| 1. |
- Aguetoni Cambui, Camila, et al.
(författare)
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Patterns of Plant Biomass Partitioning Depend on Nitrogen Source
- 2011
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen (N) availability is a strong determinant of plant biomass partitioning, but the role of different N sources in this process is unknown. Plants inhabiting low productivity ecosystems typically partition a large share of total biomass to belowground structures. In these systems, organic N may often dominate plant available N. With increasing productivity, plant biomass partitioning shifts to aboveground structures, along with a shift in available N to inorganic forms of N. We tested the hypothesis that the form of N taken up by plants is an important determinant of plant biomass partitioning by cultivating Arabidopsis thaliana on different N source mixtures. Plants grown on different N mixtures were similar in size, but those supplied with organic N displayed a significantly greater root fraction. (15)N labelling suggested that, in this case, a larger share of absorbed organic N was retained in roots and split-root experiments suggested this may depend on a direct incorporation of absorbed amino acid N into roots. These results suggest the form of N acquired affects plant biomass partitioning and adds new information on the interaction between N and biomass partitioning in plants.
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| 2. |
- Boberg, Johanna, et al.
(författare)
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Nitrogen availability affects saprotrophic basidiomycetes decomposing pine needles in a long term laboratory study
- 2011
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Ingår i: Fungal Ecology. - : Elsevier BV. - 1754-5048 .- 1878-0083. ; 4, s. 408-416
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Tidskriftsartikel (refereegranskat)abstract
- Fungi, especially basidiomycetous litter decomposers, are pivotal to the turnover of soil organic matter in forest soils. Many litter decomposing fungi have a well-developed capacity to translocate resources in their mycelia, a feature that may significantly affect carbon (C) and nitrogen (N) dynamics in decomposing litter. In an eight-month long laboratory study we investigated how the external availability of N affected the decomposition of Scots pine needles, fungal biomass production, N retention and N-mineralization by two litter decomposing fungi - Marasmius androsaceus and Mycena epipterygia. Glycine additions had a general, positive effect on fungal biomass production and increased accumulated needle mass loss after 8 months, suggesting that low N availability may limit fungal growth and activity in decomposing pine litter. Changes in the needle N pool reflected the dynamics of the fungal mycelium. During late decomposition stages, redistribution of mycelium and N out from the decomposed needles was observed for M. epipterygia, suggesting autophagous self degradation. (C) 2011 Elsevier Ltd and The British Mycological Society. All rights reserved.
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| 3. |
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| 4. |
- Gruffman, Linda, et al.
(författare)
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Cultivation of Norway spruce and Scots pine on organic nitrogen improves seedling morphology and field performance
- 2012
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 276, s. 118-124
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen availability exerts a significant control on biomass allocation of plants including Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris (L)) in boreal forest ecosystems. Recent studies suggest, however, this control differs for inorganic and organic nitrogen sources. The importance of the chemical form of nitrogen (inorganic or organic) for the morphology and growth of conifer seedlings was studied during production of seedlings in a forest nursery and subsequently in a field trial in northern Sweden. Seedlings were supplied with two different nutrient solutions; an inorganic conventional fertilizer and an organic, amino acid-based fertilizer. Seedlings cultivated on the organic nitrogen source displayed larger root systems resulting in a higher root: shoot ratio than did seedlings cultivated on the inorganic nitrogen source. The proportion of fine roots to lateral roots and the root tip proportion colonized by mycorrhiza were positively affected by the organic nitrogen source. Norway spruce seedlings cultivated on organic nitrogen displayed significantly increased shoot growth compared to seedlings cultivated on inorganic nitrogen. Our results suggest that the chemical form of nitrogen influences the allocation of biomass in conifer seedlings. The shift in allocation of resources to root biomass further leads to a competitive advantage in field conditions, resulting in a significant increase in shoot growth one year following transplant. (C) 2012 Elsevier B.V. All rights reserved.
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| 5. |
- Gruffman, Linda, et al.
