Collaborative Research: Does the legacy of long-term chronic climate change alter ecosystem responses to short-term climatic extremes?

气候变化在美国中西部可能表现为逐渐变暖和降雨量变化的结合，沿着热浪和干旱等极端天气事件的增加。这种渐进和极端的变化通常是独立研究的，但它们最有可能同时发生，这就提出了关于它们如何相互作用的重要问题。例如，生态系统对干旱的反应性质是否会受到温度逐渐升高的影响？该项目将通过建立在堪萨斯草原的长期气候变化研究，降雨操纵图（RaMPs）实验来解决这个问题。RaMPs实验已经改变了15年的降雨模式，更大的降雨事件和更长的事件间隔，以及10年的持续变暖（1-2摄氏度）。这些处理导致土壤持续干燥，植物水分胁迫增加，植物生长减少，最丰富的草种种群发生遗传变化，土壤二氧化碳排放量，营养物质和微生物发生变化。这些不同的反应预计将增加生态系统的极端干旱和干旱后恢复的能力。为了验证这些预测，两年的极端干旱（类似于20世纪30年代的沙尘暴），然后是一年的正常降雨量将被施加在实验地块上，并将测量多种生态系统的反应。本课程将提高学生对科学过程的基本理解，并通过讲座，课堂项目和实地考察向他们介绍气候-生态系统相互作用的复杂性，展示怀俄明州，科罗拉多和新墨西哥州气候变化实验的结果。

Climate change may be manifested in the Midwestern United States as a combination of gradual warming and changes in rainfall along with increases in extreme weather events such as heat waves and droughts. Such gradual and extreme changes have typically been studied independently, however they are most likely to occur simultaneously, raising important questions about how they may interact. For example, will the nature of ecosystem responses to drought be affected by a gradual increase in temperature? This project will address this question by building on a long-term climate change study in a Kansas grassland, the Rainfall Manipulation Plots (RaMPs) experiment. The RaMPs experiment has imposed 15 years of altered rainfall patterns, larger rainfall events and longer periods between events, and 10 years of continuous (1-2 degree C) warming. Those treatments have resulted in consistently dry soils, increased plant water stress, reduced plant growth, genetic changes in populations of the most abundant grass species, and changes in soil carbon dioxide emissions, nutrients, and microbes. These varied responses are predicted to increase the ecosystem's resistance to extreme drought and its ability to recover after drought. To test those predictions, two years of extreme drought (similar to the 1930's dust bowl) followed by a year of normal rainfall will be imposed on experimental plots and multiple ecosystem responses will be measured.A field-based course for undergraduates entitled 'Climate Change and Grasslands' will be offered. This course will enhance students' basic understanding of the scientific process and introduce them to the complexities of climate-ecosystem interactions through lectures, class projects and field trips that showcase results from climate change experiments in Wyoming, Colorado and New Mexico.