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Research article - Peer-reviewed, 2003

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

Hogberg MN, Baath E, Nordgren A, Arnebrant K, Hogberg P


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


boreal forest; carbon supply; microbioal biomass; mycorrhizal fungi; nitrogen availability; saprotrophs; soil sampling; soil pH

Published in

New Phytologist
2003, Volume: 160, number: 1, pages: 225-238

    SLU Authors

      • Nordgren, Anders

        • Department of Forest Ecology, Swedish University of Agricultural Sciences
        • Högberg, Peter

          • Department of Forest Ecology, Swedish University of Agricultural Sciences

        UKÄ Subject classification

        Environmental Sciences related to Agriculture and Land-use

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