RAPID: Responses of herbaceous annual plants to material deposition from the urban atmosphere under contrasting conditions of antecedent drought and winter rainfall

沙漠是出了名的多变环境，有些年份（相对）雨量充沛，有些年份则非常干燥。这种高变异性直接影响到一年生草本植物的生长和丰度，这些植物每年都是由前几年沉积的种子生长而来。除了提供美丽的沙漠景观，一年生草本植物也是沙漠土壤中养分循环和有机物质积累的重要贡献者。研究人员一直在调查亚利桑那州凤凰城市区汽车排放的氮氧化物等空气污染物是如何影响索诺兰沙漠的长寿灌木的，但由于在经历了十年的干旱之后，2008年和2009年出现了两年高于平均水平的冬季降水，因此研究人员获得了一个难得的机会来探索污染物对沙漠一年生植物的影响。因此，将首次研究高降雨和城市污染对一年生草本植物丰度、种类和化学组成的综合影响，这将有助于推进多因素如何单独或联合影响植物生长的理论和认识。了解城市地区的人类活动（主要与交通有关）对城市环境内部和顺风方向的沙漠过程的影响。本科生将通过接触他们所居住的栖息地的生态研究获得宝贵的经验。

Deserts are notoriously variable environments, with some years of (relatively) abundant rainfall and others of very dry conditions. The growth and abundance of annual herbaceous plants, which grow each year from seeds deposited in previous years, are directly affected by this high variability. Besides providing beautiful desert landscapes, annual herbaceous plants also are important contributors to the cycling of nutrients and build-up of organic material in desert soils. Researchers have been investigating how air pollutants such as nitrogen oxides produced by automobiles in metro Phoenix, Arizona affect long-lived shrubs of the Sonoran Desert, but were presented with a rare opportunity to explore pollutant effects on desert annual plants because two years of above-average winter precipitation occurred in 2008 and 2009, following a decade of drought. Thus, for the first time, the combined effects of high rainfall and urban pollution on the abundance, kinds, and chemical makeup of annual herbaceous plants will be studied, and this will help advance theory and understanding of how multiple factors affect plant growth singly and in combination. Developing an understanding of the impact of human activities (largely transportation-related) in urban areas on desert processes both within and downwind from the urban environment. Undergraduate students will gain invaluable experience through their exposure to ecological research in the habitat in which they live.