DOI: 10.5061/dryad.6q573n5wf
title: Identifying functional impacts of heat-resistant fungi on boreal forest recovery after wildfire

description: Fungi play key roles in carbon (C) dynamics of ecosystems: saprotrophs
 decompose organic material and return C in the nutrient cycle, and
 mycorrhizal species support plants that accumulate C through
 photosynthesis. The identities and functions of extremophile fungi present
 after fire can influence C dynamics, particularly because plant-fungal
 relationships are often species-specific. However, little is known about
 the function and distribution of fungi that survive fires. We aim to
 assess the distribution of heat-resistant soil fungi across burned stands
 of boreal forest in the Northwest Territories, Canada, and understand
 their functions in relation to decomposition and tree seedling growth. We
 cultured and identified fungi from heat-treated soils and linked sequences
 from known taxa with high throughput sequencing fungal data (Illumina
 MiSeq, ITS1) from soils collected in 47 plots. We assessed functions under
 controlled conditions by inoculating litter and seedlings with
 heat-resistant fungi to assess decomposition and effects on seedling
 growth, respectively, for black spruce (Picea mariana), birch (Betula
 papyrifera), and jack pine (Pinus banksiana). We also measured litter
 decomposition rates and seedling densities in the field without
 inoculation. We isolated seven taxa of heat-resistant fungi and found
 their relative abundances were not associated with environmental or fire
 characteristics. Under controlled conditions, Fayodia gracilipes and
 Penicillium arenicola decomposed birch, but no taxa decomposed black
 spruce litter significantly more than the control treatment. Seedlings
 showed reduced biomass and/or mortality when inoculated with at least one
 of the fungal taxa. Penicillium turbatum reduced growth and/or caused
 mortality of all three species of seedlings. In the field, birch litter
 decomposed faster in stands with greater pre-fire proportion of black
 spruce, while black spruce litter decomposed faster in stands experiencing
 longer fire-free intervals. Densities of seedlings that had germinated
 since fire were positively associated with ectomycorrhizal richness while
 there were fewer conifer seedlings with greater heat-resistant fungal
 abundance. Overall, our study suggests that extremophile fungi present
 after fires have multiple functions and may have unexpected negative
 effects on forest functioning and regeneration. In particular,
 heat-resistant fungi after fires may promote shifts away from conifer
 dominance that are observed in these boreal forests.    
description: Fungi were isolated into pure culture from heat-treated soils
 that had burned the previous year. These were inoculated on to litter of
 paper birch and black spruce to assess decomposition (mass lost) under
 controlled conditions. Fungi were also inoculated on to roots of seedlings
 of paper birch, black spruce, and jack pine to assess impacts on biomass
 (grams after dried). Sanger sequences of cultured fungi
 were matched with that of sequences from high throughput amplicon
 sequencing (MiSeq Illumina) at 47 plots. In situ
 decomposition (mass lost) of black spruce and paper birch litter was
 assessed after 12 and 24 months from 5 litterbags 30 plots in the field
 2-4 years after fire. Seedlings were counted in 3, 1 by
 1 m quadrats per plot one year after fire at 47 plots.
  
description: Each data file has a metadata sheet Fungal
 cultures are in the Canadian Collection of Fungal Cultures (DAOMC 251855 –
 251868) Sanger sequences for fungal cultures are in
 Genbank (MN410597-MN410606)