Effects of discharge level on the load of dissolved and particulate components of stream nitrogen and phosphorus from a small afforested watershed of Japanese cypress (Chamaecyparis obtusa)
Effects of discharge level on the load of dissolved and particulate components of stream nitrogen and phosphorus from a small afforested watershed of Japanese cypress (Chamaecyparis obtusa)
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DOI：
10.1007/s10310-006-0250-7
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发表时间：
2007-02
影响因子：
1.5
通讯作者：
J. Ide;O. Nagafuchi;M. Chiwa;A. Kume;K. Otsuki;S. Ogawa
中科院分区：
文献类型：
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作者：
J. Ide;O. Nagafuchi;M. Chiwa;A. Kume;K. Otsuki;S. Ogawa
在一个主要由日本柏树 (Chamaecyparis obtusa) 人工林覆盖的小山区流域中，对溪流中氮 (N) 和磷 (P) 的溶解成分和颗粒成分的行为进行了两年的测量。溶解的氮和磷的负荷与排放量具有一致的关系，而颗粒物氮和磷的负荷在给定的排放水平下变化最多两个数量级。大多数氮以溶解形式（DN）出口，而大多数磷以颗粒形式（PP）出口，这与农业流域的负荷相似。由于 DN 和 PP 的不同行为，总氮 (TN) 负荷的变化主要归因于排放量的变化，这与总磷 (TP) 负荷的变化不同。强降雨导致的高流量条件显示 PP 释放量明显高于预期。使用表示为流量函数的回归方程严重低估了高流量条件下的总磷负荷，该回归方程基于偏向低流量条件的每周采样数据。此外，由于颗粒物成分的不可预测的增加，回归方程低估了暴雨峰值流量期间的总氮负荷。我们的研究表明，无论化学物质如何，颗粒物成分比例决定了排放是否可以解释负荷变化。结果表明，根据土壤表面条件，多雨地区的人工林可以成为颗粒养分的扩散源。
The behavior of dissolved and particulate components of stream nitrogen (N) and phosphorus (P) were measured for 2 years in a small mountainous watershed covered primarily with a plantation forest of Japanese cypress (Chamaecyparis obtusa). The load of dissolved N and P bore a consistent relationship to discharge while the load of particulate N and P varied by up to two orders of magnitude at a given discharge level. Most N was exported in a dissolved form (DN) while most P was exported in a particulate form (PP), which bears similarity to loads from agricultural watersheds. Owing to the different behaviors of DN and PP, changes in the total nitrogen (TN) load were primarily attributed to variations in discharge unlike changes in the total phosphorus (TP) load. High flow conditions, resulting from heavy rainfall, displayed PP release significantly larger than expected. The TP load in high flow conditions was severely underestimated using a regression equation expressed as a function of discharge, which was based on the weekly sampling data biased toward low flow conditions. In addition, the TN load during peak discharges in heavy rain events was underestimated by the regression equation because of unpredictable increases in the particulate component. Our study shows that the particulate component ratio determines whether discharge can explain changes in load regardless of chemical species. The results suggest that plantation forests in rainy regions can be a diffuse source of particulate nutrients depending on soil surface conditions.