Mycorrhizal associations of trees have different indirect effects on organic matter decomposition

Abstract

1. Organic matter decomposition is the main process by which carbon (C) is lost from terrestrialecosystems, and mycorrhizal associations of plants (i.e. arbuscular mycorrhizas (AM) and ectomycorrhizas(ECM)) may have different indirect effects on this loss pathway. AM and ECM plants differin the soil decomposers they promote and the quality of litter they produce, which may result indifferent patterns of organic matter decomposition, and hence, soil C loss.2. To determine how mycorrhizal associations indirectly affect decomposer activity, we collectedsoils and litters from four AM and four ECM tree species from a mixed-deciduous temperate forestfor a field and laboratory study. We first characterized in situ patterns in soil chemistry and soilmicrobial biomass among these eight tree species. We then conducted a microcosm experiment withmineral soils, leaf litter and fine roots originating from these tree species, where we reciprocallycrossed litters and soils, and quantified the rate of heterotrophic respiration over a 140-day laboratoryincubation.3. In natural forest conditions, AM tree soils contained lower total C and microbial biomass C:Nrelative to ECM tree soils. In our microcosm experiment, AM soils supported greater heterotrophicrespiration than did ECM soils. The addition of AM litter stimulated respiration more than did ECMlitter, owing to the lower C:N of AM litter. Matching the mycorrhizal identity of litter and soilresulted in a difference in total respiration, such that combinations of AM litters with AM soils lostmore C than did combinations of ECM litters with ECM soils.4. Synthesis. Our findings demonstrate that AM and ECM trees have differing indirect effects onsoil decomposer activity through the decomposers they cultivate and/or the quality of organic matterthey produce. Mycorrhizal differences in litter quality accentuate these effects on soil C loss andmay explain patterns in soil C dynamics in terrestrial ecosystems

Citation

Taylor, Melanie K.; Lankau, Richard A.; Wurzburger, Nina; de Vries, Franciska. 2016. Mycorrhizal associations of trees have different indirect effects on organic matter decomposition. Journal of Ecology. 9p.  10.1111/1365-2745.12629