ETBC: Plant-microbe-mineral interaction as a driver for rock weathering and chemical denudation

植物和微生物通过释放有机化合物、二氧化碳和质子，改变岩土介质表面的组成，改变土壤水和溶质通量，以及固定致岩养分，来改变当地的风化环境。这项研究的目的是更好地了解植物对风化和剥蚀的影响。PIS建议测量植物-微生物相互作用如何影响四种不同岩石类型(玄武岩、花岗岩、片岩和流纹岩)的初始风化，以及这种风化导致化学剥蚀与生物量积累或溶解产物重新沉淀的程度。两种类型的高等植物将被用于重复的植物-微生物-岩石中附生实验：一种草物种(具有泡状丛枝菌根联合)和一种树种(具有外生菌根联合)。实验还将包括无植物(但微生物定植)和非生物(无菌)对照。一种假设是，植物的存在将增加风化作用，但减少剥蚀(即，与没有植物相比，我们将看到更多的矿物质转化，但从系统中损失的元素更少)。这意味着对土壤肥力和碳汇的重要反馈。将进行一系列环境控制的温室实验，包括测量玄武岩、花岗岩、流纹岩和片岩中的植物吸收、矿物转化和化学剥蚀，以及微生物和维管植物的存在和生长的影响。风化作用将根据剥蚀、生物吸收、吸附和次生矿物沉淀进行评估，其中每一项都将通过对生物量、水溶液和排泄物以及固相变化的详细表征来量化。实验结果将被用于生物地球化学模型的参数化。广泛的影响：这个项目将使两个合作的博士生得到培训，他们的论文研究将集中在生物地球化学、微生物生态学和植物生理生态学之间充满活力的界面上。研究将与国家临界区观测站(CZO)系统以及生物圈2(B2)相关的更广泛的努力密切协调，生物圈2(B2)是目前由亚利桑那大学管理的独特研究仪器。与B2和CZO的概念和实践联系将把受控良好的实验置于无法明确解决这些问题的平行领域和“宏观”研究的更广泛背景下。与B2和CZO的互动也将创造一个协作的环境，在这个环境中，博士生将被要求将他们的机械发现整合到更大规模(从泥土到山坡到集水区)的不断演变的理解中。B2，每年有5万名游客，将为公众提供一个引人注目的环境和强大的科研翻译场所。

Plants and microorganisms modify the local weathering environment by exuding organic compounds, CO2 and protons, altering the composition of geomedia surfaces, redirecting soilwater and solute fluxes, and immobilizing lithogenic nutrients. The goal of this study is to better understand the effects of plants on weathering and denudation. The PIs propose to measure how plant-microbe interactions affect the initial weathering of four distinct rock types (basalt, granite, schist, and rhyolite) and the extent to which this weathering results in chemical denudation versus biomass accumulation or re-precipitation of dissolution products. Two types of higher plants will be used in a replicated plant-microbe-rock mesocosms experiment: a grass species (with vesicular arbuscular mycorrhizal association) and a tree species (with ectomycorrhizal association). The experiments will also include plant-free (but microbially-colonized) and abiotic (sterile) controls.One hypothesis is that the presence of plants will increase weathering but decrease denudation (i.e., we will see more mineral transformation but less element loss from system in the presence versus absence of plants). This implies important feedbacks to soil fertility and C sequestration. A series of environmentally-controlled, greenhouse experiments will be conducted that involve measuring plant uptake, mineral transformation and chemical denudation in basalt, granite, rhyolite, and schist, as affected by presence and growth of microbiota and vascular plants. Weathering will be estimated based on denudation, bio-uptake, sorption, and secondary mineral precipitation, each of which will be quantified by detailed characterization of biomass, aqueous solution and effluxes, and solid phase changes. Experimental results will be used to parameterize a biogeochemical model.Broader Impacts: This project will enable the training of two collaborating Ph.D. students whose thesis research will focus on the vibrant interface between biogeochemistry, microbial ecology, and plant physiological ecology. Research will be closely coordinated with broader efforts associated with the National Critical Zone Observatory (CZO) system, and also with Biosphere2 (B2), a unique research instrument now managed by the University of Arizona. Conceptual and practical linkages with B2 and CZO will place the well-controlled experiments into a broader context of parallel field and "macrocosm" studies that are unable to address these questions unambiguously. Interaction with B2 and CZO will also create a collaborative environment where the Ph.D. students will be required to integrate their mechanistic findings into an evolving understanding manifested at larger (pedon to hillslope to catchment) scales. B2, which has fifty thousand visitors a year, will provide a compelling environment and powerful venue for research translation to the general public.