Impact of long-term N deposition on nitrogen transformation and translocation in a northern peatland

大面积的泥炭地暴露在大气氮沉降升高的环境中。当长期持续的氮输入导致“氮饱和”时，土壤中氮流失，不可避免地会造成环境污染。疏营养型泥炭地以泥炭为主，完全由干湿大气沉降提供养分，对大气氮输入的增加非常敏感。因此，研究人为氮输入引起的氮质量平衡和循环的变化具有重要的科学意义。目前对长期氮污染后氮的命运和流动性的变化知之甚少。本项目拟通过15N同位素示踪剂联合应用和HYDRUS模型，阐明不同长期养分施肥和植物覆盖变化下不同池中N的转化和迁移途径。通过实证分析和建模，阐明土壤和植物对氮素的保留机制，并估算氮素饱和阈值。本研究结果将提高我们对氮在增加负荷下的命运的认识，从而提高我们预测北方泥炭地氮平衡和循环未来响应的能力。

Large areas of peatlands have been exposed to elevated atmospheric N deposition. When sustained chronic inputs of N lead to “nitrogen saturation”, N is lost from the soil, and environmental pollution will inevitably occur. Ombrotrophic, Sphagnum-dominated peatlands are exclusively fed by wet and dry atmospheric deposition and are very sensitive to increased atmospheric N input. It is thus of great scientific interest to examine the changes in N mass balances and cycling induced by anthropogenic N input. Little is currently known about the changes in the fate and mobility of N following chronic N pollution. The proposed project seeks to clarify the pathways of N transformations and N mobility in different pools under different long-term nutrient fertilization and changing plant cover through combined application of 15N as an isotopic tracer and HYDRUS modeling. The mechanisms of N retention by soil and plants will be elucidated and N saturation thresholds will be estimated by empirical analyses and modeling. Results from this study will improve our understanding of the fate of N under increasing N load, thereby enhance our ability to predict the future response of the N balance and cycle in northern peatlands.