Hydrologic influences on soil trace gas fluxes across complex terrain

控制一氧化二氮和甲烷进出土壤通量的物理和微生物过程在空间和时间上变化很大，并直接和间接受到土壤含水量的控制，而土壤含水量在很大程度上受水文过程的控制。该项目的目标是评估水文动力学的影响，换句话说，流域尺度的水再分配，对土壤-大气微量气体通量在山区景观。将使用一氧化二氮、甲烷和二氧化碳通量测定、土壤含水量和再分配测量、潜在反应物化学分析、数字地形分析和水文监测相结合的方法，评估蒙大拿州森林流域对微量气体通量空间和时间动态的环境控制。揭示山地生态系统中微量气体源和汇与水文特性之间的关系。该项目将测试现有的地形分析框架，该框架使用基于水文属性的景观单元（与溪流相关的斜坡位置、坡向、排水面积等）将点尺度的痕量气体测量转换为景观尺度。该项目建立在先前和正在进行的美国国家科学基金会资助的关于山区生态系统中二氧化碳通量的水文控制的研究基础上，并利用现有的现场基础设施和技术资源。一氧化二氮和甲烷，像二氧化碳一样，是放射性活跃的微量气体，对全球变暖有重大影响。众所周知，北美的山地森林生态系统是一个重要的碳汇。然而，山地森林生态系统对大气变暖潜势的净影响尚不清楚，因为其他微量气体的净通量尚不清楚。这在一定程度上是因为将点微量气体通量测量转化为整个景观的有效方法尚未为此类系统开发出来。该项目将开发和测试的方法有可能在景观尺度上改善山地森林生态系统的温室气体净排放估算。温室气体排放政策制定中考虑的空间尺度。此外，该研究项目将提供多个空间和时间尺度的陆地-空气二氧化碳、氧化亚氮和甲烷通量数据，这将对对基准模型感兴趣的科学家有用。蒙大拿州立大学将为研究生和本科生提供水文学和生物地球化学方面的实地实践培训机会。

The physical and microbiological processes governing nitrous oxide and methane fluxes to and from soil are highly variable in space and time and are controlled, directly and indirectly, by soil moisture content, which is largely governed by hydrologic processes. The goal of this project is to evaluate the impact of hydrological dynamics, in other words catchment scale water redistribution, on soil-atmosphere trace gas fluxes across a mountain landscape. A combination of nitrous oxide, methane and carbon dioxide flux determinations, soil water content and redistribution measurements, chemical assays of potential reactants, digital terrain analyses and hydrological monitoring will be used to assess the environmental controls on trace gas flux spatial and temporal dynamics in a forested Montana watershed. Relationships between trace gas sources and sinks and hydrologic properties in montane ecosystems will be uncovered. This project will test an existing topography analysis framework that uses hydrologic property based landscape units (slope position in relation to streams, aspect, drainage area, and so on) to translate point-scale trace gas measurements to the landscape scale. The project builds upon prior and ongoing NSF-funded research on hydrologic controls on carbon dioxide flux in montane ecosystems and uses existing field infrastructure and technical resources to advantage.Nitrous oxide and methane are, like carbon dioxide, radiatively active trace gases that contribute significantly to global warming. It is known that the montane forested ecosystems of North America are a significant carbon sink. However, the net impact of montane forested ecosystems on atmospheric warming potential is unclear because the net fluxes of other trace gases are not known. This is, in part, because effective approaches to translate point trace gas flux measurements to whole landscapes have yet to be developed for such systems. The approach that will be developed and tested in this project has the potential to improve net greenhouse gas emission estimates for montane forested ecosystems at the landscape scale ? the spatial scale considered in policymaking regarding greenhouse gas emissions. In addition, this research project will provide land-air carbon dioxide, nitrous oxide and methane flux data at multiple space and time scales that will be useful to scientists interested in benchmarking models. Hands-on field training opportunities in hydrology and biogeochemistry will be provided for graduate and undergraduate students from Montana State University.