Predicting the effects of extreme drought on insect herbivore control of grassland ecosystem function

在过去的2000年里，北美的极端干旱以惊人的频率发生。最近发生在1930年代和2012年的干旱凸显了草原易受严重降雨短缺的影响。这些干旱造成了估计300亿美元的损失，并对动物栖息地的可用性、土壤和养分循环造成了重大变化。昆虫在美国草原上的作用及其对极端干旱的反应鲜为人知。这是一个重要的疏漏，因为昆虫调节草原养分循环，抑制初级生产，并经常在严重干旱(例如沙尘暴)期间达到暴发密度。该奖项将量化美国中西部从落基山脉到密西西比河的草原上昆虫对初级生产和营养循环的调节。该奖项将讨论干旱对草原昆虫的影响，以及干旱可能如何导致有害的虫害暴发，从而进一步加剧干旱条件。此外，该奖项将培训两个研究生课程，并为来自传统代表性不足群体的多名本科生提供实践经验。最后，这项研究将产生一份全面的、现代的中西部草原蝗虫鉴定指南，将对管理者、研究人员和教育工作者有用。该项目由两个独立的部分组成。一项操纵性的实地研究将在三个草原上造成严重干旱，横跨干旱到中等降水梯度。干旱处理将与昆虫灭绝相结合。在三年的时间里，研究人员将测量地上净初级生产力、营养循环、植物生理学、植物特征和昆虫食草动物密度。这些数据将被分析，以确定昆虫在环境和干旱条件下调节生产和养分循环的机制。一项实验室实验将确定植物和昆虫在干旱条件下的生理变化。生理测量将被纳入数学模型，以预测美国中部草原在环境和干旱条件下的营养循环。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Extreme droughts in North America have occurred with surprising frequency for the last 2,000 years. Recent droughts of the 1930s and 2012 highlighted the vulnerability of grasslands to severe rainfall shortages. These droughts resulted in an estimated $30 billion in damages and caused significant changes to animal habitat availability, soils, and nutrient cycling. The role of insects in US grasslands and their responses to extreme drought is poorly understood. This is an important omission, because insects regulate grassland nutrient cycling, suppress primary production, and often achieve outbreak densities during severe droughts (e.g. the Dust Bowl). This award will quantify insect regulation of primary production and nutrient cycling in US grasslands spanning the Midwest, from the Rocky Mountains to the Mississippi River. The award will address drought impacts on grassland insects and how drought may cause harmful pest outbreaks that could further exacerbate drought conditions. In addition, this award will train two graduate studies and provide hands-on experience for multiple undergraduate students from traditionally underrepresented groups. Finally, this research will produce a comprehensive and modern guide to grasshopper identification in Midwestern grasslands that will be of use to managers, researchers, and educators.This project consists of two separate components. A manipulative field study will impose severe drought at three grasslands across a xeric to mesic precipitation gradient. Drought treatments will be combined with insect exclosures. Over three years, researchers will measure aboveground net primary production, nutrient cycling, plant physiology, plant traits, and insect herbivore densities. These data will be analyzed to identify the mechanism by which insects regulate production and nutrient cycling under ambient and drought conditions. A laboratory experiment will identify how both plant and insect physiology change under drought conditions. Physiological measurements will be incorporated into mathematical models to predict nutrient cycling under ambient and drought conditions in grasslands of the central US.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.