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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(s) -
Högberg Mo.,
Bååth Erland,
Nordgren Anders,
Arnebrant Kristina,
Högberg Peter
Publication year - 2003
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1046/j.1469-8137.2003.00867.x
Subject(s) - biomass (ecology) , biology , agronomy , soil water , taiga , productivity , ectomycorrhiza , mycorrhiza , microbial population biology , environmental science , botany , ecology , bacteria , symbiosis , genetics , economics , macroeconomics
Summary• 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.