Aim An emerging framework for tropical ecosystems states that fire activity is either “fuel build‐up limited ” or “fuel moisture limited ”, that is, as you move up along rainfall gradients, the major control on fire occurrence switches from being the amount of fuel, to the moisture content of the fuel. Here we used remotely sensed datasets to assess whether interannual variability of burned area is better explained by annual rainfall totals driving fuel build‐up, or by dry season rainfall driving fuel moisture. Location Pantropical savannas and grasslands. Time period 2002–2016. Methods We explored the response of annual burned area to interannual variability in rainfall. We compared several linear models to understand how fuel moisture and fuel build‐up effect (accumulated rainfall during 6 and 24 months prior to the end of the burning season, respectively) determine the interannual variability of burned area and explore if tree cover, dry season duration and human activity modified these relationships. Results Fuel and moisture controls on fire occurrence in tropical savannas varied across continents. Only 24% of South American savannas were fuel build‐up limited against 61% of Australian savannas and 47% of African savannas. On average, South America switched from fuel limited to moisture limited at 500 mm/year, Africa at 800 mm/year and Australia at 1,000 mm/year of mean annual rainfall. Main conclusions In 42% of tropical savannas (accounting for 41% of current area burned) increased drought and higher temperatures will not increase fire, but there are savannas, particularly in South America, that are likely to become more flammable with increasing temperatures. These findings highlight that we cannot transfer knowledge of fire responses to global change across ecosystems/regions—local solutions to local fire management issues are required, and different tropical savanna regions may show contrasting responses to the same drivers of global change.

中文翻译：

---

各大洲热带稀树草原和草原对水分和燃料负荷的火灾响应阈值不同

目标 一个新兴的热带生态系统框架指出，火灾活动要么是“燃料积聚受限”，要么是“燃料水分受限”，也就是说，当你沿着降雨梯度向上移动时，对火灾发生的主要控制从燃料，燃料的水分含量。在这里，我们使用遥感数据集来评估燃烧面积的年际变化是否可以通过年降雨总量驱动燃料积累或旱季降雨驱动燃料水分来更好地解释。位置 泛热带稀树草原和草原。时间段 2002-2016。方法 我们探讨了年燃烧面积对降雨年际变化的响应。我们比较了几个线性模型，以了解燃料水分和燃料堆积的影响（燃烧季节结束前 6 个月和 24 个月的累积降雨量，分别）确定燃烧面积的年际变化，并探索树木覆盖、旱季持续时间和人类活动是否改变了这些关系。结果热带稀树草原火灾发生的燃料和水分控制在各大洲各不相同。只有 24% 的南美稀树草原燃料积聚受到限制，而 61% 的澳大利亚稀树草原和 47% 的非洲稀树草原。平均而言，南美洲从燃料限制转为湿度限制为 500 毫米/年，非洲为 800 毫米/年，澳大利亚为 1,000 毫米/年的年平均降雨量。主要结论 在 42% 的热带稀树草原（占当前燃烧面积的 41%）中，干旱加剧和更高的温度不会增加火灾，但有些热带稀树草原，尤其是在南美洲，可能会随着温度升高而变得更加易燃。