An often cited rule of savanna fire ecology is that early dry-season fires burn less intensely than late dry-season ones; however, few studies base their experimental design on the practices of fire managers in working landscapes. The objective of this research was to study the factors influencing fireline intensity, combustion, and patchiness for a West African savanna under common vegetation and land management practices. We conducted 97 experimental fires by selecting burn plots and seasonal timing (early, n = 33; middle, n = 44; or late, n = 20) based on local practices in a typical working landscape. We collected data for biomass consumed, grass type, scorch height, speed of fire front, visual efficiency (patchiness), fire type, and ambient air conditions. We used multiple regression analysis to determine the key factors affecting fire intensity. Mean intensity was lowest for the middle season fires and highest for the late season fires. Minimum fire intensity increased over the fire season except for a sharp drop mid season, while maximum intensity progressively decreased. Seasonal values were highly variable. Fire intensity was moderately positively correlated with scorch height and more modestly correlated with visual efficiency, but only marginally correlated with combustion completeness. Average combustion completeness increased weakly as the dry season progressed. Intensity of back-fires was determined primarily by seasonal timing and the associated ambient humidity and wind and, to a lesser extent, grass characteristics. Head-fire intensity was only feebly responsive to wind speed. We found that, at the peak time of West African savanna burning, the intensity of fires decreased. Fire behaviors in working West African landscapes were more dependent on fire type and wind than seasonality. Finally, we found that fire intensity values were lower than those reported elsewhere due to the more representative conditions of the fire setting (under lower afternoon winds) and fuel loads (lower biomass on working landscapes). Future research should focus on the ecological impacts of fires set under such conditions on growth and death rates of savanna trees.

中文翻译：

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非洲稀树草原工作景观中火灾强度的决定因素

稀树草原火灾生态学的一个经常被引用的规则是，旱季早期火灾的燃烧强度低于旱季晚期火灾的燃烧强度。但是，很少有研究将实验设计基于工作环境中消防经理的做法。这项研究的目的是研究在常规植被和土地管理实践下影响西非大草原火线强度，燃烧和斑驳的因素。我们根据典型工作环境中的当地实践，通过选择燃烧区和季节时机（早，n = 33；中，n = 44；晚，n = 20）进行了97次实验性火灾。我们收集了消耗的生物量，草类型，焦烧高度，火锋速度，视觉效率（斑驳度），火类型和周围空气条件的数据。我们使用多元回归分析来确定影响火势的关键因素。平均强度在中期火灾中最低，而在后期火灾中最高。除火季中期急剧下降外，最小火势在火季增加，而最大火力逐渐降低。季节性值变化很大。火灾强度与焦烧高度呈正相关，而与视觉效率的相关程度较小，但与燃烧的完整性仅存在少量相关性。随着干燥季节的进行，平均燃烧完成度微弱增加。逆火的强度主要由季节时机以及相关的环境湿度和风以及（在较小程度上）草的特性决定。头火强度对风速的响应很小。我们发现，在西非稀树草原燃烧的高峰时间，火势减弱。在工作中的西非景观中，火灾行为更多地取决于火种和风，而不是季节性。最后，我们发现火势强度值比其他地方报告的要低，这是因为火势环境（在较低的午风下）和燃料负荷（工作景观中的生物量较低）更具代表性。未来的研究应集中在这种情况下的大火对热带稀树草原的生长和死亡率的生态影响上。我们发现，由于烈火环境（午后风较小）和燃料负荷（工作景观中的生物量较低）更具代表性，火灾强度值低于其他地方的报告。未来的研究应集中在这种情况下的大火对热带稀树草原的生长和死亡率的生态影响上。我们发现，由于烈火环境（午后风较小）和燃料负荷（工作景观中的生物量较低）更具代表性，火灾强度值低于其他地方的报告。未来的研究应集中在这种情况下的大火对热带稀树草原的生长和死亡率的生态影响上。