open access

https://hdl.handle.net/2115/83153

Vertical Changes in the Flux of Atmospheric Nitrate From a Forest Canopy to the Surface Soil Based on Delta O-17 Values

英語

nitrogen deposition

2021-04

American Geophysical Union

Journal of geophysical research biogeosciences

126(4)

e2020JG005876

To better understand the factors that control N retention and N export in forested watersheds, it is necessary to understand the relationships among atmospheric nitrogen (N) deposition, internal N cycling within plant-soil systems, and N leaching. The relative contributions of atmospheric nitrate (NO3atm-) and remineralized nitrate produced by microbial nitrification to total nitrate (NO3-) in stream water have been investigated in many studies. However, the dynamics of these two types of NO3- from the forest canopy to the soil are not well understood. Therefore, we determined the changes in the NO3- flux and the O-17 excess (Delta O-17) of NO3-, a robust tracer of NO3atm-, from bulk deposition to the soil water beneath oak and spruce trees as well as dwarf bamboo-dominated canopy gaps in a natural coniferous-broadleaved mixed forest in northern Japan. The Delta O-17 values in NO3- dramatically decreased after passing through the forest floor, indicating that the dominant source of NO3- leaching is nitrification in the forest floor. In contrast, a large decrease in NO3atm- flux was observed between bulk deposition and throughfall, especially for oak and spruce, suggesting that the forest canopy is an important sink for deposited NO3atm-. The retention of NO3atm- by the canopy was higher for oak (86.3 +/- 10.1%) and spruce (87.7 +/- 8.8%) than for Sasa in the canopy gap (49.9 +/- 26.6%). Our study demonstrated that the Delta O-17 value of NO3- is a promising tool for quantifying the atmospheric nitrate dynamics in complex forest N cycling.

学術雑誌論文

Version of Record

2169-8953