University of Oulu

de Wit, HA, Lepistö, A, Marttila, H, et al. Land‐use dominates climate controls on nitrogen and phosphorus export from managed and natural Nordic headwater catchments. Hydrological Processes. 2020; 34: 4831– 4850.

Land‐use dominates climate controls on nitrogen and phosphorus export from managed and natural Nordic headwater catchments

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Author: de Wit, Heleen A.1,2,3; Lepistö, Ahti4; Marttila, Hannu5;
Organizations: 1Norwegian Institute for Water Research (NIVA), Oslo, Norway
2Department of Biological Sciences, University of Oslo, Oslo, Norway
3Centre for Biogeochemistry in the Anthropocene, University of Oslo, Oslo, Norway
4Finnish Environment Institute SYKE, Helsinki, Finland
5Water, Energy and Environmental Engineering Research Unit, University of Oulu, Oulu, Finland
6The Norwegian Institute of Bioeconomy Research (NIBIO), Ås, Norway
7Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway
8Department of Bioscience, Aarhus University, Silkeborg, Denmark
9Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden
10Department of Soil and Environment, Swedish University of Agricultural Sciences, Uppsala, Sweden
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 6.8 MB)
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Language: English
Published: John Wiley & Sons, 2020
Publish Date: 2021-01-21


Agricultural, forestry‐impacted and natural catchments are all vectors of nutrient loading in the Nordic countries. Here, we present concentrations and fluxes of total nitrogen (totN) and phosphorus (totP) from 69 Nordic headwater catchments (Denmark: 12, Finland:18, Norway:17, Sweden:22) between 2000 and 2018. Catchments span the range of Nordic climatic and environmental conditions and include natural sites and sites impacted by agricultural and forest management. Concentrations and fluxes of totN and totP were highest in agricultural catchments, intermediate in forestry‐impacted and lowest in natural catchments, and were positively related %agricultural land cover and summer temperature. Summer temperature may be a proxy for terrestrial productivity, while %agricultural land cover might be a proxy for catchment nutrient inputs. A regional trend analysis showed significant declines in N concentrations and export across agricultural (−15 μg totN L⁻¹ year⁻¹) and natural (−0.4 μg NO₃‐N L⁻¹ year⁻¹) catchments, but individual sites displayed few long‐term trends in concentrations (totN: 22%, totP: 25%) or export (totN: 6%, totP: 9%). Forestry‐impacted sites had a significant decline in totP (−0.1 μg P L⁻¹ year⁻¹). A small but significant increase in totP fluxes (+0.4 kg P km⁻² year⁻¹) from agricultural catchments was found, and countries showed contrasting patterns. Trends in annual concentrations and fluxes of totP and totN could not be explained in a straightforward way by changes in runoff or climate. Explanations for the totN decline include national mitigation measures in agriculture international policy to reduced air pollution and, possibly, large‐scale increases in forest growth. Mitigation to reduce phosphorus appears to be more challenging than for nitrogen. If the green shift entails intensification of agricultural and forest production, new challenges for protection of water quality will emerge possible exacerbated by climate change. Further analysis of headwater totN and totP export should include seasonal trends, aquatic nutrient species and a focus on catchment nutrient inputs.

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Series: Hydrological processes
ISSN: 0885-6087
ISSN-E: 1099-1085
ISSN-L: 0885-6087
Volume: 34
Issue: 25
Pages: 4831 - 4850
DOI: 10.1002/hyp.13939
Type of Publication: A1 Journal article – refereed
Field of Science: 1172 Environmental sciences
218 Environmental engineering
Funding: NordForsk, Grant/Award Number: 82263.
Copyright information: © 2020 The Authors. Hydrological Processes published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.