Collaborative Research: Biological and geochemical controls on phosphorus bioavailability in arctic tundra

磷是生命必需的营养物质，但在某些环境中，它供应不足，限制了植物的生长和分解。植物和微生物以溶解磷酸盐的形式从土壤中的水中吸收磷，磷酸盐也可以通过与土壤矿物质结合而从溶液中去除。特别是，氧化铁矿物强烈结合磷酸盐，并可能调节其对植物和微生物的可利用性。该项目将研究地球化学和生物系统如何在阿拉斯加Toolik Field Station附近的北极冻土带土壤中争夺磷酸盐，那里的土壤变暖和永久冻土融化正在改变碳和水的收支，从而影响土壤水分和养分的有效性。这项研究将确定土壤特性如何影响对磷酸盐的竞争，并对北极陆地生态系统中的植物生长和碳动态产生广泛影响。该项目还支持两名早期职业科学家，一名博士后学者，以及多名研究生和本科生。此外，所有参与者将设计数据驱动的教育活动（DataNuggets），这些活动将用于跨多个平台交流科学成果。陆地生态系统储存碳的能力在很大程度上取决于养分供应，而养分供应会影响植物的生长和分解速度。磷通常是一种限制性营养物质，人们普遍认为冻土带生态系统中的磷循环主要是通过生物途径进行的，其中生物对磷的需求是通过有机分子中磷的酶释放来满足的。然而，这一概念模型并没有考虑到铁（Fe）氧化物，它可能作为营养陷阱调节磷酸盐的溶解度，并在不同的氧化还原条件下作为P源或汇，即使在有机土壤中也是如此。不同环境条件下控制氧化结合磷的数量和生物利用度的过程尚不清楚，这限制了我们预测磷有效性如何随预期水文变化而变化的能力。波动的氧化还原条件驱动铁氧化物的微生物转化，也可能调节磷的生物利用度。因此，生物和地球化学对磷动力学的控制可能随着北极景观的水文和氧化还原制度而变化。该项目将使用传感器网络来表征低北极苔原典型环境中的氧化还原和pH模式，并研究这些梯度中的生物和地球化学P竞争。研究人员将量化磷在非生物（铁氧化物和其他矿物质）和生物（微生物和植物）之间的竞争性分配。他们将测试地球化学吸收和共沉淀过程与植物根系和微生物在冻土带土壤中有效竞争磷酸盐的假设。该研究将首次评估地球化学与生物控制对磷生物利用度的重要性，以及这些敏感生态系统中水文变化如何改变它们。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。

Phosphorus is an essential nutrient for life, but in some environments it is in short supply, putting limits on plant growth and decomposition. Plants and microorganisms take up phosphorus from the water in soil in the form of dissolved phosphate, which can also be removed from solution by binding to soil minerals. In particular, iron oxide minerals strongly bind phosphate and may regulate its availability to plants and microorganisms. This project will investigate how geochemical and biological systems compete for phosphate in arctic tundra soils near Toolik Field Station, Alaska, where soil warming and permafrost thaw are altering carbon and water budgets, which in turn affect soil moisture and nutrient availability. This research will determine how soil properties can affect this competition for phosphate, with broad consequences for plant growth and carbon dynamics in Arctic terrestrial ecosystems. This project also supports two early career scientists, a postdoctoral scholar, and multiple graduate and undergraduate students. Furthermore, all participants will design data-driven educational activities (DataNuggets), which will be used to communicate scientific results across multiple platforms.The ability of terrestrial ecosystems to store carbon depends largely on nutrient availability, which affects both plant growth and decomposition rates. Phosphorus (P) is often a limiting nutrient, and P cycling in tundra ecosystems is widely assumed to occur primarily through biological pathways, in which biological P demand is met by enzymatic release of phosphate from organic molecules. However, this conceptual model does not account for iron (Fe) oxides, which may serve as nutrient traps that regulate phosphate solubility and serve as P sources or sinks under different redox conditions, even in organic soils. The processes controlling the quantity and bioavailability of oxide-bound P under different environmental conditions remain unclear, limiting our ability to predict how P availability might change with expected hydrological changes. Fluctuating redox conditions drive microbial transformation of Fe oxides and may also regulate P bioavailability. Thus, biological and geochemical controls over P dynamics may vary as a function of hydrology and redox regime across arctic landscapes. This project will use a sensor network to characterize redox and pH patterns in environments typical of low-arctic tundra and investigate biological and geochemical P competition across these gradients. The investigators will quantify competitive partitioning of P between abiotic (Fe oxides and other minerals) and biotic (microbial and plant) sinks. They will test the hypothesis that geochemical sorption and co-precipitation processes effectively compete with plant roots and microorganisms for phosphate in tundra soils. The study will provide the first assessment of the importance of geochemical versus biological controls on P bioavailability and how they might be altered by hydrological changes in these sensitive ecosystems.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.