Iron geochemistry and controls on phosphorus bioavailability in northern peatlands

北极和亚北极泥炭地是高度敏感的生态系统，由于年气温的升高，这些生态系统正在经历植物覆盖、永久冻土融化和水饱和度的快速变化。预计这些变化将增加有机物的分解并释放温室气体。植物生长可以通过光合作用在陆地生态系统中固碳，并在短时间内减少向大气的释放，但植物生长增加抵消土壤碳损失的能力因土壤养分供应而变得复杂。特别是，关键的营养磷可能会越来越多地限制植物生长的需求超过目前的供应，但是，非生物控制磷的生物利用度仍然是北方泥炭地的主要知识差距。这项研究将调查高纬度土壤中磷生物有效性的地球化学控制，以评估冻原和北方生态系统作为大气温室气体未来汇的潜力。该项目将为研究生和本科生提供敏感和动态生态系统的研究培训。研究人员和他们的学生还将通过在克利夫兰自然历史博物馆开展土壤教育项目来参与社区外展活动。他们将通过实践活动向K-6学生及其家人讲授北极土壤、土壤多样性以及土壤作为自然资源的重要性。具体而言，PI将探索以下假设：高纬度地区的磷限制将因磷吸附到结晶不良的氢氧化铁而加剧，这些氢氧化铁在水文条件变化的情况下，在富含铁的泥炭地的广泛排水过程中迅速沉淀。植物磷的有效性强烈调节水文条件，由于氧化还原依赖的相互作用与铁羟基氧化物矿物。干燥土壤中铁结合磷的增加可能导致磷限制，从而限制植物生长并限制植物生物量中的碳储存。本研究的目的是整合地球化学分析（例如，耦合铁和磷提取）与同步辐射源光谱，以评估在阿拉斯加泥炭地实验（APEX）的实验操纵的洪水到排水良好的土壤梯度之间的铁和磷的地球化学协会。对冻土带长期观测站获得的土壤进行额外的地球化学分析（例如，图利克湖，巴罗环境观测站）和北方泥炭地（例如，Marcell实验森林）将为这项研究提供更广泛的背景。

Arctic and subarctic peatlands are highly sensitive ecosystems that are experiencing rapid changes in plant cover, permafrost thaw, and water saturation due to increasing annual temperatures. These changes are expected to increase organic matter decomposition and release greenhouse gases. Plant growth may sequester carbon in terrestrial ecosystems via photosynthesis and mitigate releases to the atmosphere over short time-scales, but the ability of increased plant growth to offset soil carbon losses is complicated by soil nutrient availability. In particular, the critical nutrient phosphorus may become increasingly limiting to plant growth as demand exceeds current supply; however, non-biological controls on phosphorus bioavailability remain a major knowledge gap for northern peatlands. This research will investigate geochemical controls on phosphorus bioavailability in high-latitude soils to evaluate the potential for tundra and boreal ecosystems to act as future sinks for atmospheric greenhouse gasses. The project will provide graduate and undergraduate students with research training in a sensitive and dynamic ecosystem. The investigators and their students will also engage in community outreach by running an educational program on soils at the Cleveland Museum of Natural History. They will use hands-on activities to teach K-6 students and their families about Arctic soils, soil diversity, and the importance of soil as a natural resource.Specifically, the PIs will explore the hypothesis that phosphorus limitation at high-latitudes will be exacerbated by phosphorus adsorption to poorly-crystalline iron oxyhydroxides that rapidly precipitate during widespread drainage of iron-rich peatlands under changing hydrologic regimes. Phosphorus availability to plants is strongly regulated by hydrologic conditions due to redox-dependent interactions with iron oxyhydroxide minerals. Increases in iron-bound phosphorus in drying soils may lead to phosphorus limitation that constrains plant growth and limits carbon storage in plant biomass. The objective of this research is to integrate geochemical analyses (e.g., coupled iron and phosphorus extractions) with synchrotron-source spectroscopy to evaluate geochemical associations between iron and phosphorus across an experimentally-manipulated gradient of flooded to well-drained soils at the Alaska Peatland Experiment (APEX). Additional geochemical analysis of soils obtained from long-term observatories in tundra (e.g., Toolik Lake, Barrow Environmental Observatory) and boreal peatlands (e.g., Marcell Experimental Forest) will provide broader context for this study.