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  • 1.
    Arnebrant, Kriatina
    et al.
    Department of Microbial Ecology, University of Lund, Lund, Sweden.
    Schnürer, Johan
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Changes in atp content during and after chloroform fumigation1990In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 22, no 6, p. 875-877Article in journal (Refereed)
  • 2. Bahr, Adam
    et al.
    Ellström, Magnus
    Akselsson, Cecilia
    Ekblad, Alf
    Örebro University, School of Science and Technology.
    Mikusinska, Anna
    Örebro University, School of Science and Technology.
    Wallander, Håkan
    Growth of ectomycorrhizal fungal mycelium along a Norway spruce forest nitrogen deposition gradient and its effect on nitrogen leakage2013In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 59, p. 38-48Article in journal (Refereed)
    Abstract [en]

    Almost all boreal and temperate forest tree species live in symbiosis with ectomycorrhizal fungi (EMF); the trees transfer carbon (C) to the fungi in exchange for nutrients and water. Several studies have shown that experimental application of inorganic nitrogen (N) represses production of EMF extramatrical mycelia (EMM), but studies along N deposition gradients are underrepresented. Other environmental variables than N may influence EMM production and in this study we included 29 thoroughly monitored Norway spruce stands from a large geographical region in Sweden in order to evaluate the importance of N deposition on EMM growth and N leaching in a broader context. It was concluded that N deposition was the most important factor controlling EMM production and that the amounts typically deposited in boreal and boreo-nemoral regions can be sufficient to reduce EMM growth. Other factors, such as phosphorus status and pH, were also correlated with EMM production and should be considered when predicting EMM growth and N leaching. We also showed that EMM production substantially contributed to the C sequestration (320 kg ha(-1) yr(-1)), suggesting that it should be included in C cycle modelling. Furthermore, EMF are probably important for the N retention capacity since high N leaching coincided with low EMM growth. However, it was not possible to differentiate between the effects of EMF and the direct effect of N deposition on N leaching in the present study.

  • 3. Berglund, S. Linnea
    et al.
    Agren, Goran I.
    Ekblad, Alf
    Örebro University, School of Science and Technology.
    Carbon and nitrogen transfer in leaf litter mixtures2013In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 57, p. 341-348Article in journal (Refereed)
    Abstract [en]

    The decomposition rate of litter mixtures can differ from that expected on the basis of the decomposition rate of the individual components. This difference may be linked to nitrogen (N) transfer from high-N to low-N components. Transfer of N is probably also associated with transfer of C, but the extent and direction of this C transfer are unknown. This study examined transfer and loss in laboratory microcosms of C and N from two mixed litter species (Scots pine, Pinus sylvestris L and maize, Zea mays L), which have natural isotopic differences in C-13. Half the material was N-15-labelled and the plants were fertilised or unfertilised. Substantial bidirectional transfer of C and N occurred between the litters, with net transfer of C from pine to maize litter and net transfer of N from high-N to low-N litter. Mixtures of fertilised and unfertilised plant litter showed higher than expected C losses and net transfer of N. Mixtures with litters from the same fertilisation treatment had small or insignificant net transfer of N and their C losses did not differ from values estimated using the decomposition rates of the pure litters.

  • 4.
    Bonde, Torben A.
    et al.
    Department of Water in Environment and Society, University of Linköping, Linköping, Sweden.
    Schnürer, Johan
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Rosswall, Thomas
    Department of Water in Environment and Society, University of Linköping, Linköping, Sweden.
    Microbial biomass as a fraction of potentially mineralizable nitrogen in soils from long-term field experiments1988In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 20, no 4, p. 447-452Article in journal (Refereed)
    Abstract [en]

