Abstract
Great concern has been expressed in several European countries over dramatic declines in ectomycorrhizal (ECM) fungi resulting from the deposition of pollutant nitrogen (N) onto forest ecosystems. Similar reductions in diversity are also frequently observed after the addition of nitrogen fertilizers to increase wood production in boreal forests. However, some ECM fungi respond positively to nitrogen additions. By comparing these species with those that are severely negatively affected, it should be possible to determine which characteristics of ECM fungi make them sensitive to fertilisation. This project will investigate the mechanisms behind the observed changes in ECM diversity following fertilisation. The project is divided into sets of field and lab experiments designed to separate direct effects of fertilization upon the fungi and indirect effects mediated through the tree response to fertilisation. Potential direct toxicity effects of fertilisers will be examined and plant sanctioning against inefficient ECM fungi will be investigated. Identifying why ECM species are particularly sensitive to nitrogen may make it possible to suggest ways of balancing optimal production gains while minimising negative impacts upon ECM fungal diversity through altering fertilizer dosage, composition and timing of application.
Sweden