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Contrasting effects of nitrogen availability on plant carbon supply to mycorrhizal fungi and saprotrophs - a hypothesis based on field observations in boreal forest

Author:
  • Mona N. Högberg
  • Erland Bååth
  • Anders Nordgren
  • Kristina Arnebrant
  • Peter Högberg
Publishing year: 2003
Language: English
Pages: 225-238
Publication/Series: New Phytologist
Volume: 160
Issue: 1
Document type: Journal article
Publisher: Wiley-Blackwell

Abstract english

Soil microorganisms are considered C-limited, while plant productivity is frequently N-limited. Large stores of organic C in boreal forest soils are attributed to negative effects of low temperature, soil acidity and plant residue recalcitrance upon microbial activity.

We examined microbial activity, biomass and community composition along a natural 90-m-long soil N supply gradient, where plant species composition varies profoundly, forest productivity three-fold and soil pH by three units.

There was, however, no significant variation in soil respiration in the field across the gradient. Neither did microbial biomass C determined by fumigation-extraction vary, while other estimates of activity and biomass showed a weak increase with increasing N supply and soil pH. Simultaneously, a phospholipid fatty acid attributed mainly to mycorrhizal fungi declined drastically, while bacterial biomass increased.

We hypothesize that low N supply and plant productivity, and hence low litter C supply to saprotrophs is associated with a high plant C supply to mycorrhizal fungi, while the reverse occurs under high N supply. This should mean that effects of N availability on C supply to these functional groups of microbes acts in opposing directions.

Keywords

  • Ecology
  • Soil Science

Other

Published
  • Microbial Ecology
  • ISSN: 1469-8137
Erland Bååth
E-mail: erland [dot] baath [at] biol [dot] lu [dot] se

Professor emeritus

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