    Aerobic long-term incubations (40-wk) were employed to measure the potentially mineralizable nitrogen (N0) in five 30-yr old cropping systems. The cropping systems consisted of: (1) bare fallow; (2) cropping with no additions; (3) cropping with 80 kg N ha-1 y-1 as Ca(NO3)2; (4) cropping with 80 kg N ha-1 yr-1 as Ca(NO3)2 plus 1800kg C ha-1 yr-1 as straw; and (5) cropping with 80 kg N ha-1 yr-1 plus 1800 kg C ha-1 yr-1 as farmyard manure. The amounts of N mineralized during the 40-wk incubations were between 93 and 168 μg g-1 (302-543 kg N ha-1 down to 25cm depth) with the lowest value for the fallow and the highest for the farmyard manure treatment. Microbial biomass-C and -N were measured on four occasions during the incubations. The biomass-C showed a rapid decrease to week 4 (to 36% of the initial mass), a slower decrease to week 9 (to 23% of initial mass) and a very slow decline to the final determination at the end of the incubation (to 8% of initial mass). The biomass-N displayed a similar pattern. Two related models were employed to describe the kinetics of N-mineralization during incubation: (1) a two-component first-order; and (2) a simplified special case of the two-component model. In all cases except the straw-amended soil, the simplified two-component model offered the best description of the curves of accumulated mineral-N. The available fraction, Na, of soil organic-N had mineralization rate constants similar to those for mineralization of microbial biomass.

  • 5. Hagedorn, Frank
    et al.
    Hiltbrunner, David
    Streit, Kathrin
    Ekblad, Alf
    Örebro University, School of Science and Technology.
    Lindahl, Bjorn
    Miltner, Anja
    Frey, Beat
    Handa, I. Tanya
    Haettenschwiler, Stephan
    Nine years of CO2 enrichment at the alpine treeline stimulates soil respiration but does not alter soil microbial communities2013In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 57, p. 390-400Article in journal (Refereed)
    Abstract [en]

    Elevated atmospheric CO2 was often shown to stimulate belowground C allocation, but it is uncertain if this increase also alters the structure of soil microbial communities. Here, we assessed the effects of nine years of CO2 enrichment on soil microbial communities of an alpine treeline ecosystem with 35-year-old Lath decidua and Pinus mugo ssp. uncinata trees. We also tracked the C-13 signal of supplemental CO2 in soil-respired CO2, microbial biomass, and phospholipid fatty acids (PLFA) in undisturbed mor-type organic layers. We found a persistently increased soil CO2 efflux (+24% on average), but negligible effects of elevated CO2 on the biomass and community structure of soil microorganisms under both tree species determined with PLFA and T-RFLP (terminal restriction fragment length polymorphism). The C-13 tracing over 9 years revealed that 24-40% of the soil microbial biomass was composed of 'new' plant-derived C. PLFA from gram-negative biomarkers did not significant shift in C-13 by the CO2 addition, while those of gram-negative bacteria were significantly altered. The highest C-13 signals in individual PLFA was found in the fatty acid 18:26)6,9 with 65-80% new C, indicating that new plant-derived C was primarily incorporated by soil fungi. However, CO2 enrichment did not affect the production of mycelia biomass and the structure and composition of the fungal communities analysed by high-throughput 454-sequencing of genetic markers. Collectively, our results suggest that C flux through the plant soil system will be accelerated but that the biomass and composition of microbial communities will be little affected by rising atmospheric CO2 in organic matter rich treeline soils.

  • 6.
    Högberg, Peter
    et al.
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Ekblad, Alf
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Substrate-induced respiration measured in situ in a C-3-plant ecosystem using additions of C-4-sucrose1996In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 28, no 9, p. 1131-1138Article in journal (Refereed)
    Abstract [en]

    We added sucrose derived from sugar cane, a tropical C4-plant, to the soil of a temperate C3-forest plant system. The combined measurement of CO2 respiration rate and 13C natural abundance of CO2 enabled a distinction to be made between C3- and C4-respiration, which offered new possibilities to analyze basal respiration and substrate-induced respiration (SIR) in the field. In tests in the laboratory, through-flow systems were used, while in the field the stationary gas phase under soil covers was sampled. Results from the laboratory and in the field were similar with an average SIR response of 2.2 (range 1.7–2.7) times the basal respiration. The change in δ13C after addition of C4-surcrose was less than expected from the increase in respiration rate. Calculations showed that there was an increased efflux of C3-carbon after the C4-sucrose addition. We describe mathematical models, by which we calculated the various source effects contributing to the measured response. The method has numerous advantages, e.g. it uses naturally labelled inexpensive non-hazardous compounds and measurements are non-destructive to the studied system.

