Contrasting effects of nitrogen availability on plant carbon supply to mycorrhizal fungi and saprotrophs - a hypothesis based on field observations in boreal forest
Author
Summary, in 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.
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.
Department/s
Publishing year
2003
Language
English
Pages
225-238
Publication/Series
New Phytologist
Volume
160
Issue
1
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Document type
Journal article
Publisher
Wiley-Blackwell
Topic
- Ecology
- Soil Science
Status
Published
Research group
- Microbial Ecology
ISBN/ISSN/Other
- ISSN: 1469-8137