Ectomycorrhizal Production Phenology Follows Roots but Varies by Host Tree Species
Authors
Nicholas Medina1* (nmedina@mortonarb.org), Kelsey Patrick2, Marvin Lo1, Newton Tran1, Colleen Iversen3, Peter Kennedy4, M. Luke McCormack1
Institutions
1Center for Tree Science, Morton Arboretum, Lisle, IL; 2Biological Sciences, University of Illinois, Chicago, IL; 3Oak Ridge National Laboratory, Oak Ridge, TN; 4Plant and Microbial Biology, University of Minnesota, Minneapolis, MN;
Abstract
Mycorrhizal symbioses account for 15 to 45% of forest productivity, but empirical estimates remain uncertain. Belowground phenology, which differs notably in timing from leaf production, constrains the temporal distribution of carbon allocation to roots and fungi. Mycorrhizal root and hyphal production can also differ by plant functional type, tree and fungal species, and environmental conditions. To improve the collective ability to model land carbon dynamics, researchers are measuring mycorrhizal fungal phenology with monthly sampling of roots and soils across a diverse set of 10 monodominant stands of common temperate tree species at the Morton Arboretum in Chicago, IL, U.S. Annual sampling dates align with key tree phenophases and span a broad range of typical soil moisture and temperature values for temperate forests, including a drought period followed by a pulse rain event. The team estimates hyphal production via minirhizotron image scans and qPCR and identify mycorrhizal fungal community shifts with high-throughput amplicon sequencing.
Overall, mycorrhizal root and hyphal production is seasonal, and appears to vary more strongly by tree species than by plant functional type. Net hyphal production peaks in mid-fall, after soils begin to rewet following mid-summer dry down. Ectomycorrhizal hyphae and rhizomorphs peak in production either after or in synchrony with peak fine root production, depending on the specific host tree species. In some cases, a peak in rhizomorph production in spring with little hyphal growth was observed. Researchers expect peak hyphal diversity and production in fall, and for this to be dominated by a few ectomycorrhizal fungal genera, including Lactarius, Suillus, or Amanita as in some previous studies. Future work will link below- and aboveground tree phenology as well as identify drivers of intra- and inter-annual compositional shifts in mycorrhizal fungal communities.