Effects of deep percolation on dissolved inorganic nitrogen exports from forested headwater catchments

• Published in: Journal of forest research Vol. 21; no. 2; pp. 57 - 66
• Main Authors: Iwasaki, Kenta, Katsuyama, Masanori, Tani, Makoto
• Format: Journal Article
• Language: English
• Published: Tokyo Taylor & Francis 01.04.2016; Springer Japan; Taylor & Francis Ltd
• Subjects: Bedrock infiltration; Biomedical and Life Sciences; Catchments; Deep percolation; Dissolved inorganic nitrogen; Drinking water; Ecosystems; Exports; Forestry; Forestry Management; Groundwater discharge; Life Sciences; Natural resource management; Nitrogen; Nitrogen budget; Original Article; Percolating water; Percolation; Plant Ecology; Plant Sciences; Precipitation; Runoff; Stream chemistry; Stream discharge; Stream flow; Stream water; Studies; Tree Biology; Turbulent flow; Water budget; Watersheds; Japan; Stream chemistry; Bedrock infiltration; Dissolved inorganic nitrogen; Nitrogen budget; Deep percolation
• ISSN: 1341-6979; 1610-7403
• DOI: 10.1007/s10310-015-0517-y

We examined the effects of deep percolation on dissolved inorganic nitrogen (DIN) exports from two adjacent weathered granite headwater catchments with different deep percolations of water in the Kiryu Experimental Watershed (KEW), Japan. The DIN output in streamflow was estimated from a regression equation between stream discharge and the DIN load, determined from both monthly sampling data and event-based sampling data. The range of deep percolation of DIN was estimated by multiplying observed DIN concentrations in bedrock groundwater by the deep percolation of water estimated from an annual water budget analysis. We found that the deep percolation of DIN corresponded to 34-76 % and −18 to 8 % of the total DIN output in catchments where the deep percolation of water was 37-45 % and −6 to 3 % of annual precipitation, respectively. This means that the deep percolation of DIN is not negligible when estimating the total output of DIN in the former catchment. Moreover, the fact that deep percolating water from upper catchments discharged into a lower catchment in KEW suggests that deep percolation of DIN affects downstream N budgets. Therefore, it is important to account for the deep percolation of DIN when evaluating N budgets in forested headwater catchments as well as downstream catchments.