| Project/Area Number |
08680552
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Environmental dynamic analysis
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| Research Institution | Tokyo University of Agriculture & Technology |
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Principal Investigator |
YOH Muneoki Tokyo Univ.Agric.Tech., Assis.Prof., 農学部, 助手 (50260526)
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| Project Period (FY) |
1996 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1997: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1996: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | stream water / nitrate / nitrogen cycle / forest / nitrogen saturation / CN ratio / atmospheric deposition / temperature / 富栄養化 / 硝酸態窒素濃度 / 地域的変動メカニズム / 温度の影響 / 土壌C / N比 / 有機化 |
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| Research Abstract |
(1) Concentration of nitrate (NO_3) in stream waters were surveyed over 60 natural streams with forested catchments around central part of Japan. The results indicated that not a few streams contained considerable amounts of NO_3 more than 70 muM.Lower NO_3 concentrations were found in streams in higher altitudes that NO_3 levels were elevated along the course of air pollutant transportation.
(2) The studies of chemical properties of the watershed soils demonstrated that the C/N ratio increased in regions of colder climate and that the proportion of soil NO_3 to total nitrogen were small in higher C/N ratios.
(3) The results of laboratory incubation of soils showed that net NO_3 production was remarkable for soils with C/N ratios less than 20 ; for C/N ratio more than 20, the production of CO_2 was dominant relative to NO_3 production.
(4) The soil temperature was recorded for more than one year by loggers in four representative deistricts. The dairy average temperature differed by 6.0 ﾟC throughout a year along the stream NO_3 gradient of 30-fold.
(5) The above results suggests that stream water NO_3 could serve as a valuable parameter which give information on the nitrogen cycles by a catchment scale. Consequently, it is concluded that the obseved variation of stream NO_3 levels was associated with the entire cyclings of nitrogen in watershed even when atmospheric deposition of nitrogen may alter stream water chemistry.
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