Author:
Mari Moora

Doctoral defence: Maret Gerz “The distribution and role of mycorrhizal symbiosis in plant communities”

On 25 January at 10:15 Maret Gerz will defend her doctoral thesis “The distribution and role of mycorrhizal symbiosis in plant communities” for obtaining the degree of Doctor of Philosophy (in Plant Ecology and Ecophysiology).

Supervisors:
Prof. Mari Moora, University of Tartu
Assoc. Prof. Carlos Guillermo Bueno Gonzalez, University of Tartu

Opponent:
Prof. Richard Bardgett, University of Manchester (United Kingdom)

Summary
Mycorrhizal symbiosis between vascular plants and soil fungi is considered ubiquitous in terrestrial ecosystems and plays a key role in ecosystem processes. This doctoral thesis advances our understanding about the distribution of mycorrhizal symbiosis in vegetation at larger scales, its drivers and how it relates to plant coexistence and diversity. At regional scale, we show quantitatively that the forests in Estonia are more mycorrhizal but less arbuscular mycorrhizal than grasslands and vice versa. These distribution patterns were driven by edaphic factors, such as soil fertility, pH and moisture. At the continental scale, we revealed the latitudinal distribution patterns of plants with different mycorrhizal traits: arbuscular mycorrhizal plants prevailed across Europe, although their share decreased in the north, while minor but opposite trends were observed for ecto- and ericoid mycorrhizal plants. Northern areas in Europe were characterized by increased share of non-mycorrhizal and facultatively mycorrhizal plants. The mycorrhizal distribution at the continental scale was driven both by soil and climatic factors. Our results also suggest that arbuscular mycorrhization in Estonian forests is associated with higher plant richness. Mycorrhizal symbiosis could potentially affect plant diversity by reducing resource competition between plant species, i.e., by promoting plant niche partitioning. For the first time, we show that plants with different mycorrhizal characteristics indeed show evidence of niche differentiation. Also, mycorrhizal associations could be influenced by increasing human pressure on ecosystems. The analysis of the Dutch vegetation showed that mycorrhization of plant communities is affected by anthropogenic influence, but the effect depends on the type of human impact and the dominant mycorrhizal type. However, the mycorrhization of forests and heathlands were most affected, potentially also having subsequent effects on nutrient cycling.

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