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Geaographical gradient of nitrate concentration in forest stream waters : A proof of ecological mechanism.

森林溪流水域硝酸盐浓度的地理梯度：生态机制的证明。

基本信息

批准号：
08680552
负责人：
YOH Muneoki
金额：
$ 1.41万
依托单位：
Tokyo University of Agriculture & Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

(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.

(1)对日本中部地区有森林流域的60多条天然溪流进行了溪流水中硝酸盐(NO_3)浓度的调查。结果表明,不少溪流中NO_3含量超过70μM。海拔较高的溪流NO_3浓度较低,空气污染物输送过程中NO_3浓度升高。(2)流域土壤化学性质研究表明,气候寒冷地区C/N比升高,土壤NO_3占总氮的比例较小。 (3)土壤实验室培养结果表明,C/N小于20的土壤NO_3净产生量显着;当C/N大于20时,CO_2的产生相对于NO_3的产生占主导地位。(4)采伐者对四个代表性地区的土壤温度进行了一年以上的记录。沿溪流NO_3梯度30倍，奶牛场全年平均温度相差6.0℃。(5)上述结果表明，溪流水NO_3可以作为一个有价值的参数，提供流域尺度的氮循环信息。因此，得出的结论是，即使大气中氮的沉降可能改变河流水的化学性质，所观察到的河流NO_3水平的变化也与流域中氮的整个循环有关。