Carbon Cycles and Vegetation Dynamics of Savannas Based on Global Satellite Products
Savannas have been broadly defined as grassland-dominated ecosystems with sparse (<25%) tree cover (Eiten, 1986). Savannas in the tropical zones have been described as any ecosystem containing significant open grass cover (Grace et al., 2006). In seasonally warm biomes, savannas are undergoing rapid conversion by humans to other land uses; and while this process of savanna conversion has been less recognized than deforestation in the humid tropics, it could have just as great an impact on terrestrial carbon cycling as any other land cover change worldwide. Regional conversions rates of savannas may exceed 1% per year (San Jose and Montes, 2003), approximately twice as fast as that of rainforest conversion rates. On a global scale, this loss (often by burning and land use change) of native savanna cover in favor of agricultural uses is likely to constitute a significant flux of greenhouse gases (GHGs), mainly as carbon dioxide (CO2), to the atmosphere (Seiler and Crutzen, 1980; Andreae et al., 1998).