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)

• DOI: 10.1007/s10310-006-0250-7
• Publication Date: 2007-02-02T22:03:28Z
• Authors: Jun'ichiro Ide; Osamu Nagafuchi; Masaaki Chiwa; Atsushi Kume; Kyoichi Otsuki; Shigeru Ogawa
• Keywords: Chamaecyparis; Cypress; Discharge

The behavior of dissolved and particulate components stream nitrogen (N) phosphorus (P) were measured for 2 years in a small mountainous watershed covered primarily with plantation forest Japanese cypress (Chamaecyparis obtusa). load N P bore consistent relationship to discharge while the varied by up two orders magnitude at given level. Most was exported form (DN) most (PP), which bears similarity loads from agricultural watersheds. Owing different behaviors DN PP, changes total (TN) attributed variations unlike (TP) load. High flow conditions, resulting heavy rainfall, displayed PP release significantly larger than expected. TP high conditions severely underestimated using regression equation expressed as function discharge, based on weekly sampling data biased toward low conditions. In addition, TN during peak discharges rain events because unpredictable increases component. Our study shows that component ratio determines whether can explain regardless chemical species. results suggest forests rainy regions be diffuse source nutrients depending soil surface