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- Blasko, Robert, et al.
(författare)
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Shifts in soil microbial community structure, nitrogen cycling and the concomitant declining N availability in ageing primary boreal forest ecosystems
- 2015
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 91, s. 200-211
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Tidskriftsartikel (refereegranskat)abstract
- Plant growth in boreal forests is commonly limited by a low supply of nitrogen, a condition that may be aggravated by high tree below-ground allocation of carbon to ectomycorrhizal (ECM) fungi and associated microorganisms. These in turn immobilise N and reduce its availability to plants as boreal ecosystems develop. Here, we studied a boreal forest ecosystem chronosequence created by new land rising out of the sea due to iso-static rebound along the coast of northern Sweden. We used height over the ocean to estimate ecosystem age and examined its relationship to soil microbial community structure and the gross turnover of N. The youngest soils develop with meadows by the coast, followed by a zone of N2-fixing alder trees, and primary boreal conifer forest on ground up to 560 years old. The young soils in meadows contained little organic matter and microbial biomass per unit area. Nitrogen was turned over at low rates when expressed per area (m(-2)), but specific rates (per gram soil carbon (C)) were the highest found along the transect. In the zone with alder, the amounts of soil C and microbial biomass were much higher (bacterial biomass had doubled and fungal biomass quadrupled). Rates of gross N mineralisation (expressed on an area basis) were highest, but the retention of added labelled NH4+ was lowest in this soil as compared to other ages. The alder zone also had the largest extractable pools of inorganic N in soil and highest N % in plant foliage. In the older conifer forest ecosystems the amounts of soil C and N, as well as biomass of both bacteria and fungi increased. Data on organic matter C-14 suggested that the largest input of recently fixed plant C occurred in the younger coniferous forest ecosystems. With increasing ecosystem age, the ratio of microbial C to total soil C was constant, whereas the ratio of microbial N to total soil N increased and gross N mineralization declined. Simultaneously, plant foliar N % decreased and the natural abundance of N-15 in the soil increased. More specifically, the difference in delta N-15 between plant foliage and soil increased, which is related to relatively greater retention of N-15 relative to N-14 by ECM fungi as N is taken up from the soil and some N is transferred to the plant host. In the conifer forest, where these changes were greatest, we found increased fungal biomass in the F- and H-horizons of the mor-layer, in which ECM fungi are known to dominate (the uppermost horizon with litter and moss is dominated by saprotrophic fungi). Hence, we propose that the decreasing availability of N to the plants and the subsequent decline in plant production in ageing boreal forests is linked to high tree belowground C allocation to ECM fungi, a strong microbial sink for available soil N. (C) 2015 The Authors. Published by Elsevier Ltd.
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- Högberg, Mona N, et al.
(författare)
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The return of an experimentally N-saturated boreal forest to an N-limited state : observations on the soil microbial community structure, biotic N retention capacity and gross N mineralisation
- 2014
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Ingår i: Plant and Soil. - : Springer Netherlands. - 0032-079X .- 1573-5036. ; 381:1-2, s. 45-60
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Tidskriftsartikel (refereegranskat)abstract
- To find out how N-saturated forests can return to an N-limited state, we examined the recovery of biotic N sinks under decreasing N supply. We studied a 40-year-old experiment in Pinus sylvestris forest, with control plots, N0, three N treatments, N1-N3, of which N3 was stopped after 20 years, allowing observation of recovery. In N3, the N concentration in foliage was still slightly elevated, but the N uptake capacity of ectomycorrhizal (ECM) roots in N3 was no longer lower than in N0. Per area the amount of a biomarker for fungi, here mainly attributed ECM, was higher in N3 and N0 than in N1 and N2. Retention of labeled (NH4)-N-15 (+) by the soil was greater in the control (99 %) and N3 (86 %), than in N1 (45 %) and N2 (29 %); we ascribe these differences to biotic retention because cation exchange capacity did not vary. Gross N mineralisation and retention of N correlated, negatively and positively, respectively, with abundance of ECM fungal biomarker. The results suggest a key role for ECM fungi in regulating the N cycle. We propose, in accordance with plant C allocation theory, that recovery is driven by increased tree below-ground C allocation to ECM roots and fungi.
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- Noc, Marko, et al.
(författare)
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A multicentre, prospective, randomised controlled trial to assess the safety and effectiveness of cooling as an adjunctive therapy to percutaneous intervention in patients with acute myocardial infarction : The COOL AMI EU Pivotal Trial
- 2021
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Ingår i: EuroIntervention. - 1774-024X. ; 17:6, s. 466-473
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Tidskriftsartikel (refereegranskat)abstract
- Background: Despite primary PCI (PPCI), ST-elevation myocardial infarction (STEMI) can still result in large infarct size (IS). New technology with rapid intravascular cooling showed positive signals for reduction in IS in anterior STEMI. Aims: We investigated the effectiveness and safety of rapid systemic intravascular hypothermia as an adjunct to PPCI in conscious patients, with anterior STEMI, without cardiac arrest. Methods: Hypothermia was induced using the ZOLL® Proteus™ intravascular cooling system. After randomisation of 111 patients, 58 to hypothermia and 53 to control groups, the study was prematurely discontinued by the sponsor due to inconsistent patient logistics between the groups resulting in significantly longer total ischaemic delay in the hypothermia group (232 vs 188 minutes; p<0.001). Results: There were no differences in angiographic features and PPCI result between the groups. Intravascular temperature at wire crossing was 33.3+0.9°C. Infarct size/left ventricular (IS/LV) mass by cardiac magnetic resonance (CMR) at day 4-6 was 21.3% in the hypothermia group and 20.0% in the control group (p=0.540). Major adverse cardiac events at 30 days increased non-significantly in the hypothermia group (8.6% vs 1.9%; p=0.117) while cardiogenic shock (10.3% vs 0%; p=0.028) and paroxysmal atrial fibrillation (43.1% vs 3.8%; p<0.001) were significantly more frequent in the hypothermia group. Conclusions: The ZOLL Proteus intravascular cooling system reduced temperature to 33.3°C before PPCI in patients with anterior STEMI. Due to inconsistent patient logistics between the groups, this hypothermia protocol resulted in a longer ischaemic delay, did not reduce IS/LV mass and was associated with increased adverse events.
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