Linking land-use management and aquatic carbon : effects of forestry and peatland rewetting

Abstract

To manage the forested landscape in a sustainable way while maintaining or even improving its carbon (C) sequestration capacity is a key challenge in climate change mitigation strategies. An often neglected aspect in this context is how different management practices affect the export of terrestrial C via the aquatic pathway. In intensively managed boreal landscapes like Sweden, a dense network of man-made drainage ditches designed to promote forest growth receives high amounts of terrestrial C, with implications for C balance estimates and downstream water quality. This thesis presents field-based observations on the effects of clear-cutting, ditch cleaning (DC), and rewetting of drained wetlands on aquatic C of different forms. First, I show that clear-cutting can shift CO2 concentration dynamics in a boreal ditch from being mostly hydrologically driven to being mainly controlled by light- and temperature-dependent metabolic processes. Second, I explore the effect of DC on runoff chemistry by comparing cleaned and uncleaned ditches. Some results were consistent with earlier studies (higher pH), while others show divergent (similar total organic C (TOC)) or novel (higher nitrous oxide (N2O) and lower CO2) patterns in cleaned compared to uncleaned ditches. These patterns are suggested to stem from deeper flow paths and altered redox conditions after DC. Finally, I assess the effects of rewetting of drained wetlands on aquatic C at local and regional scales. Among the results, it was evident that rewetting increased the dissolved concentrations of organic and inorganic C (DOC and DIC), and methane (CH4) in runoff, which in turn caused enhanced lateral C exports. However, the effects were site-, C form- and season-specific and were influenced by e.g. presence of openwater areas, latitude and nutrient status. The thesis provides an important knowledge basis to be used when implementing the examined management practices, to ensure intended outcomes with minimal negative consequences on runoff C.

Keywords

Sweden; boreal; ditches; DOC; DIC; methane; ditch-cleaning; clear-cut

Published in

Acta Universitatis Agriculturae Sueciae
2024, number: 2024:86ISBN: 978-91-8046-377-5, eISBN: 978-91-8046-413-0Publisher: Swedish University of Agricultural Sciences

SLU Authors

• Zannella, Alberto

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Oceanography, Hydrology, Water Resources
Environmental Sciences


Publication identifier

DOI: https://doi.org/10.54612/a.4o4rtps8jn

Permanent link to this page (URI)

https://res.slu.se/id/publ/130481