Nitrogen release in decomposition of boreal mor and peat as affected by enchytraeid worms

• Published in: Boreal environment research 2013, Vol.18 (3-4), p.181-194
• Main Authors: LAPPALAINEN, Mari, KUKKONEN, Jussi V. K, PIIRAINEN, Sirpa, SARJALA, Tytti, SETÄLÄ, Heikki, KOIVUSALO, Harri, FINER, Leena, LAUREN, Ari
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General aspects; Marine and continental quaternary; Surficial geology; Synecology
• ISSN: 1239-6095; 1797-2469

Mor, slightly decomposed peat and highly decomposed peat, two soil types of each, were incubated for 154 days in the laboratory at +15 °C with and without enchytraeid worms, which functionally are the most influential faunal group in boreal forests. We quantified the release rates of organic and inorganic nitrogen (N) in dissolved and extractable forms from decomposing organic matter and explored the effects of enchytraeid worms on the release rates. About 80% of the dissolved N was released in the form of NH4+-N, except in mor without worms and in slightly decomposed peat with and without worms, where the net release from soil solution was in the form of dissolved organic N (DON). The majority of DON was in the high molecular weight fraction. In the presence of worms, the mineralization rate of N was highest in mor and in the absence of worms in highly decomposed peat. The large initial DON pool may explain the high mineralization rate in highly decomposed peat. The changes in the soil-solution N pool were small compared to the changes in extractable N pool which emphasizes the importance of the adsorbed N in soil N dynamics. Because N release through decomposition is the major component of N balance in forested catchments, the results of the study can be used for improving models of catchment scale N dynamics.