University of Oulu

Paavo Ojanen, Timo Penttilä, Anne Tolvanen, Juha-Pekka Hotanen, Miia Saarimaa, Hannu Nousiainen, Kari Minkkinen, Long-term effect of fertilization on the greenhouse gas exchange of low-productive peatland forests, Forest Ecology and Management, Volume 432, 2019, Pages 786-798, ISSN 0378-1127,

Long-term effect of fertilization on the greenhouse gas exchange of low-productive peatland forests

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Author: Ojanen, Paavo1,2; Penttilä, Timo2; Tolvanen, Anne3,4;
Organizations: 1University of Helsinki, Department of Forest Sciences, P.O. Box 27, FI-00014 Helsinki, Finland
2Natural Resources Institute Finland, Latokartanonkaari 9, FI-00790 Helsinki, Finland
3Natural Resources Institute Finland, P.O. Box 413, FI-90014 University of Oulu, Finland
4University of Oulu, Department of Genetics and Ecology, FI-90014 University of Oulu, Finland
5Natural Resources Institute Finland, Yliopistokatu 6, FI-80100 Joensuu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.1 MB)
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Language: English
Published: Elsevier, 2019
Publish Date: 2019-07-02


Drainage of peatlands for forestry often leads to carbon dioxide (CO2) net emission from soil due to loss of peat. This emission can be compensated for by the increased tree growth. Hovewer, many drained peatlands have low tree growth due to nutrient limitations. Tree growth at these peatlands can be effectively increased by fertilization, but fertilization has been also found to increase decomposition rates.

We studied the long-term effect of fertilization of low-productive forestry-drained peatlands on the complete ecosystem greenhouse gas exchange, including both soil and tree component, and accounting for CO2, methane and nitrous oxide. Five N-rich study sites (flark fens and a rich fen) and one N-poor ombrotrophic site were established. Fertilization had started at the study sites 16–67 years before our measurements.

Fertilization considerably increased tree stand CO2 sink (+248–1013 g CO2 m−2 year−1). Decomposition increased on average by 45% (+431 g CO2 m−2 year−1) and litter production by 38% (+360 g CO2 m−2 year−1). Thus, on average 84% of the increased decomposition could be attributed to increased litter production and 16% to increased soil CO2 net emission due to increased loss of peat. Soil CO2 net emission correlated positively with water table depth and top soil N concentration.

Fertilization increased soil CO2 net emission at the drained flark fens on average by 187 g CO2 m−2 year−1. At the rich fen, net emission decreased. The N-poor bog exhibited soil CO2 sink both with and without fertilization. Effects on methane and nitrous oxide emissions were small at most sites.

The increase in tree stand CO2 sink was higher than the increase in soil CO2 net emission, indicating that fertilization has a climate cooling effect in the decadal time scale. Yet, as the fertilized plots at N-rich sites exhibited soil CO2 source or zero balance, continuation of fertilization-based forestry over several rotations would lead to progressive loss of ecosystem C. At the N-poor bog, fertilization-based forestry may have a climate-cooling effect also in the centennial time scale.

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Series: Forest ecology and management
ISSN: 0378-1127
ISSN-E: 1872-7042
ISSN-L: 0378-1127
Volume: 432
Pages: 786 - 798
DOI: 10.1016/j.foreco.2018.10.015
Type of Publication: A1 Journal article – refereed
Field of Science: 4112 Forestry
Funding: This study was funded principally by LIFE+ (LIFEPeatLandUse, LIFE12ENV/FI/150 Action B3). The work of Paavo Ojanen has also been funded by Kone Foundation (Koneen Säätiö).
Copyright information: © 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (