Bizjak-Johansson, Tinkara
- Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences
Abstract
Forest microbiomes are integral parts of the forest ecosystem as they are involved in soil health, tree growth, plant resilience and nitrogen and carbon cycles. However, forest microbiomes are under-researched compared to microbiomes in agriculturally important environments. Therefore, the main aim of this thesis was to describe and analyse the fungal and bacterial microbiomes connected to Norway spruce and Scots pine growing in the Fennoscandian boreal forest and investigate the effect of nitrogen addition on these microbiomes. Additionally, the thesis assessed two potentially more sustainable alternatives to inorganic nitrogen fertilization. The results showed the microbiome compositions of bulk soil, humus, root and needle conifer samples, highlighted distinct microbiomes between bulk soil and needles and identified 15 culturable nitrogen-fixing bacteria isolated from Scots pine needles. The results further showed that increased nitrogen addition led to decreased fungal and bacterial abundance, changes in fungal microbiome composition and differences in the activity of several extracellular enzymes in humus. However, interestingly, nitrogen addition did not affect the activity of nitrogen-fixing bacteria inside Scots pine needles. The greenhouse study showed that controlled-release organic nitrogenbased nutrition was able to promote plant growth similar to inorganic nitrogen-based fertilizers but with lower nitrate leaching from the growth medium. Further, bacteria isolated from Scots pine needles showed plant growth-promoting properties in in vitro experiments but did not promote higher plant biomass of four different inoculated crop species in in vivo greenhouse study. In summary, the thesis offered a deeper look into diverse Fennoscandian boreal forest microbiomes and analysed the effects of inorganic nitrogen addition on both the presence and the activity of these microbiomes. Furthermore, the thesis highlighted the potential and challenges of possible sustainable alternatives to inorganic nitrogen fertilization.
Keywords
bacteria; boreal forest; fungi; inorganic and organic nitrogen; microbiome; nitrogen addition; nitrogen fixation; Norway spruce; plant growth-promoting bacteria; Scots pine
Published in
Acta Universitatis Agriculturae Sueciae
2025, number: 2025:30
Publisher: Swedish University of Agricultural Sciences
SLU Authors
UKÄ Subject classification
Forest Science
Microbiology
Molecular Biology
Publication identifier
- DOI: https://doi.org/10.54612/a.6dook1318f
- ISBN: 978-91-8046-465-9
- eISBN: 978-91-8046-515-1
Permanent link to this page (URI)
https://res.slu.se/id/publ/132970