Woody plant expansion is one of the greatest contemporary threats to fire-dependent ecosystems. Reducing woody plant prevalence is often a primary objective of prescribed burns, yet little attention has been given to understanding the efficacy of burning to reduce their abundance. Fire intensity characteristics and plant phenology/physiology, which are sometimes presented as competing hypotheses, influence how woody plants respond to a fire event. Little work has been done in the prairie-forest region of the upper Midwest to understand how fire characteristics interact with woody species phenology and/or physiology. Using a controlled field experiment, we examined effects of timing (seasonality) and intensity (temperature and duration) of fires on top-kill and resprouting of three invasive woody plants in this region (common buckthorn, Rhamnus cathartica; bush honeysuckles, Lonicera spp.; and a native species, northern pin oak Quercus ellipsoidalis). Honeysuckles and pin oak burned in the spring dormant period, a common practice in the region, resulted in low levels of top-kill and high levels of resprouting. Burning during the late growing season yielded highest levels of top-kill and lowest levels of resprouting for honeysuckles and pin oaks. However, there was no apparent effect of season or fire intensity treatment for buckthorn stems. Under all treatment combinations, buckthorn was easily top-killed but resprouted prolifically. Collectively, most prescribed burning in the Midwest appears to be conducted during the least effective season (early growing season), when top-kill is reduced and/or resprouting most pronounced. Our results indicate that fire use could be better prescribed in this region for controlling woody plants.

中文翻译：

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火灾季节性和强度对草原森林群落木本植物重新萌发的影响

木本植物的扩张是当代对依赖火的生态系统的最大威胁之一。减少木本植物的流行通常是规定燃烧的主要目标，但很少有人关注了解燃烧以减少其丰度的功效。火灾强度特征和植物物候学/生理学有时作为相互竞争的假设出现，影响木本植物对火灾事件的反应。在中西部上游的草原森林地区，了解火特性如何与木本物种物候学和/或生理学相互作用的工作很少。使用受控的田间试验，我们检查了火灾的时间（季节性）和强度（温度和持续时间）对该地区三种入侵木本植物（普通沙棘、鼠李; 灌木金银花，忍冬属植物；和一个本地物种，北针栎Quercus ellipsoidalis）。金银花和针栎在春季休眠期燃烧，这是该地区的一种常见做法，导致低水平的顶杀和高水平的再发芽。在生长后期的燃烧产生了最高水平的金银花和针叶橡树的最高水平和最低水平的再发芽。然而，季节或火强度处理对沙棘茎没有明显的影响。在所有处理组合下，沙棘很容易被杀死，但又大量繁殖。总的来说，中西部的大多数规定的燃烧似乎是在效率最低的季节（早期生长季节）进行的，此时顶杀减少和/或重新发芽最明显。我们的结果表明，在该地区可以更好地规定使用火来控制木本植物。