Stocks of Nitrogen in Vegetation and Soil in West African Moist Savannas and Potential Effects of Climate Change and Land Use on these Stocks
Moist savannas which include undifferentiated moist woodlands and savannas with abundant Isoberlinia doka and I. tomentosa (also known as Sundanian woodlands and Guinea-Congolian secondary grassland and wooded grassland) extend across West Africa up to the Central African Republic. Nitrogen stocks in the standing woody vegetation, litter and soil as well as the amounts of nitrogen transferred between these stocks and that lost through savanna burning of woodland and open moist savanna types are presented. Most of the total nitrogen is in the soil and then in the woody vegetation, with the least amount in the herbaceous vegetation. In a global change scenario characterized by elevated carbon dioxide levels and increased temperatures, it is predicted that there may be a reduced grass abundance and an increased woody species cover. However, human induced land use changes usually drastically reduce woody plant numbers. It is therefore predicted that forbs and low shrubs may dominate the future vegetation of moist savannas. The implications of such vegetation changes on nitrogen stocks are discussed.