The shifts in mycorrhizal symbionts within individual tree species under anthropogenic soil nutrient alteration - the effects on forest ecosystem processes

• Applicant: Rodica Pena, Ph.D.
• Subject Area: Forestry
• Term: from 2020 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 443040917

Temperate and boreal forest ecosystems are considered to be primarily nitrogen (N) limited. However, anthropogenic N deposition changes the stoichiometry of N relative to phosphorus (P) and gives rise to P co-limitation. The primary strategy of trees to cope with nutrient deficiency is to form symbioses with mycorrhizal fungi. The dominant mycorrhizal types, arbuscular mycorrhizas (AM) and ectomycorrhizas (EM) differ in carbon (C) and nutrient cycling mechanisms with divergent consequences on forest ecosystem processes (e.g., C sequestration). It is increasingly acknowledged, mainly through predictive models, that increasing of soil N:P ratio triggers the transition in forest composition from EM to AM trees dominance. This transition involves the decrease of soil C storages with a strong negative impact on ecosystem function. However, genera from major tree families (Fagaceae, Pinaceae, Salicaceae, Myrtaceae) are capable of forming both types of mycorrhizas in a dual symbiosis within the same individual species. The understanding of the mechanistic effects of dual mycorrhizas on ecosystem processes, as well as their response to anthropogenic soil nutrient change, is still in its infancy.The objective of this proposal is to investigate under the modified soil N:P ratio, the interactions of trees with soil fungi at a scale that enables us to understand and quantify the consequences of a shift in mycorrhizal type within a tree species on forest ecosystem processes. Specifically, I will 1) relate the changes in root-associated fungal communities and mycorrhizal type to soil N:P ratios in three distinct tree model systems, conifer - Douglas fir, broadleaf -Black poplar, and the P-sensitive Australian Jarrah, 2) describe the functional output of tree-soil fungi interactions by measuring the intensity and spatial distribution of soil enzymes by zymography, and 3) measure the effects of mycorrhizal type shift and/or changes in fungal functional communities within a tree species on tree productivity, leaf litter decomposition, and soil fungal biomass.The results of this research will contribute to developing specific strategies (e.g., species selection) of adaptive forest management that increase the ecosystem resilience to environmental change.

• DFG Programme: Research Fellowships
• International Connection: United Kingdom
• Host: Professor Dr. Mark Tibbett