in Oxisols Under Different Vegetations in Forest-Savanna Transitional Area At Eastern Cameroon.

Forest-Savanna transitional area is widely distributed in the central Africa and deforestation has been occurred seriously, due to various human activities. To conserve the biodiversity by proper land management in this area, it is necessary to understand the characteristics of soil nutrients (C, N and P) with its physicochemical property. In the present study, we conducted the field survey around the Eastern Cameroon and make 10 soil profiles (80 cm depth) from five forest and five savanna profiles. Soil samples were collected from each layer and analyzed for pH(H₂O), pH(KCl), soil texture, bulk density, exchangeable and total bases (K, Na, Ca, Mg), CEC, oxalate extractable Al and Fe, DCB extractable Al and Fe, total C, N and P contents, and Hedley fractionated P. All soils were classified as Oxisols. The most soil physicochemical properties were not different between the vegetations, while the clay content is clearly larger in forest than that in savanna, and bulk density was clearly smaller in forest than that in savanna at surface layers (0-5 and 5-10 cm; p<0.05). Accumulated C, N and P at the soil profile (0-80 cm) was 87.9, 7.7 and 3.7 t C N P ha^-1 in forest, respectively, and was 98.6, 7.1 and 3.7 t C N P ha^-1 in savanna, respectively, and there is no clear difference for the vegetation. On the other hand, quality of soil organic matter, i.e., C/N ratio, was clearly higher in savanna (13.0~15.7) than in forest (11.0~12.0) in the upper layer (0-40 cm; p<0.05). In addition, the rate of NaOH-extractable inorganic P, fixed by Al and Fe oxide, to the total P was also clearly higher in savanna (13.1~15.3%) than in forest (9.6~10.4%) for same soil depth (0-40 cm; p<0.05). These results indicate that accumulated C, N and P quality of upper layer should be different between the forest and savanna, indicating the different pattern of nutrient mineralization and hence degradation after cultivation.