Woody cover in wet and dry African savannas after six decades of experimental fires

1. Fire is an integral process in savannas because it plays a crucial role in altering woody cover of this globally important biome. 2. In this study we examine the long term effects of varying fire frequencies over a 60 year time period in South Africa. We analyse the effects of fire exclusion and of experimental burns every 1, 2 and 3 years on woody cover, tree abundance and stem structure on a wet and dry savanna. 3. Increased fire frequency did not display a consistent effect on woody cover. The presence of fire, irrespective of frequency, was much more influential in lowering tree abundance in the wet savanna than the dry savanna. In the dry savanna, fire was more effective in greatly increasing coppicing in trees, when compared to the wet savannas. 4. Synthesis: The effects of fire on three measures of savanna woody vegetation differed between wet and dry experimental sites. We suggest that vegetation responses to fire are dependent on local conditions, which are likely influenced...1. 火是稀树草原（savanna）不可或缺的生态过程，因其在改变这一全球重要生物群系（biome）的木本植被覆盖度方面发挥着关键作用。2. 本研究针对南非一处为期60年的长期定位样地，探究不同火烧频率所产生的长期生态效应。我们分析了禁火、以及每1年、2年、3年实施一次控制性火烧的处理组，对湿润与干旱稀树草原的木本覆盖度、树木丰度以及茎部结构的影响。3. 火烧频率提升对木本覆盖度并未呈现一致的影响效应。无论火烧频率高低，火烧对湿润稀树草原树木丰度的降低效果均显著强于干旱稀树草原。相较于湿润稀树草原，干旱稀树草原中的火烧对树木萌蘖的促进效果更为显著。4. 综合结论：火烧对稀树草原木本植被三项观测指标的影响，在湿润与干旱实验样地中存在显著差异。本研究认为，植被对火烧的响应取决于局地环境条件，而该条件大概率受……