Plant physiological responses to hydrologically mediated changes in nitrogen supply on a boreal forest floodplain: a mechanism explaining the discrepancy in nitrogen demand and supply

摘要: A discrepancy between plant demand and soil supply of nitrogen (N) has been observed in early successional stages riparian vegetation interior Alaska. We hypothesized that a hydrologically mediated N serves as mechanism to balance this apparent deficiency supply. To test hypothesis, we conducted tracer experiment measured the activity nitrate reductase (NRA) over summer on floodplain Tanana River Isotopic data showed river-/groundwater was an important source water hyporheic could be absorbed by species. Plant NRA generally increased growing season progressed, NO3−-N availability increased. Both Salix Rowlee Populus balsamifera L. used NO3−-N, timing relative river discharge chemistry concentrations, strongly suggest uptake is coupled fluvial dynamics. Moreover, physiological function helps explain mineralization productivity these ecosystems, demonstrates stands under significant hydrological control.