ETBC Collaborative Research: Weathering Under Cover: Role of biofilms in mineral weathering and nutrient uptake in the mycorrhizosphere

知识价值：最近几个领域的进展为维管植物的生物地球化学机构的基于过程的研究奠定了基础，特别是它们的生理如何驱动地球？年代?风化引擎?从风化层中提取矿物质以形成土壤，化学剥蚀大陆，并在地质时间尺度上设定海洋/大气的化学成分。这样的研究是及时的，需要解释全球变化的土壤地质记录，并预测在人类改变的世界中，陆地碳封存对全球二氧化碳循环和土壤可持续性的影响。PIs的总体概念是，植物驱动的风化速率和机制是不同的，这取决于地质环境和生态系统阶段。他们把重点放在初级演代环境上，在那里植物必须通过化学风化从土壤中提取养分。前提是，许多植物对这些条件的关键适应是菌根圈生物膜的发育，它将根系附着在矿物表面上，并在根系-矿物界面上对风化和养分吸收的生物、化学和水文进行微定位。在这个微米尺度上，溶解和生物质量转移发生在非常小的距离上，并且与大块土壤水相对隔离，从而提高了宏观养分获取效率，减少了排水中的养分损失。中心假设是不同程度的营养限制（即从矿物来源提取碱性阳离子的需要）影响生物膜的发育和风化/吸收功能。为了解决这一假设，pi建议在生长实验中使用复制的外生菌根幼苗系统，并通过控制灌溉溶液和初始矿物质组成来改变土壤水和初级矿物质中Ca和K的有效性。这项研究将为微观尺度的矿物风化过程与生态系统尺度的养分获取过程以及最终全球尺度的大陆剥蚀过程之间的联系机制提供见解。更广泛的影响：8名本科生将参与这个项目。由于研究人员的独特组合，学生将从一所社区学院、一所四年制本科学院和两所研究型大学中选出。拟议的研究将促进科学家的合作网络，包括太平洋西北国家实验室、美国林业局、农业研究局和学术机构。研究结果将传播到科学网络，包括关键区域探索网络和哈伯德布鲁克生态系统研究，并通过为初中和高中教室设计的教学模块向公众介绍。最终，这项工作将成为改善植物营养和土壤可持续性以及更好地了解陆地和水圈碳封存的基础。

Intellectual merit: Recent advances across several fields set the stage for process-based research into the biogeochemical agency of vascular plants -- in particular, how their physiologies drive Earth?s ?weathering engine? to extract mineral matter from regolith to build soils, chemically denude the continents, and set the chemistry of the ocean / atmosphere on geologic timescales. Such research is timely andneeded to interpret pedo-geologic records of global change, and to forecast the effects of terrestrial C sequestration on the global CO2 cycle and soil sustainability in a human-altered world. The PIs overarching concept is that plant-driven weathering rates and mechanisms vary, depending on geologic setting and ecosystem phase. They focused on primary-successional settings, where plants must extract nutrients from soils by chemical weathering. The premise is that a key adaptation of many plants to these conditions is development of mycorrhizospheric biofilms, which attach the root system to mineral surfaces and micro-localize the biology, chemistry, and hydrology of weathering and nutrient uptake at the root system-mineral interface. At this micron scale, dissolution and biological mass transfers occur over very small distances and in relative isolation from bulk soil water, thereby increasing macroscopic nutrient acquisition efficiency and decreasing nutrient loss in drainage. The central hypothesis is that varying degreesof nutrient limitation (i.e., the need to extract base cations from mineral sources) influence biofilm development and weathering/uptake function. To address this hypothesis, the PIs propose to use replicated ectomycorrhizal seedling systems in a growth experiment, and vary the availability of Ca and K in bulk soil water and primary minerals by manipulating irrigation solutions and initial mineral composition. This research will provide insights into the mechanisms that link micron-scale processes of mineral weathering to ecosystem-scale processes of nutrient acquisition and ultimately global-scale processes of continental denudation.Broader Impact: Eight undergraduate students will work on this project. Because of the unique combination of researchers, students will be drawn from a community college, a four-year undergraduate college, and two research universities. The proposed research will foster a collaborative network of scientists that includes Pacific Northwest National Laboratory, the US Forest Service, the Agricultural Research Service, and academic institutions. The results will be disseminated to science networks including the Critical Zone Exploration Network and the Hubbard Brook Ecosystem Study, and introduced to the general public through teaching and learning modules designed for middle and high school classrooms. Ultimately, this work will serve as a foundation for improving plant nutrition and soil sustainability, and better understanding terrestrial and hydrospheric carbon sequestration.