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Quantifying the effects of clear-cutting and strip-cutting on nitrate dynamics in a forested watershed using triple oxygen isotopes as tracers

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Title: Quantifying the effects of clear-cutting and strip-cutting on nitrate dynamics in a forested watershed using triple oxygen isotopes as tracers
Authors: Tsunogai, U. Browse this author
Komatsu, D. D. Browse this author
Ohyama, T. Browse this author
Suzuki, A. Browse this author
Nakagawa, F. Browse this author
Noguchi, I. Browse this author
Takagi, K. Browse this author →KAKEN DB
Nomura, M. Browse this author
Fukuzawa, K. Browse this author →KAKEN DB
Shibata, H. Browse this author →KAKEN DB
Issue Date: 7-Jan-2015
Publisher: Copernicus Gesellschaft
Journal Title: Biogeosciences
Volume: 11
Issue: 19
Start Page: 5411
End Page: 5424
Publisher DOI: 10.5194/bg-11-5411-2014
Abstract: Temporal variations in the stable isotopic compositions of nitrate dissolved in stream water eluted from a cool-temperate forested watershed (8 ha) were measured to quantify the biogeochemical effects of clear-cutting of trees and subsequent strip-cutting of the understory vegetation, dwarf bamboo (Sasa senanensis), with special emphasis on changes in the fate of atmospheric nitrate that had been deposited onto the watershed based on Delta O-17 values of nitrate. A significant increase in stream nitrate concentration to 15 mu mol L-1 in spring of 2004 was correlated with a significant increase in the Delta O-17 values of nitrate. Additionally, the high Delta O-17 values of +14.3 parts per thousand suggest that the direct drainage of atmospheric nitrate accounted for more than 50% of total nitrate exported from the forested watershed peaking in spring. Similar increases in both concentrations and Delta O-17 values were also found in spring of 2005. Conversely, low Delta O-17 values less than +1.5% were observed in other seasons, regardless of increases in stream nitrate concentration, indicating that the majority of nitrate exported from the forested watershed during seasons other than spring was remineralized nitrate: those retained in the forested ecosystem as either organic N or ammonium and then been converted to nitrate via microbial nitrification. When compared with the values prior to strip-cutting, the annual export of atmospheric nitrate and remineralized nitrate increased more than 16-fold and fourfold, respectively, in 2004, and more than 13-fold and fivefold, respectively, in 2005. The understory vegetation (Sasa) was particularly important to enhancing biological consumption of atmospheric nitrate.
Rights: http://creativecommons.org/licenses/by/3.0/
Type: article
URI: http://hdl.handle.net/2115/57667
Appears in Collections:北方生物圏フィールド科学センター (Field Science Center for Northern Biosphere) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 柴田 英昭

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