The shifts in mycorrhizal symbionts within individual tree species under anthropogenic soil nutrient alteration - the effects on forest ecosystem processes
Final Report Abstract
Forests in temperate and boreal regions typically exhibit limited nitrogen (N) availability, leading trees to form ectomycorrhizal (EM) symbiosis, enhancing N acquisition. Recent increases in anthropogenic N deposition, however, are altering this dynamic. This study aimed to understand how changes in soil N:P ratios affect tree-fungal associations, particularly in the context of mycorrhizal symbiosis. It focused on three hypotheses: the primary role of soil N:P ratio in driving changes in root-associated fungal communities, the relationship between rhizosphere enzymatic activities and fungal community composition, and the effect of mycorrhizal type shifts on ecosystem processes (i.e., tree productivity, leaf litter decomposition, soil carbon storage). Contrary to the initial hypothesis, variations in soil N:P ratio did not significantly alter the composition of root-associated and rhizosphere fungal communities. This challenges the prevailing view that EM fungi are favoured in low N:P environments, and high N:P ratios lead to the dominance of arbuscular mycorrhizal and other endophytic fungi. Enzymatic activities in the rhizosphere were only marginally influenced by the presence of fungal symbionts and the resource availability of the surrounding soil. However, a higher enzyme N:P ratio was observed, suggesting a greater N requirement in the rhizosphere of EM plants compared to other treatments. This inference was further substantiated by findings from a 15N tracer study, which revealed the highest amino acid uptake per root tip occurring at the lowest soil N availability. Overall, the project concludes that in the short term, the increases in the N:P ratio, akin to anthropogenic inputs, do not significantly impact the plant-soil system as expected. Contrary to what was hypothesised, nutrient imbalances had a less pronounced effect on root-associated fungal symbionts and their ecosystem roles. The findings hold substantial implications for forest management and ecological conservation, especially in understanding nutrient dynamics for tree seedlings in reforestation efforts. Future research should explore long-term impacts of altered N:P ratios and expand to different forest types and climates. A particularly noteworthy discovery was the dominance of Archaeorhizomyces in young pine rootassociated fungal communities, warranting further study into its functional role and potential in forestry practices. However, the current results are not yet commercially exploitable, indicating the need for continued research and exploration.
Publications
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Root-associated fungal communities - the key linkages between plants and soil. Understanding their structure and functioning to predict the impacts of change. Habilitation Thesis, Georg-August-Universität Göttingen
Pena R.
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Contrasting distribution of enzyme activities in the rhizosphere of European beech and Norway spruce. Frontiers in Plant Science, 13.
Song, Bin; Razavi, Bahar S. & Pena, Rodica
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An improved method for extraction of soil fungal mycelium. MethodsX, 11, 102477.
Awad, Abdallah & Pena, Rodica
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Mycorrhizal C/N ratio determines plant-derived carbon and nitrogen allocation to symbiosis. Communications Biology, 6(1).
Pena, Rodica; Bluhm, Sarah L.; Ammerschubert, Silke; Agüi-Gonzalez, Paola; Rizzoli, Silvio O.; Scheu, Stefan & Polle, Andrea
