Carbon sequestration is related to mycorrhizal fungal community shifts during long-term succession in boreal forests

New Phytol. 2015 Mar;205(4):1525-36. doi: 10.1111/nph.13208. Epub 2014 Dec 11.

Abstract

Boreal forest soils store a major proportion of the global terrestrial carbon (C) and below-ground inputs contribute as much as above-ground plant litter to the total C stored in the soil. A better understanding of the dynamics and drivers of root-associated fungal communities is essential to predict long-term soil C storage and climate feedbacks in northern ecosystems. We used 454-pyrosequencing to identify fungal communities across fine-scaled soil profiles in a 5000 yr fire-driven boreal forest chronosequence, with the aim of pinpointing shifts in fungal community composition that may underlie variation in below-ground C sequestration. In early successional-stage forests, higher abundance of cord-forming ectomycorrhizal fungi (such as Cortinarius and Suillus species) was linked to rapid turnover of mycelial biomass and necromass, efficient nitrogen (N) mobilization and low C sequestration. In late successional-stage forests, cord formers declined, while ericoid mycorrhizal ascomycetes continued to dominate, potentially facilitating long-term humus build-up through production of melanized hyphae that resist decomposition. Our results suggest that cord-forming ectomycorrhizal fungi and ericoid mycorrhizal fungi play opposing roles in below-ground C storage. We postulate that, by affecting turnover and decomposition of fungal tissues, mycorrhizal fungal identity and growth form are critical determinants of C and N sequestration in boreal forests.

Keywords: 454-sequencing; Betula pubescens; Picea abies; Pinus sylvestris; boreal forest; carbon (C) sequestration; ectomycorrhizal exploration types; mycorrhizal symbiosis.

MeSH terms

  • Biodiversity
  • Carbon Sequestration*
  • Ecosystem*
  • Islands
  • Models, Biological
  • Mycorrhizae / physiology*
  • Phylogeny
  • Species Specificity
  • Sweden
  • Taiga*
  • Time Factors