Importance of frequent storm flow data for evaluating changes in stream water chemistry following clear-cutting in Japanese headwater catchments

作者：Oda Tomoki^*; Ohte Nobuhito; Suzuki Masakazu

来源：Forest Ecology and Management, 2011, 262(7): 1305-1317.

DOI：10.1016/j.foreco.2011.06.032

• Streamwater chemistry
• Forest
• Clear-cutting

This study investigated the changes in stream water chemistry during low flow and storm flow following clear-cutting in a paired forest catchments. Regular grab samples, obtained mainly during low flow. showed that the Cl- concentration in stream water decreased, the NO3- concentration increased, and the Na+, SO42-, K+, Mg2+, and Ca2+ concentrations did not change significantly after clear-cutting. Highly frequent samplings revealed that solute concentrations at high flow changed to a larger degree after cutting than those at low flow. The NO3- concentration at high flow changed earlier and to a greater degree than that at low flow. In addition, Na+, k(+), and Ca2+ also increased at high flow just after clear-cutting, in association with NO3- flushing. The mean annual NO3- export after clear-cutting, as estimated by the highly frequent samplings including concentrations during storm flow, was more than 60 kg ha(-1) and 1.5-fold higher than that calculated by only weekly sampling data. The largest difference was found 8 months after clear-cutting, when the methods differed by 40 kg ha(-1) yr(-1) and the estimate by the regular measurements with high-frequency sampling data was three-fold higher than that with the weekly regular sampling. These results show that high-frequency observation following forest cutting is important for accurate estimation of output fluxes.