Biochemical Cycles: The land surface of Savanna is the interface for the exchange of radiation, heat, moisture, CO2, and other trace gases with the atmosphere . These important exchanges are modulated by ecosystem characteristics such as structure, species composition, and physiological function. Tropical savanna is a key terrestrial biome that dominates 15% of the global land surface and warrants special attention because of its vast extent, high productivity, rapid carbon turnover, vulnerability to climate change (which will alter fire regimes and water availability), poor management (i.e., high population pressures and overutilization for grazing and firewood), and land use change (Canadell et al. 2003). At aglobal scale, savanna distribute. Predictions:Various Savannah reserves are examined to determine whether they are likely to lose substantial numbers of large herbivores if they become isolated. The relationship between the number of ungulate species and the size of each reserve is examined and compared to predictions established from existing island bio geographic studies. In the case of the savannah reserves, no significant relationship was found. However, when the data were re-analysed for reserves of similar habitat, significant though low z-values of 0.04 and 0.08 were established. For discrete ecosystems rather than reserves a steeper z-value of 0.14 was found.
PREDICTIONS:The significance of island biogeographic theory to the design of nature reserves is limited, at least in the savannahs. Most of the variation in the number of species in areas which can be practically established as reserves can be explained by habitat and landscape diversity. Whether the savannah reserves became faunal islands will be decided by political and economic policies and practices rather than the principles of ecological design. The design of reserves in the past is considered to have been based on sound ecological principles in most cases, even though these were not recognized at the time.