Fire plays an important role in the ecology of tropical grasslands globally. However, detailed studies comparing the response of plant functional groups to fire seasonality, and thus phenological timing, are scarce from humid Afrotropical grasslands. Such information, however, is crucial for understanding what keeps the grasslands open and for enabling evidence-based management, and conservation. We initiated an experiment in frost- and fire-prone Angolan geoxyle grasslands in 2017, investigating the effect of different timing of fires on cover and diversity of trees, grasses, geoxyles and herbs. We installed permanent, randomised plots with fire exclusion, annual early and late dry-season burning, representing the local burning practices. Functional plant groups reacted differently to the treatments, becoming apparent at species level and their performance metrics. After three years, grass species benefitted from late and no burning, and herbs from late burning, whereas geoxyles thrived under early burning. Tree growth was suppressed under late burning, and did not increase with fire exclusion. Species richness and diversity was higher in burnt than in unburnt plots. Seasonal timing of fire tips the scales between geoxyles and grasses. The extraordinary plant diversity of Angolan geoxyle grasslands is a result of pyrodiversity and frost, keeping the grasslands open even in absence of fire.

火在全球热带草原生态中发挥着重要作用。然而，比较植物功能组对火灾季节性的响应以及物候时间的详细研究，在潮湿的非洲热带草原上很少见。然而，这些信息对于了解是什么让草原保持开放以及实现基于证据的管理和保护至关重要。我们于 2017 年在易发生霜冻和火灾的安哥拉地榆草原开展了一项实验，研究了不同火灾时间对树木、草、岩土和草​​本植物的覆盖和多样性的影响。我们安装了永久性的、随机的地块，具有防火功能，每年早晚干季燃烧，代表当地的燃烧实践。功能性植物群对处理的反应不同，在物种水平及其性能指标上变得明显。三年后，草种受益于晚燃和不燃烧，草药受益于晚燃，而土木香则在早期燃烧中茁壮成长。后期燃烧抑制了树木的生长，并没有随着火焰排除而增加。焚烧样地的物种丰富度和多样性高于未焚烧样地。火灾的季节性时间提示了土工草和草之间的比例。安哥拉geoxyle草原非凡的植物多样性是高温多样性和霜冻的结果，即使没有火灾，草原也能保持开放。焚烧样地的物种丰富度和多样性高于未焚烧样地。火灾的季节性时间提示了土工草和草之间的比例。安哥拉geoxyle草原非凡的植物多样性是高温多样性和霜冻的结果，即使没有火灾，草原也能保持开放。焚烧样地的物种丰富度和多样性高于未焚烧样地。火灾的季节性时间提示了土工草和草之间的比例。安哥拉geoxyle草原非凡的植物多样性是高温多样性和霜冻的结果，即使没有火灾，草原也能保持开放。