CAREER: Microbial controls on wetland carbon stabilization and storage

--------------------------------------------------------------------------------------- 而湿地仅占地球陆地表面的7%左右,他们估计持有约40%的碳(C)。由于湿地植被生长速度快，微生物分解导致的土壤碳流失率一般较低，因此湿地在储存碳方面很有效。像许多生态系统一样，湿地通过农业径流的施肥而获得营养丰富。通常，施肥效应会增加微生物活动，导致微生物分解导致碳损失的增加。因此，湿地碳储量容易受到环境变化的影响，这反过来又会导致湿地补偿变化的能力降低。如果不考虑养分富集和微生物生理的影响，湿地C储存潜力可能被高估。这项研究将为微生物控制土壤C过程提供见解，这对能源、自然资源管理和保护方面的广泛国家利益具有影响。本研究通过研究微生物多样性、微生物代谢和c循环功能之间的关系，将推动生态系统科学、生态学和微生物学领域的发展。它还将通过专注于微生物多样性和K-12、本科和研究生阶段的课堂教育内容造福社会，这些内容将覆盖服务不足的人群，增强STEM劳动力的多样性。本研究将验证无机养分富集导致微生物群落从生长缓慢的寡养型向生长迅速的共养型转变的假设，从而导致土壤中微生物对碳和养分的处理发生变化。生态系统的改变可能导致土壤有机质（SOM）不稳定，这是由于受矿物质保护的SOM减少和呼吸速率增加，从而减少了湿地土壤C的储存。该项目的具体目标包括：(1)确定在一个历史上营养贫乏的湿地中，地上和地下植物生物量的变化与SOM积累的关系；(2)将微生物资源利用策略与环境和富营养化条件下的大气气体交换（甲烷、二氧化碳）和土壤有机质库联系起来；(3)研究微生物生物量、群落结构和代谢多样性的变化如何影响长期施肥对土壤有机质稳定性和碳储存潜力的影响。自2003年以来，在北卡罗来纳州沿海平原的一个营养贫乏的湿地生态系统中，重复施肥和干扰（通过割草）处理被应用。这个新项目将利用田间试验来确定持续施肥是否会影响植物-微生物关系和土壤C储存潜力。如果养分富集破坏了湿地C的储存，那么对湿地C库的预测可能被高估了，因为湿地经历了人类和温度诱导的养分富集。这项研究还将确定微生物群落的生理评估（用于表征贫营养和富营养分类群）是否比分类学或基于生物量的指标更能预测生态系统的响应。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

---------------------------------------------------------------------------------------While wetlands only occupy about 7% of Earth's land surface, they are estimated to hold about 40% of its carbon (C). Wetlands are effective at storing C due to their high rates of vegetation growth and generally low rates of soil C losses from decomposition by microbes. Like many ecosystems, wetlands are subjected to nutrient enrichment via fertilization from agricultural runoff. Often, fertilization effects can increase microbial activity, leading to higher rates of C loss through microbial decomposition. Thus, wetland C storage is vulnerable to changes in the environment, which, in turn, can result in a reduced capacity for wetlands to compensate for change. Wetland C storage potential could be overestimated when impacts of nutrient enrichment and microbial physiology are not incorporated into the earth-system context. This research will provide insights into microbial controls on soil C processes, which have implications for broad national interests in energy, natural resources management and conservation. This research will advance the fields of ecosystem science, ecology, and microbiology by examining the relationships among microbial diversity, microbial metabolisms, and C-cycling functions. It will also benefit society through classroom educational content focused on microbial diversity and processes at the K-12, undergraduate and graduate levels that will reach under-served populations, enhancing diversity of the STEM workforce. This study will test the hypothesis that inorganic nutrient enrichment causes shifts in microbial communities from slow growing oligotroph- to fast growing copiotroph-dominated assemblages, resulting in changes in microbial processing of C and nutrients in soils. An altered ecosystem may lead to soil organic matter (SOM) destabilization, due to decreased mineral-protected SOM and increased respiration rates, thereby reducing soil C storage in wetlands. The specific objectives of this project include: (1) determine how variation in above- and below-ground plant biomass relates to SOM buildup in a historically nutrient-poor wetland now experiencing nutrient enrichment; (2) relate microbial resource-use strategies to atmospheric gas exchange (methane, carbon dioxide), and soil organic matter pools under ambient and nutrient-enriched conditions; and (3) examine how shifts in microbial biomass, community structure, and metabolic diversity affect SOM stabilization and C storage potential due to long-term fertilization. Since 2003, replicated fertilization and disturbance (by mowing) treatments have been applied to a nutrient-poor wetland ecosystem in the North Carolina coastal plain. This new project will leverage the field experiment to determine whether ongoing fertilization influences plant-microbe relationships and soil C storage potential. If nutrient enrichment disrupts wetland C storage, then predictions for wetland C pools may be overestimated since wetlands experience both human and temperature-induced nutrient enrichment. This study will also determine whether physiological assessments of microbial communities (used to characterize oligotrophic and copiotrophic taxa) provide a better predictor of ecosystem responses than taxonomy or biomass-based metrics.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.