Herbivore outbreaks in warmer forests: soil biogeochemical responses to soil warming and an ephemeral, intense outbreak of leaf-feeding insect herbivores

这项研究在橡树为主的森林中使用了土壤变暖实验设施，首次研究了昆虫爆发如何影响当前温度和未来预期的温暖土壤下树木的养分循环和可用性。 在美国东南部，毛虫的爆发对橡树造成了很高的损害率，包括高达100%的个别树木落叶。涉及这次爆发的物种，黑点棕（Cissusa spadix）和普通橡树蛾（Phoberia atomaris），以前从未听说过爆发（Cissusa）或很少爆发（Phoberia）。然而，2010年5月，美国东南部有史以来第一次爆发了锡苏萨火山，2011年5月，这两种毛虫都表现出爆发数量，并造成广泛的落叶。2012年4月，这些毛虫再次爆发，但比往年提前了一个月，可能是由于2011-2012年的暖冬。如此大量的食叶昆虫在几周内产生大量排泄物（粪便）和其他土壤养分添加物，可能会影响一整年或更长时间的养分生物地球化学动态。 这项研究将是第一个解决昆虫爆发和温暖的土壤如何影响树木的重要营养物质的可用性。昆虫爆发发生得越来越频繁，预计随着气候变暖，频率会增加。 了解森林生态系统如何应对食叶昆虫的爆发关系到森林管理者，木材采伐者，徒步旅行者，露营者以及当地和区域业主。 这项工作将有相关的了解土壤养分的树木在当前和未来的温暖条件下，因此，未来的生态系统服务对社会很重要。这些服务包括但不限于提供木材、森林碳固存、野生动物栖息地和流域完整性。在每年爆发的几个星期里，大量的粪便落下，听起来像毛毛雨，每棵树上成千上万的毛毛虫在夜间爬上树干，引起了公众的兴趣，并引起了媒体的广泛报道，为与公众对话提供了一个极好的机会。

This study uses a soil warming experimental facility in an oak-dominated forest to examine for the first time how insect outbreaks affect nutrient cycling and availability to trees under both current temperatures and warmer soils expected in the future. In the southeastern United States caterpillar outbreaks have inflicted high rates of damage to oak trees, including up to 100% defoliation of individual trees. Species involved in this outbreak, black-dotted brown (Cissusa spadix) and common oak moth (Phoberia atomaris), were never known to outbreak before (Cissusa) or only rarely (Phoberia). However, in May 2010 Cissusa broke out for the first time ever recorded in the southeastern U.S., and in May 2011 both caterpillars exhibited outbreak numbers and caused extensive defoliation. In April 2012 these caterpillars broke out again but a month earlier than previous years, likely due to the mild winter of 2011-2012. Such large numbers of leaf-eating insects in a few weeks produce large quantities of excrement (frass) and other soil nutrient additions that may impact nutrient biogeochemical dynamics over an entire year or more. This study will be the first to address how insect outbreaks and warmer soils affect the availability to trees of important nutrients.Insect outbreaks have been occurring more frequently and are projected to increase in frequency as climate warms. Understanding how forest ecosystems respond to outbreaks of foliage-eating insects concerns forest managers, timber harvesters, hikers, campers, and local and regional property owners. This work will have relevance for understanding soil nutrient availability to trees under current and future warmer conditions and, therefore, for future ecosystem services important to society. These services include, but are not limited to, provisioning of timber, forest carbon sequestration, wildlife habitat, and watershed integrity. During several weeks of outbreak each year, falling frass abundant enough to sound like drizzle and nightly climbing of thousands of caterpillars (per tree) up tree trunks garners much public interest and generates extensive media coverage, providing an excellent opportunity for discourse with the public.