  • 7.
    Johansson, Emma M.
    et al.
    Örebro University, School of Science and Technology.
    Fransson, Petra M. A.
    Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences.
    Finlay, Roger D.
    Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences.
    van Hees, Patrick A. W.
    Örebro University, School of Science and Technology.
    Quantitative analysis of exudates from soil-living basidiomycetes in pure culture as a response to lead, cadmium and arsenic stress2008In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 40, no 9, p. 2225-2236Article in journal (Refereed)
    Abstract [en]

    Six different ectomycorrhizal fungi (Hebeloma velutipes, Piloderma byssinum, Paxillus involutus, Rhizopogonroseolus, Suillus bovinus and Suillus variegatus) and two saprotrophic fungi (Hypholoma fasciculare andHypholoma capnoides) were exposed to metal stress induced by Pb, Cd and As. After pre-growth ina nutrient solution in Petri dishes, metal exposure was performed either in a nutrient rich solution or ina nutrient poor solution for seven days. The fungi were exposed to two different metal concentrations,low and high (Pb: 10 þ 100 mM; Cd: 1 þ 10 mM; As: 1 þ 10 mM). Exudation of low molecular weightorganic compounds (low molecular weight organic acids (LMWOA), amino acids and dissolved monosaccharides),as well as dissolved organic carbon was quantified as a potential response to the metalstress. The main LMWOA identified was oxalate. Oxalate exudation increased significantly in response toboth low and high Pb and Cd concentrations, as well as low As exposure, relative to nutrient controls.Exposure to As and mixtures of metals (Pb þ Cd, Pb þ As) did not result in any significant increase inoxalate production compared to controls. The presence of a carbon source (glucose) in this study islikely to have been important for exudation of organic compounds. For the nutrient rich (þ1mMglucose) metal treatments exposure to Pb and Cd mainly increased exudation of oxalate and total aminoacids. Production of dissolved monosaccharides, as well as DOC, did not increase significantly in responseto metal exposure, irrespective of nutrient conditions. This may be explained by re-absorption ofthe organic compounds by the mycelium or by the fact that metals had no effect on exudation of thesecompounds.

  • 8.
    Johansson, Emma M.
    et al.
    Örebro University, School of Science and Technology.
    Fransson, Petra M. A.
    Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences.
    Finlay, Roger D.
    van Hees, Patrick A. W.
    Örebro University, School of Science and Technology.
    Quantitative analysis of soluble exudates produced by ectomycorrhizal roots as a response to ambient and elevated CO22009In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 41, no 6, p. 1111-1116Article in journal (Refereed)
    Abstract [en]

    Despite its potential impact on soil carbon flow, few studies have attempted to quantify the effects of elevated carbon dioxide (CO2) on production of exudates by mycorrhizal plants. In this study we quantified low molecular weight (LMW) organic compounds exuded by non-mycorrhizal (NM) and ectomycorrhizal (ECM) plants in relation to exposure to elevated CO2. Scots pine seedlings, either colonized by one of eight different ECM fungi or non-mycorrhizal (NM), were exposed to either ambient (350 ppm) or elevated (700 ppm) concentrations of CO2. Exudation of LMW organic acids (LMWOAs), amino acids, dissolved monosaccharides and total dissolved organic carbon (DOC) was determined and exudation rates were calculated per g root and fungal dry mass. CO2 had a significant impact on exudation. Under elevated CO2, exudation of total LMWOAs increased by 120–160%, amino acids by 250%, dissolved monosaccharides by 130–270% and DOC by 180–220% compared to ambient CO2 treatment. Net CO2 assimilation rates increased significantly by 41–47% for seedlings exposed to elevated CO2. Exuded C calculated as a percentage of assimilated CO2 increased by 41–88% in the elevated CO2 treatment compared to ambient CO2 treatment.

