Collaborative research: Controls of climate and dust on soil chemical erosion and nutrient supply

土壤是地球表面环境的重要组成部分。它们是维持生命的养分仓库，它们为动植物提供栖息地，它们通过在全球碳循环中的作用影响地球气候。该项目的主要目标是量化气候和沙尘对土壤化学侵蚀率和土壤养分含量的影响。这一点很有意思，因为化学侵蚀加速了地貌演变并调节了地球气候，也因为尘埃是土壤养分的关键来源。为了调查这些相互关联的现象，该项目将在加利福尼亚州圣哈辛托峰的两个垂直横断面上建立一系列研究地点，在那里，近3公里的起伏造成惊人的气候梯度，年平均温度范围为18摄氏度。这项工作将支持一个由两名早期职业教师(一名女性，两人都是终身教职前)组成的团队，并将通过PI团队的支持(其中一人是代表不足的群体(阿拉斯加原住民)的成员)，以及通过面向代表不足的群体的学生的校园方案招收学生，来促进多样性倡议。外展和教育活动将集中于与圣地亚哥县教育办公室和威斯康星大学地质博物馆的专家合作，为中学教师开发资源。尽管长期以来人们预计气候应该强烈影响化学侵蚀速度，但事实证明，量化这些影响在自然界中是困难的，部分原因是这些影响很难测量，部分原因是岩性和粉尘等其他因素可能会掩盖气候影响。粉尘对土壤养分供应的影响也同样是一个持续存在争议的话题，部分原因是它取决于土壤生产和化学侵蚀的速度，而这两个因素很少在与粉尘沉积速度相同的地方进行测量。拟议的工作将通过结合对SJP的化学侵蚀速率、气候、尘埃沉积速率和来源的测量来避免这些问题，SJP的温度范围是美国单一未冰川岩性中最大的。这将建立在以前工作的基础上，通过在基岩、土壤、尘埃和植被中应用新的放射性同位素测量。这些数据将量化化学侵蚀速率对气候的敏感性，并为粉尘对土壤养分供应影响的时空变化提供新的见解，这在本工作将针对的季节时间尺度上没有得到很好的限制。更广泛地说，这项工作有可能消除理解地球地形、表面化学和尘埃循环如何在空间可变的气候下演变的障碍--这是地球山脉的共同特征。最终，这些对美国最引人注目的气候梯度之一的测量应该会指导未来的努力，将气候和尘埃明确地纳入地球表面的地形和化学演化模型中。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Soils are a critical component of Earth’s surface environment. They are storehouses of nutrients that sustain life, they provide habitats for plants and animals, and they influence Earth’s climate through their role in the global carbon cycle. This project’s main goal is to quantify how climate and dust affect soil chemical erosion rates and soil’s nutrient content. This is of interest because chemical erosion accelerates landscape evolution and modulates Earth’s climate, and because dust is a key source of nutrients to soils. To investigate these linked phenomena, this project will establish a series of study sites along two altitudinal transects at San Jacinto Peak, California, where nearly 3 km of relief creates a striking climate gradient with a range in mean annual temperature of 18 degrees C. This work will support a team of two early career faculty (one female, both pre-tenure), and will promote diversity initiatives through the support of the PI team, one whom is a member of an underrepresented group (Alaska Native), as well as through the recruitment of students via on-campus programs for students from underrepresented groups. Outreach and education activities will focus on developing resources for middle school teachers in collaboration with experts at the San Diego County Office of Education and the University of Wisconsin Geology Museum.Despite longstanding expectations that climate should strongly affect chemical erosion rate, quantifying these effects in nature has proven difficult, partly because these rates are difficult to measure, and partly because other factors like lithology and dust can obscure climatic effects. Dust’s impact on soil nutrient supply is likewise an ongoing topic of contention, partly because it depends on rates of soil production and chemical erosion, which are rarely measured in the same places that dust deposition rates are. The proposed work will avoid these issues by combining measurements of chemical erosion rates, climate, and dust deposition rates and provenance at SJP, which spans the largest range in temperature within a single unglaciated lithology in the United States. This will build on previous work by applying novel radiogenic isotope measurements in bedrock, soil, dust and vegetation. These data will quantify the sensitivity of chemical erosion rates to climate and provide new insights into spatial and temporal variations in dust’s impact on soil nutrient supply, which is not well constrained at the seasonal time scales that will be targeted in this work. More broadly, this work has the potential to remove a barrier to understanding how Earth’s topography, surface chemistry, and the dust cycle evolve under spatially variable climates—a common feature of Earth’s mountain ranges. Ultimately, these measurements across one of the most striking climate gradients in the United States should guide future efforts to include climate and dust explicitly in models of the topographic and chemical evolution of the Earth’s surface.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.