BIOGENIC HYDROCARBON EMISSIONS FROM SOUTHERN AFRICAN SAVANNAS

Biogenic nonmethane hydrocarbon (NMHC) emissions were investigated at two field sites in the Republic of South Africa that include five impo rtant southern African savanna landscapes. Tropical savannas are a glo bally important biome with a high potential for biogenic emissions but no NMHC emission measurements in these regions or in any part of Afri ca have been reported. Landscape average hydrocarbon emissions were es timated by characterizing plant species composition and foliar density at each site, identifying and characterizing NMHC emissions of the mo st abundant plant species, and identifying and characterizing NMHC emi ssions of plant species with the highest NMHC emission rates. A hand-h eld portable analyzer proved to be a useful tool for identifying plant s with high emission rates. A branch enclosure system, with gas chroma tography and flame ionization detector, was used to quantify isoprene and monoterpene emission rates. Emission rates were species-specific a nd several genera had both high and low emitters. At least some specie s with high emission rates were identified in most savanna types. High and low emitters were found on both nutrient-rich and nutrient-poor s oils. Landscape average emission capacities for the five savanna types range from 0.6 to 9 mg C m(-2) h(-1) for isoprene and about 0.05 to 3 mg C m(-2) h(-1) for monoterpenes. The savanna emission rates predict ed by existing global models are within the range estimated for these five savanna types.