  • 9.
    Klemendtsson, Leif
    et al.
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Berg, Per
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Clarholm, Marianne
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Schnürer, Johan
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Rosswall, Thomas
    Department of Water in Environment and Society, University of Linköping, Linköping, Sweden.
    Microbial nitrogen transformations in the root environment of barley1987In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 19, no 5, p. 551-558Article in journal (Refereed)
    Abstract [en]

    To determine the influence of barley roots on microorganisms and N-transfonning processes in soil, numbers of nitrifiers and potential nitrification and denitrification rates were measured every week for 5 wks. The barley plants were grown in growth chambers in which the root-containing soil layer (A) was separated from three outer soil layers (B, C, D). The numbers and biomass of bacteria, numbers of flagellates and amoebae, total and FDA-active hyphal lengths, microbial biomass carbon and respiration were also determined.

    The numbers of ammonium oxidizers were positively correlated with root biomass but did not differ significantly between soil layers. Potential ammonium oxidation was stimulated in the root-layer, while potential nitrite oxidation was stimulated in the B- and C-layers.

    The denitrification activity (measured anaerobically in the presence of excess No- 3) was positively correlated with root biomass in the A-layer. Denitrification activity in the B-layer was positively correlated with the water content of the soil. When roots grew near the nets separating the root layer from the other layers, denitrification activity was stimulated in the next layer (B).

    We propose that nitrite oxidation in the root zone partly depends on the reduction of nitrate. This would explain why nitrite-oxidizer numbers were usually several orders of magnitude higher than ammonium-oxidizer numbers.

    Bacterial numbers decreased between wks 1 and 5. Increases in bacteria, naked amoebae and flagellates in all layers between wks 2 and 3 indicated that bacteria were produced until wk 3. There were no signs of bacterial production after wk 3.

    The total length of hyphae and the length of FDA-active hyphae were not significantly different between layers. However, both of these parameters, as well as total microbial biomass carbon and respiration, were consistently highest in the A-layer.

  • 10.
    Krantz-Rülcker, C.
    et al.
    Department of Water and Environmental Studies, Linköping University, Linköping, Sweden .
    Allard, B.
    Department of Water and Environmental Studies, Linköping University, Linköping, Sweden .
    Schnürer, Johan
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Adsorption of IIB-metals by three common soil fungi-comparison and assessment of importance for metal distribution in natural soil systems1996In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 28, no 7, p. 967-975Article in journal (Refereed)
    Abstract [en]

    Interactions of IIb-elements, Zn, Cd and Hg, with three common soil fungi, Trichoderma harzianum, Penicillium spinulosum and Mortierella isabellina, have been studied. The accumulation of the metals by the fungi was studied as a function of pH at constant ionic strength and at concentration levels of the metals representative of natural systems. Two stages of fungal activity were considered in the experiments. The fungi generally exhibited high affinity for metal ions indicated by distribution coefficients (log K-d, in 1 kg(-1)) of about 3.5 +/- 1, 2.5 +/- 1 and 4 +/- 1 for Zn, Cd and Hg, respectively. The pH-dependence of the accumulation as well as the isotherms at constant pH were similar between the fungi, and the maximum capacities were at least 50 mmoles kg(-1) mycelium (dw). Metal accumulation by starved mycelia was almost independent of pH, while non-starved mycelia in two cases accumulated more metals at low pH. Calculations of the distribution of metals in a model soil system of inorganic and organic constituents as well as fungal biomass indicated that the amounts of metal associated to the fungi are negligible at neutral pH. However, due to the ability of these fungi to accumulate metals independently of pH, the fraction of metals associated to fungal biomass at low pH may be significant, and, in some cases, predominant. This illustrates that the effects of fungi on metal distribution in soil should not be neglected, e.g. during a progressing acidification.

