Collaborative Research: How iron states impact temperature sensitivity of heterotrophic respiration in humid tropical soils

潮湿的热带森林调节着地球的气候，因为它们有能力吸收大量的大气二氧化碳并将其储存在植被和土壤中。这些森林也是受气候变化（如全球变暖）影响最大的森林。温度升高可能导致热带土壤释放更多的二氧化碳，进一步导致大气变暖。这项研究评估了温度升高如何影响土壤中二氧化碳的释放，特别是土壤微生物通过一种称为异养呼吸的过程产生的二氧化碳。这项研究推进了我们对调节土壤微生物功能及其二氧化碳产生的基本过程的理解，以及影响土壤储存和稳定二氧化碳能力的机制。这项工作对环境科学家、工程师和政策制定者评估气候变化减缓和适应战略（如重新造林和植树造林）具有重要意义。该项目支持在微生物学、水文学、环境科学和工程的交叉领域开发新的跨学科课程材料，让初中和高中学生了解气候变化对热带森林的影响，并培训不同的学生。这项工作评估了铁循环和土壤碳之间的相互作用如何随着时间的推移调节异养呼吸的温度敏感性。本研究的指导假设是，短期土壤有机碳分解通过铁还原增加异养呼吸的温度敏感性。从长期来看，微生物群落的适应和铁矿物对有机碳的物理化学保护降低了温度敏感性。该项目结合了实验和基于过程的建模，利用热带对气候变化的反应实验（TRACE），这是波多黎各卢基略雨林中最先进的野外变暖实验。对从TRACE的对照地块和温暖地块中取样的土壤进行的综合实验揭示了它们对温度梯度和铁状态变化的生物地球化学反应。一个基于过程的土壤模型应用于分析观测和机械地解释温度变化的响应。这个奖项反映了NSF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。

Humid tropical forests regulate the Earth’s climate, due to their capacity to absorb large amounts of atmospheric carbon dioxide and store it in vegetation and soils. These forests are also the most impacted by changes to the climate, such as global warming. An increase in temperature may cause tropical soils to release more carbon dioxide, further contributing to warming of the atmosphere. This research evaluates how an increase in temperature can affect the release of carbon dioxide from soils, specifically carbon dioxide produced by soil microorganisms through a process called heterotrophic respiration. The research advances our understanding of the fundamental processes that regulate the functioning of soil microorganisms and their production of carbon dioxide, as well as the mechanisms that affect the ability of soils to store and stabilize carbon dioxide. The work has important implications for environmental scientists, engineers, and policy makers working to assess climate change mitigation and adaptation strategies, such as reforestation and afforestation. The project supports the development of new interdisciplinary curricular material at the intersection of microbiology, hydrology, environmental science and engineering, engages middle and high school students around the impacts of climate change to tropical forests, and trains diverse students.Iron is a relatively abundant mineral in humid tropical soils. This work evaluates how the interactions between iron cycles and soil carbon modulate the temperature sensitivity of heterotrophic respiration over time. The research is guided by the hypothesis that short-term soil organic carbon decomposition through iron reduction increases the temperature sensitivity of heterotrophic respiration. In the long-term, it is hypothesized that both microbial community adaptation and physicochemical protection of organic carbon by iron minerals reduce the temperature sensitivity. The project combines experiments and process-based modeling, leveraging the Tropical Responses to Altered Climate Experiment (TRACE), a state-of-the-art field warming experiment in the Luquillo Rainforest in Puerto Rico. Comprehensive experiments with soils sampled from control and warmed plots at TRACE inform their biogeochemical response to temperature gradients and changing iron states. A process-based soil model is applied to analyze observations and mechanistically explain the response to changing temperatures. The project includes training at the undergraduate, graduate student and postdoctoral levels.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.