CAREER: Microbial controls on wetland carbon stabilization and storage

---------------------------------------------------------------------------------------While湿地只占地球陆地表面的7%，据估计它们持有约40%的碳(C)。湿地在储存碳方面是有效的，因为它们的植被生长率很高，而微生物分解土壤碳的损失率通常很低。像许多生态系统一样，湿地通过从农业径流中施肥来获得养分的丰富。通常，施肥效应会增加微生物的活性，导致微生物分解导致更高的碳损失率。因此，湿地的碳储存很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。如果没有将营养丰富和微生物生理学的影响纳入地球系统环境中，湿地的碳储存潜力可能被高估。这项研究将对土壤碳过程中的微生物控制提供见解，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。这项研究将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，推动生态系统科学、生态学和微生物学领域的发展。它还将通过侧重于K-12、本科生和研究生一级的微生物多样性和过程的课堂教育内容造福社会，这些内容将惠及服务不足的人群，增强STEM劳动力的多样性。这项研究将检验这一假说，即无机养分的增加导致微生物群落从生长缓慢的寡养菌转变为快速生长的共养菌群，从而导致土壤中C和养分的微生物处理发生变化。生态系统的改变可能会导致土壤有机质(SOM)的不稳定，因为受矿物保护的SOM减少，呼吸速率增加，从而减少湿地土壤C的储存。该项目的具体目标包括：(1)确定在经历营养丰富的历史贫瘠湿地中，地上和地下植物生物量的变化与土壤有机质积累的关系；(2)将微生物资源利用战略与环境和营养丰富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)研究由于长期施肥，微生物生物量、群落结构和代谢多样性的变化如何影响土壤有机质的稳定和碳储存潜力。自2003年以来，重复施肥和干扰(通过割草)处理已经应用于北卡罗来纳州沿海平原营养不良的湿地生态系统。这个新项目将利用田间试验来确定正在进行的施肥是否会影响植物与微生物的关系和土壤碳的储存潜力。如果营养丰富扰乱了湿地的碳储存，那么对湿地碳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营养丰富。这项研究还将确定微生物群落的生理学评估(用于表征寡养和共养分类群)是否比分类学或基于生物量的度量方法提供更好的生态系统响应预测。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。

---------------------------------------------------------------------------------------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.