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

在过去的2,000年里，北美的极端干旱以惊人的频率发生。20世纪30年代和2012年的干旱凸显了草原对严重降雨短缺的脆弱性。这些干旱造成了约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。昆虫在美国草原中的作用及其对极端干旱的反应知之甚少。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，并经常在严重干旱（如沙尘暴）期间达到爆发密度。该奖项将量化从落基山脉到密西西比河的中西部美国草原的初级生产和营养循环的昆虫调节。该奖项将解决干旱对草原昆虫的影响，以及干旱如何可能导致有害害虫爆发，从而进一步加剧干旱状况。此外，该奖项还将培训两名研究生，并为来自传统上代表性不足群体的多名本科生提供实践经验。最后，这项研究将产生一个全面的和现代的指南蝗虫识别在中西部草原，将使用的管理人员，研究人员和教育工作者。一项人工实地研究将在三个草原上施加严重的干旱，从干旱到中干旱的降水梯度。干旱处理将与昆虫隔离相结合。在三年多的时间里，研究人员将测量地上净初级生产力、营养循环、植物生理学、植物性状和食草昆虫密度。这些数据将进行分析，以确定昆虫调节生产和营养循环在环境和干旱条件下的机制。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，以预测在美国中部草原环境和干旱条件下的养分循环。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

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.