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Content archived on 2024-05-29

Linking the genetic and functional diversity patterns of arbuscular mycorrhizal fungal communities in disturbed and undisturbed environments

Final Activity Report Summary - GENFUNDIV (Linking the genetic and functional diversity patterns of arbuscular mycorrhizal fungal communities in disturbed and undisturbed environments)

The overall goal of the project was to characterise taxonomically and functionally the diversity of arbuscular mycorrhizal (AM) fungi in a single location: a boreo-nemoral spruce forest with herb-rich understorey in Estonia. Arbuscular mycorrhiza is a symbiosis between plant roots and fungi from the phylum Glomeromycota. It is common in terrestrial ecosystems and is responsible for resource uptake by plants; fungi obtain carbon from the plants as their sole source of energy. The functional diversity of AM fungi affect the ecosystem function, including diversity and productivity. However, taxonomic and functional diversity of these fungi in natural ecosystems has been insufficiently described. Two mutually complementary approaches were taken in order to reach our aim. First, a survey of the fungal diversity in the study site was performed to describe the natural patterns of diversity. Second, experimentation with the fungi and plants from the study site was undertaken in the controlled conditions to determine the functional relationships between the symbiotic partners. This way, the observation and experimentation meet to provide deeper understanding of natural patterns and processes

The performed diversity survey of AM fungi provides unique information: from 12 host plant species, fungal DNA was amplified by polymerase chain reaction (PCR) from >200 samples, and > 2500 clones were sequenced. This approach resulted in ca 40 phylogenetically determined fungal taxa detected from the study site. This AM fungal richness is unique in temperate ecosystems and is larger than currently described from single locations in tropical forests. Our results show that herb-rich boreo-nemoral forests are important habitat for AM fungi. Our methodological approach (high number of plant species, high-throughput sequencing) possibly contributed to the observed unique richness.

In order to understand the determinants behind the observed fungal diversity, the vegetation, soil and light conditions were also described. Furthermore, the forests featured undisturbed and managed stands, which were both sampled several times per growth season and in a spatially intensive manner. We analysed the effect of these factors on the small-scale species richness of the AM fungi and on the fungal community composition. However, the fungal community patterns were not explainable by any of these, and there was no effect of forest management on fungal richness and community composition, indicating that moderate forest management can have no long term deteriorating effect on soil biodiversity.

The experimentation with the naturally co-occurring fungi and plants showed that the mutual effects of the symbiosis partners are diverse and complex. An experiment with plant species of different functional types and contrasting AM fungal assemblages from undisturbed forest, managed forest and arable field demonstrated differential effect of fungi on the coexisting plant species. This indicates that there is no single set of fungi which would be optimal for all plants; on the contrary, the complex interactions may contribute to the observed plant and fungal community patterns and dynamics in nature.

Further experimentation was performed with single fungal isolates from the managed and undisturbed stands in the studied forest and manipulated light conditions in order to test for the adaptation of fungi for local light availability. The light conditions in differently managed forest stands vary; less light would mean limited photosynthesis and thus smaller amount of carbon available for symbiotic fungi. Our experimental results showed that there was no single level of light availability that would be the best for the used fungi.

In conclusion, the boreo-nemoral forest study site in Estonia is unique in terms of described plant and fungal diversity and abiotic conditions. The mycorrhizal fungi isolated from the location and maintained in culture collection are an invaluable source for functional experimentation to advance the understanding of natural ecosystem functioning, and for inoculum development for ecosystem restoration or agricultural/horticultural use.