  • 11.
    Lundberg, Peter
    et al.
    Linköping University, Linköping, Sweden.
    Ekblad, Alf
    Örebro University, School of Science and Technology. Swedish University of Agricultural Sciences, Umeå, Sweden.
    Nilsson, Mats
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    C-13 NMR spectroscopy studies of forest soil microbial activity: glucose uptake and fatty acid biosynthesis2001In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 33, no 4-5, p. 621-632Article in journal (Refereed)
    Abstract [en]

    The intimate association of soil microorganisms with the soil matrix complicates analysis of their metabolism, since thorough separation of intact cells from the matrix is very difficult using standard protocols. Thus, in the study reported here, in situ glucose decomposition and metabolism in humus from a coniferous forest soil was monitored and evaluated using ‘solution state’ 13C NMR, which can be used in a non-invasive manner. [U-13C] glucose was added at a concentration of 1.73 mmol C g−1 dry organic matter, which is known to allow maximal substrate induced respiration (SIR), and the microbial metabolism of the added C was followed over a period of 28 days. The data showed that ∼50% of the added glucose was consumed within three days, coinciding with the appearance of label in CH3, –CH2– and –CH=CH– groups, and in glycerol-carbons, suggesting that olefinic triacylglycerols were being formed, probably located in oil droplets. During days two to three, around 40% of the consumed glucose C was allocated into solid state components, about 40% was respired and about 20% was found as triglycerols. The triacylglycerol signal reached a maximum after 13 days, but subsequently declined by 60%, as the triacylglycerols were apparently consumed, by day 28 of the incubation. Our results indicate there was an initial formation of structural microbial C (solid state carbon) followed by formation of storage lipid C, which subsequently decreased, probably because it was used to provide the organisms with energy when the external energy source (i.e. the glucose) was depleted. The formation of unsaturated triacylglycerols, typical storage metabolites of eucaryotes, suggests that fungi were the most active organisms in the glucose degradation.

  • 12.
    Mikusinska, Anna
    et al.
    Örebro University, School of Science and Technology.
    Persson, Tryggve
    Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Taylor, Andy F. S.
    The James Hutton Institute, Aberdeen, UK.
    Ekblad, Alf
    Örebro University, School of Science and Technology.
    Response of ectomycorrhizal extramatrical mycelium production and isotopic composition to in-growth bag size and soil fauna2013In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 66, p. 154-162Article in journal (Refereed)
    Abstract [en]

    In-growth bags are increasingly used to study extramatrical mycelium (EMM) of ectomycorrhizal fungi in forest soils. In this paper we tested whether bag size and presence of soil fauna in bags influence the production, isotopic composition, carbon (C) and nitrogen (N) content of the EMM. Cylindrical in-growth mesh bags (2- or 5-cm-diameter; with or without openings - (1 or 2 mm), allowing faunal colonization or not) were harvested 37, 48, 81 and 283 days after installation in July and the EMM biomass was determined from elemental analyses of the extractable amount of mycelia. The occurrence of openings allowed animals to invade the bags but this did not affect the amount of EMM. We suggest further studies in this matter since the number of animals was low and variable. In the first harvest, mycelial biomass C was three times greater in 2-cm than in 5-cm-bags. After 81 days, mycelial biomass C was 54% greater in the 2-cm (54 kg ha(-1)) than in the 5-cm bags (35 kg ha(-1)). While total mycelial C did not change over winter, N content increased suggesting a role for the EMM in the storage of N from autumn to spring. The delta C-13 and delta N-15 of the EMM changed between the first three harvests. We hypothesize these changes to be mainly driven by changes in plant C and N sinks. The relation between the isotopic composition of sporocarp exploration type, plant roots and EMM is discussed. (C) 2013 Elsevier Ltd. All rights reserved.

