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Research article - Peer-reviewed, 2022

The role of terrestrial productivity and hydrology in regulating aquatic dissolved organic carbon concentrations in boreal catchments

Zhu, Xudan; Chen, Liang; Pumpanen, Jukka; Ojala, Anne; Zobitz, John; Zhou, Xuan; Laudon, Hjalmar; Palviainen, Marjo; Neitola, Kimmo; Berninger, Frank

Abstract

The past decades have witnessed an increase in dissolved organic carbon (DOC) concentrations in the catchments of the Northern Hemisphere. Increasing terrestrial productivity and changing hydrology may be reasons for the increases in DOC concentration. The aim of this study is to investigate the impacts of increased terrestrial productivity and changed hydrology following climate change on DOC concentrations. We tested and quantified the effects of gross primary production (GPP), ecosystem respiration (RE) and discharge on DOC concentrations in boreal catchments over 3 years. As catchment characteristics can regulate the extent of rising DOC concentrations caused by the regional or global environmental changes, we selected four catchments with different sizes (small, medium and large) and landscapes (forest, mire and forest-mire mixed). We applied multiple models: Wavelet coherence analysis detected the delay-effects of terrestrial productivity and discharge on aquatic DOC variations of boreal catchments; thereafter, the distributed-lag linear models quantified the contributions of each factor on DOC variations. Our results showed that the combined impacts of terrestrial productivity and discharge explained 62% of aquatic DOC variations on average across all sites, whereas discharge, gross primary production (GPP) and RE accounted for 26%, 22% and 3%, respectively. The impact of GPP and discharge on DOC changes was directly related to catchment size: GPP dominated DOC fluctuations in small catchments (<1 km(2)), whereas discharge controlled DOC variations in big catchments (>1 km(2)). The direction of the relation between GPP and discharge on DOC varied. Increasing RE always made a positive contribution to DOC concentration. This study reveals that climate change-induced terrestrial greening and shifting hydrology change the DOC export from terrestrial to aquatic ecosystems. The work improves our mechanistic understanding of surface water DOC regulation in boreal catchments and confirms the importance of DOC fluxes in regulating ecosystem C budgets.

Keywords

boreal catchments; catchment size; discharge; DOC; GPP; landscape; RE; terrestrial productivity

Published in

Global Change Biology
2022, volume: 28, number: 8, pages: 2764-2778
Publisher: WILEY

Authors' information

Zhu, Xudan
University of Eastern Finland
Chen, Liang
University of Eastern Finland
Pumpanen, Jukka
University of Eastern Finland
Ojala, Anne
Natural Resources Institute Finland (Luke)
Zobitz, John
Augsburg University
Zhou, Xuan
University of Eastern Finland
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Palviainen, Marjo
University of Helsinki
Neitola, Kimmo
University of Helsinki
Berninger, Frank
University of Eastern Finland

Sustainable Development Goals

SDG6 Clean water

UKÄ Subject classification

Ecology
Forest Science

Publication Identifiers

DOI: https://doi.org/10.1111/gcb.16094

URI (permanent link to this page)

https://res.slu.se/id/publ/116166