Influence of environmental changes on the rooted area of forest trees: condition of mycorrhizas
Rationale
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Ectomycorrhizal birch seedling (Betula pendula - Paxillus involutus) grown on nutrient medium in a Petri dish.
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The fine roots of forest trees are the actual interface between the soil solution and plants. However, physiologically active fine roots are usually associated with mycorrhizal fungi, the so-called mycorrhizas. The trees profit from this interaction in two ways:
- Fungal hyphae increase the absorption area for the uptake of minerals by exploiting the soil solution in the finest soil-pores
- The colonization of the rootlets by fungal mycelia increases the tolerance against frost, drought, and pathogenic organisms.
Mycorrhizas themselves are organs of assimilation and accumulation of minerals and other elements (aluminum, heavy metals, radioisotopes). In exchange for carbohydrates, the fungal partner transports minerals and assimilation products to the plant. Increasing nitrogen and acid inputs into forest ecosystems alter the chemistry of the soil solution. Mycorrhizas react with structural and biochemical changes, but also with a decrease of the extramatrical mycelium. The changes potentially threaten the proper functioning of the mycorrhizas, with possible adverse consequences for tree vitality.
Project aims
The aim of the project is the evaluation of indicative parameters of fine roots or defined mycorrhizas in relation to environmental changes (increasing nitrogen inputs, soil acidification). These parameters should characterize the condition of the organs in relation to their functioning. Potential parameters are modifications to the structure, the element content, and the biochemistry of the fine roots and the mycorrhizas. In particular, the expression of genes responsible for the enzymes involved in assimilation and transport of mineral nutrients (e.g. enymes of the nitrogen assimilation) is being investigated.
Methods
- Field work
Sampling of fine roots in subalpine conifer forests, estimation of biomass, element content, starch content, and vitality. Sampling of mycorrhizas (Hebeloma, Cenococcum) and freezing in liquid nitrogen for analysis of the expression of certain indicative genes.
- Laboratory work
Performance of experiments in climatic chambers and greenhouses with conifer seedlings, non-inoculated or inoculated with mycorrhizal fungi, untreated or treated with various concentrations and forms of nitrogen. Analysis of mycorrhization, element contents, and comparison of the expression of induced and constitutive genes from plants or fungi using RT-PCR and specific primers.
Work plan
- Field work
Sampling of fine roots and mycorrhizas in subalpine conifer forests (Chironico / TI, Beatenberg / BE, National Park / GR), preparing the materials for the various analyses.
- Laboratory work
Experiments in climatic chambers and greenhouses, analyses of the plant and fungal material, verification of optimal RNA-extractions and RT-PCR- conditions, application of specific and degenerated primers for genes involved in the nitrogen metabolism of conifers and mycorrhizal fungi.
Participants
- Sabine Brodbeck
- Ivano Brunner
Contact
Further information
Related LTFER-projects are "Mapping, survey and analysis of soils on the LTFER plots (core project)", "Diversity of ectomycorrhizas", and "Occurrence and distribution of Armillaria spp. in Switzerland".