  • 13.
    Paustian, Keith
    et al.
    Departments of Ecology and Environmental Research, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Schnürer, Johan
    Departments of Ecology and Environmental Research, Swedish University of Agricultural Sciences, Uppsala, Sweden; Departments Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Fungal growth response to carbon and nitrogen limitation: A theoretical model1987In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 19, no 5, p. 613-620Article in journal (Refereed)
    Abstract [en]

    A model of fungal growth in soil is described. Two biomass components, cell walls and cytoplasm are considered. Allocation of assimilates to cell wall and cytoplasm synthesis and the relative rate of cytoplasm translocation vary according to C and N availabilities.

    Model behaviour in relation to substrate supply is examined. For single substrate additions, active mycelium (cytoplasm-filled hyphae) shows a positive correlation to substrate availability, while total hyphal length (cytoplasm-filled + evacuated hyphae) shows an inverse response. For continuous substrate additions, the model predicts that equilibrium levels of active mycelium depend primarily on substrate input rate and yield efficiency and are independent of other parameters controlling substrate availability.

    Model assumptions about biosynthate allocation and cytoplasm translocation influence N mineralization and immobilization patterns. The model suggests that critical C:N ratios change during decomposition as the fungal biomass develops. The advantages conferred by the mycclial growth form, in terms of conserving energy and nutrient elements in resource-poor environments, are discussed.

  • 14.
    Paustian, Keith
    et al.
    Departments of Ecology and Environmental Research, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Schnürer, Johan
    Departments of Ecology and Environmental Research, Swedish University of Agricultural Sciences, Uppsala, Sweden; Departments of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Fungal growth response to carbon and nitrogen limitation: Application of a model to laboratory and field data1987In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 19, no 5, p. 621-629Article in journal (Refereed)
    Abstract [en]

    We evaluated assumptions about fungal growth regulation by applying a model to laboratory and field experimental data. Hyphal length, dry weight, CO2, solution N and solution C were measured during 140 h incubations in liquid batch cultures of Trichoderma harzianum on mineral media at three nitrogen concentrations. Assuming preferential allocation of N to maintain hyphal extension and including cytoplasm translocation gave the best agreement between model predictions and observed data for N-limited growth. When excluding translocation from the model, hyphal length increase could not be well predicted.

    Fungal growth in an arable soil was simulated for two soil moisture regimes; one receiving rainfall only and one maintained in a moist condition by daily irrigation. Simulations were compared to measured total hyphal length, FDA-active hyphae and O2-consumption. Model results suggested that hyphal length increases were highly subsidized by translocation of cytoplasm. The response of the active biomass component to soil moisture conditions primarily influenced substrate availability.

  • 15.
    Robertson, Kerstin
    et al.
    Department of Water in Environment and Society, Linköping University, Linköping, Sweden.
    Schnürer, Johan
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Clarholm, Marianne
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Bonde, Torben A.
    Department of Water in Environment and Society, Linköping University, Linköping, Sweden.
    Rosswall, Thomas
    Department of Water in Environment and Society, Linköping University, Linköping, Sweden.
    Microbial biomass in relation to C and N mineralization during laboratory incubations1988In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 20, no 3, p. 281-286Article in journal (Refereed)
    Abstract [en]

    Net carbon and nitrogen mineralization rates were determined for an arable soil during 12 weeks at 37†C using an aerobic incubation-leaching technique. The amounts of mineralized C and N were compared to changes in the contents of C and N in microbial biomass (as determined by the chloroform fumigation incubation method; CFIM) during the incubation and to amounts of organic C and N in the leachates. Microorganisms were also followed by direct counting of bacteria, measurements of total hyphal lengths and fluorescein diacetate (FDA)-active hyphae, and by most probable number determinations of protozoa (naked amoebae and flagellates).

