Arbuscular Mycorrhiza, Resource Availability and Belowground Interactions between Plants and Soil Microbes

Pietikäinen, Anne Arbuscular mycorrhiza, resource availability and belowground interactions between plants and soil microbes Jyväskylä: University of Jyväskylä, 2009, 38 p. (Jyväskylä Studies in Biological and Environmental Science ISSN 1456-9701; 200) ISBN 978-951-39-3555-9 (PDF), 978-951-39-3514-6 (nid.) Yhteenveto: Arbuskelimykorritsa, resurssien saatavuus ja maanalaiset kasvien ja mikrobien väliset vuorovaikutukset Diss. Most vascular plants house the Glomeromycotan fungi that form arbuscular mycorrhizal (AM) symbioses in their roots. This symbiosis is usually considered mutualistic. The AM fungus relies on the carbon provided by its plant host and in return the AM fungus can improve plant nutrients and water acquisition and provide protection from pathogens. By affecting the plant growth and resource allocation AM fungi may affect the interactions between plants, the plant community composition and the soil microbial community dependent on the plant derived carbon. I studied the interactions between plants and soil microbial community focusing on the symbiotic relationship between plants and arbuscular mycorrhizal fungi in low arctic meadow ecosystem. I found that changes in resource availability caused by defoliation and fertilization did not have significant effect on functioning of AM symbiosis on the basis of the AM fungal colonization rate in plant roots in low arctic meadow. It seems that other factors than resource availability are more important determining the AM fungal colonization rate in natural conditions. I found no evidence of mycorrhiza mediated facilitative interactions between seedlings and adult plants and the results of this thesis emphasize the importance of below-ground competition in seedling establishment. Furthermore, I showed that defoliation of the neighboring adult plant may improve seedling establishment by decreasing the competition for mycorrhiza mediated resources. In the low arctic meadow, the AM fungal diversity was not affected by short term changes in plant community composition. Functional AM fungal and saprophytic microbial community necessary for successful seedling establishment persisted in the soil for two years without vegetation cover. In general, the functioning AM symbiosis in low arctic meadow seems not to be markedly different from what is known about AM symbiosis in other ecosystems.