RAPID: Sources and ecosystem significance of dust inputs during extremely wet and dry years in the Sierra Nevada, California

研究人员表明，在干旱期间，灰尘对加州（CA）的内华达州山脉的土壤很重要，它从中央谷（CA）和中国的戈壁沙漠进入Sierra，这两个来源都带来了高营养的灰尘。这些结果是基于对最近2012-2016年干旱高峰期收集的灰尘的分析，提出了一个问题，即在潮湿的年份是否会观察到相同的趋势。在这里，该团队将在2017年夏季每月到每两个月收集新的灰尘样本，在2016-2017年的潮湿冬季之后，从之前研究中使用的南部Sierra临界区天文台的相同四个海拔高度。此外，他们将收集浅层表土样本进行比较。然后，他们将开始描述2017年以来灰尘和土壤的微生物群落，并分析2015年（干旱年）和2017年（湿润年）旱季进入塞拉利昂的灰尘的来源。这项研究将涉及三名研究生和一名博士后科学家，以及来自加州大学（UC）滨江和默塞德的服务不足的少数民族本科生，这两所大学都是西班牙裔服务机构。该项目将是教育和专业发展的绝佳机会。此外，参与的博士后科学家参加了加州大学欧文分校美国印第安人和阿拉斯加土著高中学生的地球系统科学住宅暑期研究所。该项目的研究成果将在暑期班期间传播，以使学生对气候与地球表面过程之间的相互作用产生兴趣。长期以来，灰尘一直被认为是缓慢侵蚀的热带生态系统的重要营养来源，强烈的风化限制了底层基岩的营养输入。调查人员最近沿着加州（CA）内华达州山脉的一个积极侵蚀的山地景观的工作揭示了来自区域和跨洋来源的大量灰尘;限制生长的营养物质（例如，磷）被确定为供应率与那些从下面的基岩风化。这项工作还表明，灰尘中的微生物群落在海拔之间变化，群落组成与共存的土壤群落几乎没有重叠序列。此外，从中央谷中海拔地区的贡献大幅增加，在夏季干旱期间，这表明，区域灰尘源，这些生态系统的相对重要性增加的时间，因为最后一次显着的降水事件增加。到目前为止，分析是基于最近2012-2016年干旱高峰期收集的灰尘输入（2014年），提出了一个问题，即调查结果是否对灰尘来源和排放的变化敏感。拟议的工作将开始，通过分析在另一个干旱年夏季（2015年）收集的灰尘的来源和营养成分来评估这个问题，并在2017年夏季收集新的样本，经过一个潮湿的一年，目标是在不久的将来分析它们。

Investigators have shown that, during drought, dust is important to soils in the Sierra Nevada, California (CA) and it is entering the Sierra from both the Central Valley (CA) and from the Gobi Desert, China, and that both sources bring in high-nutrient dust. These results are based on analyses of dust collected at the peak of the recent 2012-2016 drought, raising the question of whether the same trends would be observed during a wet year. Here, the team will collect new dust samples monthly to bi-monthly during the summer of 2017, following the recent wet winter of 2016-2017, from the same four elevations of the Southern Sierra Critical Zone Observatory that were used in previous research. In addition, they will collect shallow topsoil samples for comparison. They will then begin to describe the microbial community of the dust and soil from 2017, and to analyze the origin of dust entering the Sierra in the dry seasons of 2015, a dry year, and 2017, a wet year. The research will involve three graduate students and a postdoctoral scientist, as well as underserved minority undergraduates from both University of California (UC) Riverside and Merced, both Hispanic Serving Institutions. This project will be an excellent opportunity for educational and professional development. Additionally, the participating postdoctoral scientist takes part in a residential summer institute in Earth System Science for American Indian and Alaska Native high school students at UC Irvine. The research from this project will be disseminated during the summer institute in an effort to interest students in the interplay between climate and Earth surface processes. Dust has long been recognized as a vital source of nutrients in slowly eroding tropical ecosystems where intense weathering limits nutrient inputs from underlying bedrock. Investigators' recent work along an actively eroding montane landscape in the Sierra Nevada, California (CA) revealed large contributions of dust from both regional and transoceanic sources; growth-limiting nutrients (e.g., phosphorus) were determined to be supplied at rates on par with those from underlying bedrock weathering. This work also shows that microbial communities in dust varied between elevations, and community composition contained very few overlapping sequences with co-located soil communities. Also, the contributions from the Central Valley to mid-elevation sites increased substantially over the summer dry period, suggesting that the relative importance of regional dust sources to these ecosystems increases as the time since the last significant precipitation event increases. Analyses thus far have been based on dust inputs collected (2014) at the peak of the recent 2012-2016 drought, raising the question of whether findings are sensitive to changes in dust sources and emissions. The proposed work will begin to evaluate this question by analyzing the provenance and nutrients of dust collected during another drought-year summer (2015), and collecting new samples throughout the summer of 2017, after a wet year, with the goal of analyzing them in the near future.