Micrometeorological and leaf-level measurements of isoprene emissions from a southern African savanna

through the morning hours, with midday fluxes averaging 0.34 mg m � 2 h � 1 and a maximum measured flux of approximately 1.0 mg m � 2 h � 1 . Consistent with these low fluxes, leaf enclosure measurements of woody species within the tower footprint determined that only one isoprene-emitting species, Acacia nigrescens, was present in significant numbers, comprising less than 10% of the woody biomass. Combining enclosure data with species composition and leaf area index data from the site, we estimated that the isoprene emission capacity of the vegetation within the vicinity of the tower was very low, approximately 0.47 mg m � 2 h � 1 , and patchy. Under these circumstances, low and variable fluxes are expected. Additional leaf enclosure measurements, for a total of 121 species, were made at other locations, and approximately 35% of the species was found to emit significant amounts of isoprene. Important isoprene emitting plant families included Caesalpinaceae, Mimosaceae, Papilionaceae, Euphorbiaceae, Moraceae, and Myrtaceae. Twelve members of the important savanna genus Acacia were measured, of which five species, all belonging in Subgenus Aculeiferum, Section Aculeiferum, were found to emit significant amounts of isoprene. In contrast, the plant family, Combretaceae, dominant in many savanna ecosystems, was found to contain no species which emit isoprene. INDEX TERMS: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 1615 Global Change: Biogeochemical processes (4805) Citation: Harley, P., L. Otter, A. Guenther, and J. Greenberg, Micrometeorological and leaf-level measurements of isoprene emissions from a southern African savanna, J. Geophys. Res., 108(D13), 8468, doi:10.1029/2002JD002592, 2003.