Collaborative research: Defining the scope and consequences of ectomycorrhizal fungal control on forest organic matter decomposition

真菌在森林生态系统中发挥着至关重要的作用，分解掉落在森林地面上的落叶和木质碎片。随着这种有机物被真菌分解，其中大部分被并入土壤，增加了它们所蕴藏的大量碳和氮库。越来越多的人认识到，外生菌根真菌与许多林木形成营养共生关系，可以减缓有机质的分解，稳定土壤碳。这项研究旨在严格评估外生菌根真菌如何抑制有机质分解，并表征这种抑制对土壤碳和氮动态的影响。确定外生菌根真菌在有机质分解过程中如何调节碳和养分通量，将有助于以土壤碳保持和树木健康为重点的森林管理。此外，确定外生菌根真菌在不同温度和湿度条件下抑制有机物分解的范围对于准确地制定地球系统模型中的碳和氮动态将是重要的。该项目通过与雪松溪生态系统科学保护区、分钟地球、加州科学院和佛罗里达自然历史博物馆的合作，为科学、技术、工程和数学(STEM)研究生和本科生指导、K-12体验式学习以及公众参与提供支持。外生菌根真菌改变有机质分解的能力取决于三个因素：有机质化学、外生菌根真菌群落组成和环境条件。这一假设将在明尼苏达州、佛罗里达州和加利福尼亚州的研究地点进行一系列基于现场的实验来验证。通过利用明尼苏达州的一个单一研究地点，在不同的外生菌根真菌群落组成的森林中同时部署多种有机质类型，在保持多个环境变量不变的情况下，可以确定有机质化学和外生菌根真菌群落组成的独立和交互作用。同时，通过在温度和降水不同的多个地点(明尼苏达州、佛罗里达州和加利福尼亚州)部署一种共同的有机质类型，也可以评估土壤条件的变化对外生菌根真菌抑制有机分解的影响程度。此外，对不同土壤组分中碳的详细分析将提供外生菌根真菌引起的有机质分解率变化和土壤中碳保持之间的关键缺失环节。该奖项反映了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。

Fungi play an essential role in forest ecosystems, breaking down leaf litter and woody debris that has fallen to the forest floor. As this organic matter is decomposed by fungi, much of it is incorporated into soils, adding to the significant carbon and nitrogen pools they harbor. There is growing recognition that ectomycorrhizal fungi, which form nutritional symbioses with many forest trees, can slow the breakdown of organic matter and stabilize soil carbon. This research seeks to critically assess how ectomycorrhizal fungal suppress organic matter decomposition, and to characterize the impacts of this suppression on soil carbon and nitrogen dynamics. Determining how ectomycorrhizal fungi mediate carbon and nutrient fluxes during the decomposition of organic matter will be useful for forest management focused on carbon retention in soils and on tree health. In addition, defining the scope of ectomycorrhizal fungal suppression of organic matter decomposition across diverse temperature and moisture conditions will be important for accurately formulating carbon and nitrogen dynamics in Earth system models. This project provides support for science, technology, engineering and math (STEM) graduate and undergraduate mentoring, K-12 experiential learning, and public engagement through collaborations with the Cedar Creek Ecosystem Science Reserve, Minute Earth, California Academy of Sciences, and the Florida Museum of Natural History. The capacity of ectomycorrhizal fungi to modify organic matter decomposition is hypothesized to depend on three factors: organic matter chemistry, ectomycorrhizal fungal community composition, and environmental conditions. This hypothesis will be tested with a series of field-based experiments at research sites in Minnesota, Florida, and California. By utilizing a single research site in Minnesota in which a wide range of organic matter types are concurrently deployed across forest stands differing in ectomycorrhizal fungal community composition, the independent and interactive roles of organic matter chemistry and ectomycorrhizal fungal community composition can be determined while holding multiple environmental variables constant. At the same time, by deploying a common organic matter type across multiple sites varying in temperature and precipitation (in Minnesota, Florida, and California), the extent to which variation in edaphic conditions influence ectomycorrhizal fungal suppression of organic decomposition can also be assessed. Additionally, detailed analyses of the carbon held in various soil fractions will provide a critical missing link between ectomycorrhizal fungal-induced changes in organic matter decomposition rates and retention of carbon in soil.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.