(författare)
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Plant nitrogen status and co-occurrence of organic and inorganic nitrogen sources influence root uptake by Scots pine seedlings
- 2014
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Ingår i: Tree Physiology. - : Oxford University Press (OUP). - 0829-318X .- 1758-4469. ; 34, s. 205-213
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Tidskriftsartikel (refereegranskat)abstract
- Insights into how the simultaneous presence of organic and inorganic nitrogen (N) forms influences root absorption will help elucidate the relative importance of these N forms for plant nutrition in the field as well as for nursery cultivation of seedlings. Uptake of the individual N forms arginine, ammonium (NH4+) and nitrate (NO3-) was studied in Scots pine (Pinus sylvestris (L.)) seedlings supplied as single N sources and additionally in mixtures of NO3- and NH4+ or NO3- and arginine. Scots pine seedlings displayed a strong preference for NH4+-N and arginine-N as compared with NO3--N. Thus, NO3- uptake was generally low and decreased in the presence of NH4+ in the high-concentration range (500 mu M N), but not in the presence of arginine. Moreover, uptake of NO3- and NH4+ was lower in seedlings displaying a high internal N status as a result of high N pre-treatment, while arginine uptake was high in seedlings with a high internal N status when previously exposed to organic N. These findings may have practical implications for commercial cultivation of conifers.
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| 6. |
- Gärdenäs, Annemieke, et al.
(författare)
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Knowledge gaps in soil carbon and nitrogen interactions - From molecular to global scale
- 2011
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 43, s. 702-717
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this review was to identify, address and rank knowledge gaps in our understanding of five major soil C and N interactions across a range of scales – from molecular to global. The studied five soil C and N interactions are: i) N controls on the soil emissions of greenhouse gases, ii) plant utilisation of organic N, iii) impact of rhizosphere priming on C and N cycling, iv) impact of black N on the stabilisation of soil organic matter (SOM) and v) representation of fractions of SOM in simulation models. We ranked the identified knowledge gaps according to the importance we attached to them for functional descriptions of soil–climate interactions at the global scale, for instance in general circulation models (GCMs). Both the direct and indirect influences on soil–climate interactions were included. We found that the level of understanding declined as the scale increased from molecular to global for four of the five topics. By contrast, the knowledge level for SOM simulation models appeared to be highest when considered at the ecosystem scale. The largest discrepancy between knowledge level and importance was found at the global modelling scale. We concluded that a reliable quantification of greenhouse gas emissions at the ecosystem scale is of utmost importance for improving soil–climate representation in GCMs. We see as key questions the identification of the role of different N species for the temperature sensitivity of SOM decomposition rates and its consequences for plant available N
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| 7. |
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| 8. |
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| 9. |
- Högberg, Mona N, et al.
(författare)
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Quantification of effects of season and nitrogen supply on tree below-ground carbon transfer to ectomycorrhizal fungi and other soil organisms in a boreal pine forest
- 2010
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 187:2, s. 485-493
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Tidskriftsartikel (refereegranskat)abstract
- P>The flux of carbon from tree photosynthesis through roots to ectomycorrhizal (ECM) fungi and other soil organisms is assumed to vary with season and with edaphic factors such as nitrogen availability, but these effects have not been quantified directly in the field. To address this deficiency, we conducted high temporal-resolution tracing of 13C from canopy photosynthesis to different groups of soil organisms in a young boreal Pinus sylvestris forest. There was a 500% higher below-ground allocation of plant C in the late (August) season compared with the early season (June). Labelled C was primarily found in fungal fatty acid biomarkers (and rarely in bacterial biomarkers), and in Collembola, but not in Acari and Enchytraeidae. The production of sporocarps of ECM fungi was totally dependent on allocation of recent photosynthate in the late season. There was no short-term (2 wk) effect of additions of N to the soil, but after 1 yr, there was a 60% reduction of below-ground C allocation to soil biota. Thus, organisms in forest soils, and their roles in ecosystem functions, appear highly sensitive to plant physiological responses to two major aspects of global change: changes in seasonal weather patterns and N eutrophication.
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| 10. |
- 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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