ETBC: Collaborative Research: "The Effect of Climate on the Terrestial Sulfur Cycle"

智力价值：该提案旨在研究陆地 S 循环随降雨量从地球上最干燥的地区到最潮湿地区的变化方式。硫是生命中最重要的常量营养素之一，但人们对其“同伴”的了解却少之又少。然而，人类对全球硫循环扰动的程度、生态系统对硫作出反应的复杂方式，以及生命如何驱动主要元素循环行为的基本问题，使得对硫的研究成为一项有趣的科学和社会重要挑战。该项目将大气、地球化学和生态方面的专业知识结合在一起，量化生态系统中硫输入的来源和速率，探索土壤和植物内部硫循环的重要途径，并量化沿约 1 至约 4000 毫米 MAP y-1 降雨梯度的硫去除途径。该工作计划还包括测量多组气候梯度中的土壤和植物总硫和硫同位素，以了解气候对陆地硫储存和循环的影响。与 N 一样，假设在地球的湿端，S 循环主要由生物介导的氧化还原反应主导。随着降雨量减少到接近 0，并且植物和微生物达到可以忽略不计的水平，S 循环转向以无机过程为主，整个循环经历根本性转变。因此，这种降雨梯度提供了一个模板来说明我们受生物控制的星球的独特性，并更好地解释我们附近的类地行星火星的地球化学，火星表面有大量的硫酸盐积累。更广泛的影响：所使用的降雨梯度由一系列站点组成，这些站点是 NSF 资助的 CZEN 网络（关键区域探索网络）的一部分。该项目将从这些地点之前所做的工作中受益，其中一些工作对该项目的成功至关重要（水文和地球化学）。拟议的工作还将最终为 CZEN 网络数据库提供新的数据和信息。此外，CZEN 研究人员将成为该项目的合作者，加强这一新举措在地球科学领域的运作。该项目将主要涉及研究生，因此将为年轻学者提供培训和机会。然而，所涉及的广泛的科学专业知识将使这成为每个参与者特别令人兴奋和充满活力的学习环境。其次，这项研究将进一步促进 PI Amundson 与智利合作者的合作并协助国际交流。最后，该提案已提交给生物地球化学循环中的新兴主题，因为人们认为该项目涵盖了气候广度，最终使我们能够通过一般科学和教育渠道来说明真正独特的？但可变的？生命在我们星球历史上的作用。硫与氮和其他一些元素一起，带有明显的生命印记。只有通过对地球气候的全面审视（此处提出）或从太空（Sagan et al.1993. Nature 365:715-721）审视大局，才有可能传达地球的独特性和脆弱性（Amundson. 2008. Nature Geoscience 1:5-6）。

Intellectual Merit: This proposal intends to examine the manner in which the terrestrial S cycle varies with rainfall from the driest to the wettest parts of the planet. Sulfur, one of the most important macronutrients for life, is far less understood that its ?companion? element N. However, the magnitude of the human perturbation of the global S cycle, the complex ways in which ecosystems respond to S, and the basic question of how life drives the behavior of major elemental cycles makes a study of S an interesting scientific and societally important challenge. The project brings atmospheric, geochemical, and ecological expertise together to quantify the sources and rates of S inputs to ecosystems, to explore important avenues of internal S cycling within soils and plants, and quantify S removal pathways along a rainfall gradient from ~1 to ~4000 mm MAP y-1. The work plan also includes the measurement of total soil and plant S and S isotopes from multiple sets of climate gradients to learn about the patterns that climate imparts on terrestrial S storage and cycling. Like N, it is hypothesized that at the wet end of Earth the S cycle is dominated by biologically mediated redox reactions. As rainfall declines to near 0, and as plants and microbes reach negligible levels, the S cycle shifts to dominantly inorganic processes, and the entire cycle undergoes a fundamental transformation. This rainfall gradient therefore provides a template to illustrate the uniqueness of our biotically-controlled planet, and to better interpret the geochemistry of our nearby terrestrial planet Mars, which has large surficial sulfate accumulations. Broader Impacts: The rainfall gradient to be used is comprised of a series of sites that are part of the NSF funded CZEN network (Critical Zone Exploration Network). The project will benefit from the previous work done at these sites, some of which is critical to the success of this project (hydrology and geochemistry). The proposed work will also ultimately provide new data and information to the CZEN network database. Additionally, CZEN researchers will be collaborators on the project, strengthening the functioning of this novel initiative in geosciences. The project will largely involve graduate students, and will therefore provide training and opportunities for young scholars. However, the broad range of scientific expertise involved will make this an especially exciting and dynamic learning environment for everyone involved. Secondly, this research will further PI Amundson?s collaboration with Chilean collaborators and aid in international exchange. Finally, this proposal has been submitted to Emerging Topics in Biogeochemical Cycles because it is perceived that this project encompasses a climatic breadth that will allow us, in the end, to illustrate via general science and education outlets, the truly unique ? but alterable ? role of life on the history of our planet. Sulfur, along with N and some other elements, bears the unmistakable stamp of life. It is only by examining the big picture, via the sweep of Earth?s climate (proposed here), or from space (Sagan et al.1993. Nature 365:715-721), that it is possible to convey the uniqueness and fragility of Earth (Amundson. 2008. Nature Geoscience 1:5-6).