Spatial and temporal variations in biogenic volatile organic compound emissions for Africa south of the equator

L Otter,C Wiedinmyer,A Guenther,P Harley,G Fleming,J Greenberg

doi:10.1029/2002jd002609

Abstract

Improved vegetation distribution and emission data for Africa south of the equator were developed for the Southern African Regional Science Initiative (SAFARI 2000) and were combined with biogenic volatile organic compound (BVOC) emission measurements to estimate BVOC emissions for the southern African region. The BVOCs are estimated to total 80 Tg C yr−1 for the region, with isoprene and monoterpenes contributing 56 and 7 Tg C yr−1, respectively. The large uncertainties, particularly in terms of basal emission capacity assignment, associated with these outputs are discussed. Woodlands are predicted to be the dominant vegetation type, covering 23% of southern Africa, and are the largest annual source of isoprene (20 Tg C), monoterpenes (3 Tg C), and other VOCs (4 Tg C). Mopane savannas and woodlands are predicted to contribute over 75% of all monoterpenes, primarily from light‐dependent emission processes. Rain forests cover only 3.5% of the total area but have high annual emission rates (9.8 g C m−2 yr−1). In the tropical regions with high rainfall, warm temperatures, and high plant productivity throughout the year, the seasonal variation in VOC emissions was small. In subtropical regions, dominated by highly seasonal savannas and grasslands, large variations were predicted, with emissions declining by up to 85% during dry winter periods (June–August) due to low leaf area index after leaf drop.

Highlights

[2] Volatile organic compounds (VOCs) consist of a wide variety of chemical species that can be emitted into the atmosphere, where they react with other compounds
This paper presents a detailed land cover data set for southern Africa, which has been developed for the specific purpose of modeling biogenic emissions
The results presented here enable an evaluation of the seasonal and spatial variability in the Biogenic volatile organic compound (BVOC) emissions throughout southern Africa

Summary

Introduction

[2] Volatile organic compounds (VOCs) consist of a wide variety of chemical species that can be emitted into the atmosphere, where they react with other compounds. Biogenic volatile organic compound (BVOC) emissions are extremely important, with vegetation producing more than 90% of the total global VOC budget (1150 TgC yrÀ1) [Guenther et al, 1995]. During the Southern African Regional Science Initiative (SAFARI 2000) [Otter et al, 2002a; Swap et al, 2002a, 2002b] further emission data were collected from Mopane woodlands and vegetative species representative of the Kalahari and Miombo woodlands [Greenberg et al, 2002; Otter et al, 2002a] Some of these data were available prior to the SAFARI 2000 study, they have not been used to estimate biogenic emissions from all of southern Africa. Understanding emissions at a landscape scale enables better predictions of future BVOC emissions as the land use in the region changes

Methods

Results

Conclusion