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。上世纪30年代和2012年的干旱凸显了草原在严重降雨短缺面前的脆弱性。这些干旱造成了大约300亿美元的损失，并对动物栖息地、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以及它们对极端干旱的反应，人们知之甚少。这是一个重要的遗漏，因为昆虫调节草地养分循环，抑制初级生产，并且在严重干旱（例如沙尘暴）期间经常达到暴发密度。该奖项将量化昆虫对美国中西部从落基山脉到密西西比河草原的初级生产和养分循环的调节。该奖项将研究干旱对草原昆虫的影响，以及干旱如何导致有害虫害的爆发，从而进一步加剧干旱状况。此外，该奖项将培训两个研究生课程，并为来自传统上代表性不足的群体的多名本科生提供实践经验。最后，这项研究将产生一个全面的和现代的指南，以识别蚱蜢在中西部草原，将使用管理人员，研究人员和教育工作者。这个项目由两个独立的部分组成。一项野外操作研究将在三个草原上施加严重的干旱，这些草原的降水梯度为干旱至湿润。干旱处理将与昆虫封闭相结合。在三年的时间里，研究人员将测量地上的净初级产量、营养循环、植物生理学、植物性状和食草昆虫密度。将对这些数据进行分析，以确定昆虫在环境和干旱条件下调节产量和养分循环的机制。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养分循环。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.