BayCEER Workshop 2023

Allocation patterns of carbon and nitrogen between ectomycorrhizal associations of P. sylvestris and fungi with distinct decomposition strategies

Mycorrhizal fungi play a key role in carbon (C) and soil nutrient cycling. In addition to their effect on C input to the soil, they are thought to decompose soil organic matter (SOM) to extract nutrients such as nitrogen (N). Here, significant differences are expected between mycorrhizal association types or fungal species due to dissimilarities in the enzyme repertoire. Further, some species are thought to rely on the non-enzymatic decay via ‘Fenton chemistry’. Thus, we expect variations in litter decay by the ectomycorrhizal associations of Pinus sylvestris L. with Paxillus involutus and Hebeloma cylindrosporum, as these fungal species are phylogenetically distinct and exhibit different decay strategies.  We aim to test fungal species-dependent effects on (I) total litter decay and N transfer, (II) required plant C investment, and (III) the activity of underlying decomposition mechanisms. To address these questions, we have established a standardised microcosm set-up in bicompartmental Petri dishes, in which we combine plant seedlings with monoxenic cultures of selected fungi and add mesh bags with litters of different quality. The plant-fungus system grows under ¹³CO₂-depleted conditions and on ¹⁵N-enriched medium. Hence, the isotopic signature of the litter differs from other potential C and N sources, thus allows tracing the allocation patterns.

Background information on the topic and the detailed experimental approach will be presented.