The tropospheric ozone concentrations over southern Africa are relatively high due to large precursor emissions from biomass burning, vegetation and anthropogenic sources and the intensity of solar radiation. In this study, we summarize ozone concentration data from both literature and new measurements. Further, we present data on the accumulated vegetation exposure to ozone in terms of the AOT40 index, which is calculated for the sites with hourly ozone and radiation data, with an aim to assess the potential for adverse effects on vegetation. As the seasonal variation of ozone concentrations is large, we discuss the effect of growing season onset on the stomatal gas exchange and the related potential for vegetation impacts. Finally, future research needs are discussed.
The tropospheric ozone concentrations over southern Africa are relatively high due to large precursor emissions from biomass burning, vegetation and anthropogenic sources and the intensity of solar radiation. In this study, we summarize ozone concentration data from both literature and new measurements. Further, we present data on the accumulated vegetation exposure to ozone in terms of the AOT40 index, which is calculated for the sites with hourly ozone and radiation data, with an aim to assess the potential for adverse effects on vegetation. As the seasonal variation of ozone concentrations is large, we discuss the effect of growing season onset on the stomatal gas exchange and the related potential for vegetation impacts. Finally, future research needs are discussed.
Since the start of the Anglo-Boer War today 120 years ago thousands of publications, written or typed reports and other creations have been produced to narrate the war events, express opinions on its origins, causes, course, results and legacy and on participants in the struggle. This process is ongoing, since the debate amongst both professional historians and interested amateurs on exactly what happened and why is still raging and new information on the war still crops up. The history of the Anglo-Boer War is truly a neverending discourse. As the author of a number of books on the war, I have consulted hundreds of both published and unpublished sources. Some were of limited value, but a small percentage of the published books were of such high value that they formed part of a small stack of books that found a permanent home on my desktop while I was in the writing process. Pieter Cloete’s The Anglo-Boer War – A Chronology, both the original English version and the enlarged Afrikaans version published in 2010, was always part of that stack. It is to me a privilege to write a foreword for the user-friendly and meticulously researched book. It not only contains a wealth of information but a detailed source list and an extensive index. There are few, if any, more helpful reference books on the war and thus represents an essential resource to anyone with a more than superficial interest in the Anglo-Boer War. DR JACKIE GROBLER Historian and author Recently retired after 40 years at the Department of Historical and Heritage Studies, The University of Pretoria.
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