Iron Redox Biogeochemistry: Controls on Carbon and Phosphorus Cycling in Humid Tropical Forests

DEB 0543558 w。L. Silver， M. K. Firestone，和G.碳在全球气候变化中起着核心作用，湿润热带森林中生物群的生长、死亡和分解对全球碳循环有重大影响。热带森林主要生长在高风化的富铁低磷土壤上。磷被认为是热带地区最常见的限制净初级生产力的养分。然而，模拟研究表明，植被使用的磷比土壤中可用的磷要多得多。铁矿物在好氧条件下可以固存磷，在厌氧条件下通过铁还原释放磷。在厌氧期间，铁的还原也可能显著促进二氧化碳（一种温室气体）的释放。波动的氧化还原条件在这些土壤中很常见，允许铁在缺氧期间迅速再生，并在缺氧阶段驱动磷和二氧化碳的释放。本研究的总体假设是，铁的氧化还原生物地球化学和微生物学为理解高风化土壤中磷的生物有效性悖论和磷碳循环提供了关键。该项目将培训波多黎各高中生进行实地科学研究，并资助暑期研究实习，作为Geballe本科生研究机会项目的一部分。该研究还将培养2名本科生、2名研究生和2名博士后科学家。

DEB 0543558W. L. Silver, M. K. Firestone, and G. SpositoIron Redox Biogeochemistry: Controls on Carbon and Phosphorus Cycling in Humid Tropical Forests Carbon plays a central role in global climate change, and the growth, death, and decomposition of biota in humid tropical forests have a large impact on the global carbon cycle. Tropical forests dominantly occur on highly weathered soils rich in iron and low in phosphorus. Phosphorus is considered the nutrient most commonly limiting to net primary productivity in the tropics. Modeling studies, however, suggest that the vegetation uses considerably more phosphorus than is thought to be available in soils. Iron minerals can sequester phosphorus under aerobic conditions, and release it via iron reduction under anaerobic conditions. Iron reduction may also contribute significantly to the release of carbon dioxide, a greenhouse gas, during anaerobic periods. Fluctuating redox conditions are common in these soils, allowing iron to be rapidly regenerated during oxic periods and drive phosphorus and carbon dioxide release during the anoxic phases. The overarching hypothesis of the proposed research is that the redox biogeochemistry and microbiology of iron provide a key to understanding the phosphorus bioavailability paradox and the cycling of phosphorus and carbon in highly weathered soils.This project will train Puerto Rican high school students in field-based scientific research, and help fund summer research apprenticeships as part of the Geballe Research Opportunities for Undergraduates Program. The proposed research will also train two undergraduate students, two graduate students, and two post doctoral scientists.