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  • 1.
    Haas, Julia Christa
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Abiotic stress and plant-microbe interactions in Norway spruce2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Norway spruce (Picea abies) is a dominant tree species in boreal forests with extensive ecological and economic value. Climate change is threatening these ecosystems, with rising temperatures impacting cold hardening and increasing drought stress in regions experiencing lower precipitation. Increasing atmospheric CO2 concentrations and nitrogen deposition can, in contrast, partially offset such negative effects by improving tree growth and carbon uptake. Similar to aboveground carbon fixation, carbon sequestration in boreal soils is important. Bacteria and fungi mineralize organic matter and, by making nutrients available for plants, are important for tree health. The ability of Norway spruce and the associated microbiota to adapt to climate change is of fundamental importance for ecosystem functioning and is the focus of this thesis.

    Norway spruce seedlings were subjected to cold or drought stress and the transcriptional response compared to known mechanisms in the model plant Arabidopsis thaliana. Analyses revealed that while there was overlap in the stress responses between species, including increased osmotic and oxidative stress tolerance, the majority of differentially expressed genes were stress-responsive only in Norway spruce. Importantly, transcription factors of the abscisic acid dependent and independent pathways were not differentially expressed or were missing homolog sequences in Norway spruce, indicating that different regulatory pathways are active in Norway spruce and suggesting that stress response has evolved differently in the species. Furthermore, differential gene expression in roots differed extensively from that of needles in response to stress and highlighted the need for separate profiling in above- and belowground tissues.

    In another study at the Flakaliden research site in northern Sweden, the effects of long-term nutrient addition on the microbiota associated with mature Norway spruce were tested. In agreement with earlier findings, nutrient addition improved tree growth and phylogenetic marker gene analysis on DNA of fungi and bacteria provided new insights into associated changes in plant-microbe interactions. Microbial diversity increased over time and compositional changes in nitrophilic community members indicated changes in carbon and nitrogen cycling at the plant-microbe interface, which has implications for carbon storage in boreal forest soils in the future. Follow-up RNA-based techniques largely confirmed community members from marker gene analysis.

    In summary, understanding of both the Norway spruce-specific responses to abiotic stress and the ability of the associated microbiota to cope with the environmental changes are essential for future productivity, survival and distribution of Norway spruce forests. Sustainability will depend on tree vitality and a more holistic understanding of tree-microbe interactions is required to model future sustainability.

  • 2.
    Haas, Julia Christa
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Street, Nathaniel R.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Sjödin, Andreas
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Division of CBRN Security and Defence, FOI–Swedish Defence Research Agency, Umeå, Sweden.
    Lee, Natuschka M.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Högberg, Mona N.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
    Näsholm, Torgny
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden; Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, SLU, Umeå, Sweden.
    Hurry, Vaughan
    Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, SLU, Umeå, Sweden.
    Microbial community response to growing season and plant nutrient optimisation in a boreal Norway spruce forest2018In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 125, p. 197-209Article in journal (Refereed)
    Abstract [en]

    Interactions between Norway spruce trees and bacteria and fungi in nutrient limited boreal forests can be beneficial for tree growth and fitness. Tree-level effects of anthropogenic nutrient addition have been well studied, however understanding of the long-term effects on the associated microbiota is limited. Here, we report on the sensitivity of microbial community composition to the growing season and nutrient additions. Highthroughput sequencing of the bacterial 16S rRNA gene and fungal ITS1 region was used to characterise changes in the microbial community after application of a complete mineral nutrient mixture for five and 25 years. The experiment was conducted using the Flakaliden forest research site in northern boreal Sweden and included naturally low nutrient control plots. Needle and fine root samples of Norway spruce were sampled in addition to bulk soil during one growing season to provide comprehensive insight into phyllosphere and belowground microbiota community changes. The phyllosphere microbiota was compositionally distinct from the belowground communities and phyllosphere diversity increased significantly over the growing season but was not influenced by the improved nutrient status of the trees. In both root and soil samples, alpha diversity of fungal, in particular ectomycorrhizal fungi (EMF), and bacterial communities increased after long-term nutrient optimisation, and with increasing years of treatment the composition of the fungal and bacterial communities changed toward a community with a higher relative abundance of nitrophilic EMF and bacterial species but did not cause complete loss of nitrophobic species from the ecosystem. From this, we conclude that 25 years of continuous nutrient addition to a boreal spruce stand increased phylotype richness and diversity of the microbiota in the soil, and at the root-soil interface, suggesting that long-term anthropogenic nutrient inputs can have positive effects on belowground biodiversity that may enhance ecosystem robustness. Future studies are needed to assess the impact of these changes to the microbiota on ecosystem carbon storage and nitrogen cycling in boreal forests.

  • 3.
    Sundström, Görel
    et al.
    Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
    Schneider, Andreas N.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Richau, Kerstin
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Haas, Julia Christa
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Delhomme, Nicolas
    Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
    Sjödin, Andreas
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Division of CBRN Security and Defence, FOI-Swedish Defence Agency.
    Hurry, Vaughan
    Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
    Grabherr, Manfred
    Department of Medical Biochemistry and Microbiology, Uppsala University, Sweden.
    Street, Nathaniel R.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Reproducibility and biological information of tree-associated metacommunities using RNA Sequencing and DNA amplicon profilingManuscript (preprint) (Other academic)
  • 4.
    Vergara, Alexander
    et al.
    Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
    Haas, Julia Christa
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Stachula, Paulina
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Street, Nathaniel Robert
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Hurry, Vaughan
    Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
    Norway spruce deploys canonical and delayed cold acclimation responses in a tissue-specific mannerManuscript (preprint) (Other academic)
1 - 4 of 4
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