RAPID: Gauging the impacts of California's 500-year drought on aeolian inputs to mountain soils and ecosystems

越来越多的证据表明，加州目前正在经历自1580年以来最严重的干旱，但随着气候变化，这样的干旱很可能会变得更加常见。任何干旱，特别是这种规模的干旱，都可能使尘埃从休耕农田和裸露的自然生态系统转移到有时很远的地方。正在运输的尘埃可能会带来营养物质和微生物，对尘埃所在的生态系统产生未知的、但潜在的变革性影响。该项目建议通过测量沙尘增加对内华达山脉的生态系统影响来利用当前干旱的独特极端。调查人员将测量输送到Sierras的粉尘的数量和微生物组成。合作者将确定尘埃的来源(使用同位素化学)和化学成分。在未来，调查人员将努力将在今年极端干旱期间迅速收集的数据与将在多雨年份收集的数据进行比较。将在南塞拉利昂临界区天文台(SSCZO)沿海拔梯度的四个地点收集尘埃，海拔从400米到2700米不等。在每个地点，将从被动式除尘器和涡流协方差塔主动二氧化碳采样器上的过滤器(孔径为1微米)每月收集粉尘至2014年11月，并在2015年春季再次收集粉尘。为了补充尘埃收集，将在塔楼的占地面积内收集土壤样本(10厘米深)。粉尘样品的来源将使用放射性锶(Sr)和钕(ND)同位素示踪剂来确定。还将分析粉尘和土壤样本的营养物质和微生物组成。这一办法将有助于确定特大干旱对以下方面的影响：i)与粉尘有关的对土壤和生态系统的地球生物学和生物地球化学的贡献；ii)微生物，包括细菌、古菌和真菌等的本地和远程粉尘来源以及内华达山脉营养物质的作用；以及iii)海拔在确定巨型干旱引起的粉尘运输的生态影响方面的作用。

Mounting evidence shows that California is currently experiencing the most severe drought since 1580, yet it is likely that droughts such as these will become more common as the climate changes. Any drought, particularly one of this magnitude, can elevate dust transport, from fallow croplands and bare natural ecosystems, to sometimes distant locations. The dust being transported may bring nutrients and microorganisms, with unknown, but potentially transformational, impacts on the ecosystems where the dust is deposited. This project proposes to take advantage of the unique extremity of the current drought by measuring the ecosystem impact of increased dust to the Sierra Nevada mountains. The investigator will measure the amount and microbial composition of dust transported to the Sierras. Collaborators will determine the origin (using isotopic chemistry) and chemical makeup of the dust. In the future, the investigator will endeavor to compare the data rapidly collected during this year of extreme drought to data to be collected in wetter years. Dust will be collected at four sites along an elevational gradient in the Southern Sierra Critical Zone Observatory (SSCZO), ranging from 400 m to 2700 m elevation. At each site, dust will be collected monthly through November 2014, and again in Spring 2015, from passive dust collectors and from filters (1 um pore size) on the Eddy Covariance Towers active CO2 samplers. To complement dust collection, soil samples (10 cm depth) will be collected within the footprint of the towers. The origin of dust samples will be determined using radiogenic strontium (Sr) and neodymium (Nd) isotopic tracers. Nutrients and microbial composition of dust and soil samples will also be analyzed. This approach will allow to identify the effects of mega-droughts on i) dust-related contributions to the geobiology and biogeochemistry of soils and ecosystems, ii) the role of local versus distant dust sources of microorganisms, including bacteria, archaea and fungi, and of nutrients to the Sierra Nevada, and iii) the role of elevation in determining the ecological effects of mega-drought-induced dust transport.