    Numbers of naked amoebae increased nearly 10-fold initially and then decreased between weeks 6 and 12. Bacterial numbers and FDA-active hyphae decreased during the incubation, and the relative composition changed slightly in favour of bacteria. Total hyphal lengths remained almost constant.

    A total of 105 μg N g'- soil dry wt and 1179 μg C g- soil dry wt was mineralized during the incubation, while the microbial N pool decreased by 42 γm- soil dry wt and the microbial C pool decreased by 225μ g- soil dry wt. Soluble organic matter in the leachates amounted to 16 and 31% of mineralized C and N, respectively.

    The possibility of measuring C mineralization with less frequent teachings and determinations of N mineralization offers an easy method for assessing changes in labile soil organic matter over time or for comparisons between soils. Through the use of appropriate C-to-N ratios, the N-content in the labile pool can be calculated.

  • 16.
    Schnürer, Johan
    et al.
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Clarholm, Marianne
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Rosswall, Thomas
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Microbial biomass and activity in an agricultural soil with different organic matter contents1985In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 17, no 5, p. 611-618Article in journal (Refereed)
    Abstract [en]

    Changes in soil fertility caused by various organic and N-fertilizer amendments were studied in a long-term field trial mostly cropped with cereals. Five treatments were included: (I) fallow, (II) cropping with no C or N addition, (III) cropping with N-fertilization (80 kg ha -1 yr-1), (IV) cropping with straw incorporation (1800kg Cha-1 yr-1) and N-fertilization (80 kg ha-1yr-1), and (V) cropping with addition of farmyard manure (80 kg N + 1800kg Cha-1yr-1). The treatments resulted in soil organic matter contents ranging from 4.3% (I) to 5.8% (V). Microbial biomass and activity were determined by chloroform fumigation, direct counting of fungi (fluorescein diacetate (FDA)-staining and Jones-Mollison agar-film technique) and bacteria (acridine orange staining), most probable number determinations of protozoa, esterase activity (total FDA hydrolysis) and respiration. Both biomass estimates and activity measurements showed a highly significant correlation with soil organic matter. Microbial biomass C ranged from 230 to 600 μg C g-1 dry wt soil, as determined by the fumigation technique, while conversions from direct counts gave a range from 380 to 2260 μg C. Mean hyphal diameters and mean bacterial cell volumes decreased with decreasing soil organic matter content.

  • 17. Wallander, H.
    et al.
    Ekblad, Alf
    Örebro University, School of Science and Technology.
    Godbold, D. L.
    Johnson, D.
    Bahr, A.
    Baldrian, P.
    Bjork, R. G.
    Kieliszewska-Rokicka, B.
    Kjoller, R.
    Kraigher, H.
    Plassard, C.
    Rudawska, M.
    Evaluation of methods to estimate production, biomass and turnover of ectomycorrhizal mycelium in forests soils: a review2013In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 57, p. 1034-1047Article, review/survey (Refereed)
    Abstract [en]

    Mycorrhizal fungi constitute a considerable sink for carbon in most ecosystems. This carbon is used for building extensive mycelial networks in the soil as well as for metabolic activity related to nutrient uptake. A number of methods have been developed recently to quantify production, standing biomass and turnover of extramatrical mycorrhizal mycelia (EMM) in the field. These methods include minirhizotrons, in-growth mesh bags and cores, and indirect measurements of EMM based on classification of ectomycorrhizal fungi into exploration types. Here we review the state of the art of this methodology and discuss how it can be developed and applied most effectively in the field, Furthermore, we also discuss different ways to quantify fungal biomass based on biomarkers such as chitin, ergosterol and PLFAs, as well as molecular methods, such as qPCR. The evidence thus far indicates that mycorrhizal fungi are key components of microbial biomass in many ecosystems. We highlight the need to extend the application of current methods to focus on a greater range of habitats and mycorrhizal types enabling incorporation of mycorrhizal fungal biomass and turnover into biogeochemical cycling models.

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