Chemical Hydrology of Vascular Plant Growth: Role of Root-Fungus Associations

径流的溶解化学负荷- -即从陆地环境向溪流、地下水和海洋排放的溶解物质- -对其与生态系统中营养物质的保留和损失、水生和海洋沿岸生境的质量以及海洋-大气系统施加的长期气候控制的关系很重要。维管植物促进原生矿物质的溶解或化学风化，以满足其生长所需的营养；长期以来，人们一直认为这种植物驱动的风化作用会影响土壤水分的化学成分和径流的化学负荷。这项研究将通过实验研究根系植物生长影响土壤水化学和径流中来自流域的矿物来源元素的水文损失的机制。我们之前对哈伯德布鲁克试验性生态系统的研究表明，相对于对照，松树的生长降低了生根区土壤水分中碱性阳离子的浓度，以及这些阳离子在排水中的排放。这项研究旨在调查矿物质到根的化学运输如何以及在什么条件下与土壤水隔离，并“保护”免受水文损失。据推测，这种现象是植物生长过程中根与矿物质附着的一种特征。我们特别假设外生菌根真菌和它们的菌丝网络作为根到矿物的管道，促进了我们在哈伯德布鲁克观察到的水化学控制。这一假设将在实验室和温室中通过重复的生长实验进行验证。这些实验将从水文、化学和生态简单的系统中分离出真菌和真菌根植物对溶液化学和排水损失的影响。此外，碱性阳离子将从它们在矿物表面的来源进入真菌和植物组织并进入排水系统。本研究的更广泛影响包括高中生和本科生，特别是女性，通过课程和兼职工作参与数据收集和解释；通过跨学科论坛和万维网传播研究成果；提高我们对长期生态系统可持续性的理解，以及对封存的大气二氧化碳分为短期和长期储存的控制。

The dissolved chemical load of runoff - i.e. discharge of dissolved mass from terrestrial environments to streams, groundwater and the oceans - is important for its relationship to nutrient retention and loss in ecosystems, quality of aquatic and marine coastal habitats, and long-term climate control exerted by the ocean-atmosphere system. Vascular plants promote dissolution of primary minerals, or chemical weathering, to meet their nutritional requirements for growth; this plant-driven weathering has long been understood to affect the chemistry of soil water and the chemical loading of runoff. This research will experimentally investigate the mechanisms by which rooted plant growth affects soil water chemistry and the hydrologic loss, in runoff, of mineral-derived elements from watersheds. Previous work by us on experimental ecosystems at Hubbard Brook indicates that pine tree growth reduces both soil-water concentrations of base cations in the rooting zone, and the discharge of these cations in drainage water, relative to controls. This research is designed to investigate how, and under what conditions, mineral-to-root chemical transport is isolated from soil water and "protected" from hydrologic loss. It is hypothesized that this phenomenon is a feature of root-to-mineral attachment which occurs during plant growth. It is specifically hypothesized that ectomycorrhizal fungi and their hyphal networks function as root-to-mineral conduits which facilitate the hydrochemical control observed by us at Hubbard Brook. The hypothesis will be tested by replicated growth experiments in the laboratory and in greenhouses. The experiments will isolate fungal and fungi-root-plant effects on solution chemistry and loss in drainage from hydrologically, chemically and ecologically simple systems. Additionally, base cations will be tracked from their sources at mineral surfaces into fungal and plant tissue and into drainage. Broader impacts of this research include participation of high school and undergraduate students, particularly women, in data collection and interpretation via coursework and part-time jobs; dissemination of findings via interdisciplinary forums and the world wide web; and improvement of our understanding of long-term ecosystem sustainability and controls on the partitioning of sequestered atmospheric CO2 into short-term and long-term storage.