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Carbon and nitrogen relations among soils, microbes and plants in boreal forests

Nordström Högberg, Mona (2004). Carbon and nitrogen relations among soils, microbes and plants in boreal forests. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae. Silvestria, 1401-6230 ; 314
ISBN 91-576-6548-6
[Doctoral thesis]

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Across Fennoscandian boreal forests, variations in hill-slope hydrochemistry cause regular patterns in vegetation composition and forest productivity. The turnover of N, the nutrient limiting plant growth, should be a result of interactions between soils, microbes and plants. This thesis represents a first attempt to describe variations in microbial biomass, community structure and activity associated with these patterns. The main study area was a local 90-mlong natural productivity gradient in northern Sweden, site Betsele, representing three coniferous forest types with increasing productivity: dwarf-shrub (DS), short-herb (SH) and tall-herb (TH) types. Destructive tree girdling was conducted in a DS forest type at another site, Åheden, to enable estimation of the biomass of mycelium of ectomycorrhizal (ECM) fungi. The gradient encompassed the range in soil chemistry and plant community composition in Fennoscandian boreal forests and is thus a useful model for soil-microbialplant interactions. There was also, at this local landscape level, associations between certain soil conditions and plants with specific mycorrhizal types, as proposed typical of different biomes on a continental scale. At Åheden, extramatrical ECM mycelium contributed one third of soil microbial biomass and produced, together with ECM roots, half the dissolved organic carbon. Neither microbial biomass nor soil (root plus microbial) respiration rates varied along the forest productivity gradient. This was unexpected because of the large variation in forest productivity. Gross N mineralization rate increased roughly in proportion to this three-fold increase in productivity. Thus, in contrast to the conventional view, higher rates of N mineralization were not caused by higher microbial activity in general. The susceptibility of the microbial activity of mor soils to physical disturbance decreased when soil fertility increased from the DS to the TH forest type; this was paralleled by a drastic decrease in fungal biomass. Variations in the contribution of mycorrhizal fungi to the microbial biomass confound interpretations of relations among soil and microbial C/N ratios and soil N mineralization. I hypothesize that low N supply and plant productivity, and hence low litter C supply to saprotrophs are associated with a high plant C supply to mycorrhizal fungi, while the reverse occurs under high N supply. Thus, effects of N availability on C supply to these functional groups of microbes acts in opposing directions.

Authors/Creators:Nordström Högberg, Mona
Title:Carbon and nitrogen relations among soils, microbes and plants in boreal forests
Series Name/Journal:Acta Universitatis Agriculturae Sueciae. Silvestria
Year of publishing :September 2004
Number of Pages:44
ALLI. Giesler, R., Högberg, M. and Högberg, P. (1998). Soil chemistry and plants in Fennoscandian boreal forest as exemplified by a local gradient. Ecology 79, 119-137. II. Högberg, M. N. and Högberg, P. (2002). Extramatrical ectomycorrhizal mycelium contributes one-third of microbial biomass and produces, together with associated roots, half the dissolved organic carbon in a forest soil. New Phytologist 154, 791-795. III. Högberg, M. N., Bååth, E., Nordgren, A., Arnebrant, K. and Högberg, P. (2003). Contrasting effects of nitrogen availability on plant carbon supply to mycorrhizal fungi and saprotrophs - a hypothesis based on field observations in boreal forest. New Phytologist 160, 225-238. IV. Högberg, M. N., Nordgren, A. and Högberg, P. (0000). Large variability in sensitivity of microbial activity to physical disturbance among morlayers from boreal forest. (Manuscript). V. Högberg, M. N., Myrold, D. D., Giesler, R. and Högberg, P. (0000). Shifts in soil nitrogen dynamics along a local plant productivity gradient in boreal forest. (Manuscript).
Place of Publication:Uppsala
ISBN for printed version:91-576-6548-6
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:P Natural resources > P34 Soil biology
Subjects:Not in use, please see Agris categories
Agrovoc terms:nitrogen cycle, carbon, mineralization, primary productivity, biomass, mycorrhizae, forest soils, boreal forests
Keywords:forest productivity gradient, mor-soils, microbial, biomass, activity, community structure, mycorrhizal fungi, saprothrophs, C allocation, N supply, gross N mineralisation/immobilisation, N-limitation
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ID Code:609
Department:(S) > Institutionen för skoglig mykologi och patologi
Deposited By: Staff Epsilon
Deposited On:02 Sep 2004 00:00
Metadata Last Modified:02 Dec 2014 10:05

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