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，但随着气候的变化，这样的干旱很可能会变得更加普遍。任何干旱，尤其是这种程度的干旱，都会增加沙尘的运输，从休耕的农田和光秃秃的自然生态系统，有时会到遥远的地方。移动的尘埃可能带来营养物质和微生物，对尘埃沉积的生态系统产生未知但可能具有变革性的影响。该项目建议利用当前干旱的独特极端，通过测量内华达山脉增加的灰尘对生态系统的影响。研究人员将测量运送到塞拉山脉的尘埃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）和化学组成。未来，研究者将努力将今年极端干旱期间迅速收集的数据与湿润年份收集的数据进行比较。在海拔400米至2700米的南部塞拉临界带观测站（SSCZO），沿海拔梯度的四个地点将收集尘埃。在每个站点，从2014年11月到2015年春季，将从被动收集器和涡流协方差塔主动CO2采样器上的过滤器（孔径为1微米）收集粉尘。为了补充灰尘收集，将在塔的足迹范围内收集土壤样本（10厘米深）。尘埃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。还将分析灰尘和土壤样品的营养成分和微生物组成。这种方法将能够确定特大干旱对以下方面的影响：(1)与沙尘有关的土壤和生态系统的地球生物学和生物地球化学贡献；(2)本地与远处的微生物沙尘来源的作用，包括细菌、古细菌和真菌，以及内华达山脉的营养物；(3)海拔高度在确定特大干旱引起的沙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.