| 1. |
- Bengtson, Per, et al.
(författare)
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Relieving substrate limitation-soil moisture and temperature determine gross N transformation rates
- 2005
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 111:1, s. 81-90
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Tidskriftsartikel (refereegranskat)abstract
- A field experiment was designed with the objective to reveal the interactions between soil moisture, temperature, total, dissolved, and phosphate buffer extractable C and N, and microbial activity in the control of in situ gross N mineralization and immobilization rates in a deciduous forest. We had three alternative hypotheses to explain variations of the gross N transformations: 1) microorganisms are C limited, 2) microorganisms are N limited, or 3) neither C nor N limit the microorganisms but moisture and temperature conditions. Each hypothesis had specific criteria to be fulfilled for its acceptance. The results demonstrated that gross N transformation rates were more dependent on and variable with soil moisture and temperature than the size of the different C and N pools. The immobilization of N was dependent on the gross mineralization rate, suggesting that the production of enzymes for mineralization of organic N and the immobilization of N from the surrounding soil is disconfirmed when the intracellular N content of the microorganisms is sufficiently high. If the microorganisms are starved for N, enzyme systems involved in both the assimilation and mineralization of N are activated. The mean in situ gross N mineralization rate was two orders of magnitude higher than the natural N deposition in the area and the N addition in the NITREX experiments, meaning that a reduction in the gross N mineralization rate of about 1% would be enough to compensate for the addition of inorganic N. This decrease would hardly be detectable given the great spatial and temporal variability of N transformation rates.
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| 2. |
- Bengtson, Per, et al.
(författare)
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Spatial distributions of plants and gross N transformation rates in a forest soil
- 2006
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Ingår i: Journal of Ecology. - : Wiley. - 1365-2745 .- 0022-0477. ; 94:4, s. 754-764
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- 1 This work demonstrates that spatial distribution of understorey vegetation and gross N transformation rates in a mixed beach-oak forest is closely correlated within a distance of a few metres. The findings imply that plant diversity and productivity have a major influence on gross rates of N transformation and vice versa. 2 A geostatistical analysis was used to evaluate the spatial relationships between abundance and species composition of the understorey vegetation and in situ gross N mineralization, NH4+ immobolization and nitrification rates. 3 The gross N transformation rates and the plants spatial variation were correlated within the forest, but plant distribution was more dependent on the fraction of mineralized N that was nitrified than on individual N transformation rates. 4 The total cover of the understorey vegetation varied more in space than the species composition, and was higher in areas with high N transformation rates. 5 Plant species benefiting from high net nitrification rates were more common in areas with a low activity of mineralizing and nitrifying microorganisms, possibly because the net and gross rates were independent of each other. In fact, those species occurred most often in areas in which a large fraction of mineralized N was nitrified. 6 Beech and oak trees also had an effect on the spatial variation of the understorey vegetation. Beech trees provided conditions more suitable for plants benefiting from NO3-, whereas the vascular plant cover was greater under oak trees, probably in response to a higher light interception than under beech trees. 7 Oak generally had a positive impact on gross N transformation rates compared with beech, perhaps reflecting differences in litter quality and climate caused by the two species. 8 The influence of trees alone could not explain the full magnitude of the variation of N transformation rates or the presence of overlapping areas with high mineralization and immobilization rates. These were probably caused by other factors, such as soil moisture content. 9 This work sheds new light on the small-scale spatial links between above-ground plant diversity and abundance, and below-ground microbial N transformations.
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| 3. |
- D'Hertefeldt, Tina, et al.
(författare)
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Extensive physiological integration in Carex arenaria and Carex disticha in relation to potassium and water availability
- 2002
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Ingår i: New Phytologist. - Chichester : Wiley. - 1469-8137 .- 0028-646X. ; 156:3, s. 469-477
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Tidskriftsartikel (refereegranskat)abstract
- Physiological integration between ramets is beneficial when acquiring heterogeneously distributed resources, and is hypothesized to occur when the benefits of resource sharing outweigh the costs. Our aim was to investigate if resource availability affected physiological integration in Carex arenaria and Carex disticha. Ramet systems were grown in high potassium and high water (K+ W+), high K and low water (K+ W-), or low K and high water (K- W+) for 1 month. Thereafter, water and K transport were traced with erythrosin and rubidium, respectively. Carex arenaria and C. disticha transported erythrosin over seven ramet generations and rubidium throughout the whole ramet system, but C. arenaria exported 20% more rubidium from the labelled shoot than C. disticha. A detailed analysis of subset of plants suggested that C. disticha in low K abundance shared more rubidium than in high K abundance, and that C. arenaria ramets in both K+ W- and K- W+ shared more resources than K+ W+ ramets. We demonstrated long-distance resource transport for K and water in C. arenaria and C. disticha. The distance of integration was not affected by resource availability in C. arenaria or C. disticha, but local concentrations of K showed marked and contrasting responses to nutrient and water treatment in both species.
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| 4. |
- D'Hertefeldt, Tina, et al.
(författare)
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Responses to mineral nutrient availability and heterogeneity in physiologically integrated sedges from contrasting habitats.
- 2011
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Ingår i: Plant Biology. - Chichester : Wiley. - 1438-8677 .- 1435-8603. ; 13:3, s. 483-492
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Tidskriftsartikel (refereegranskat)abstract
- Clonal plants from poor habitats benefit less from morphologically plastic responses to heterogeneity than plants from more productive sites. In addition, physiological integration has been suggested to either increase or decrease the foraging efficiency of clonal plants. We tested the capacity for biomass production and morphological response in two closely related, rhizomatous species from habitats that differ in resource availability, Carex arenaria (from poor sand dunes) and C. disticha (from nutrient-richer, moister habitats). We expected lower total biomass production and reduced morphological plasticity in C. arenaria, and that both species would produce more ramets in high nutrient patches, either in response to signals transported through physiological integration, or by locally determined responses to nutrient availability. To investigate mineral nutrient heterogeneity, plants were grown in boxes divided into two compartments with homogeneous or heterogeneous supply of high (H) or low (L) nutrient levels, resulting in four treatments, H-H, H-L, L-H and L-L. Both C. arenaria and C. disticha produced similar biomass in high nutrient treatments. C. disticha responded to high nutrients by increased biomass production and branching of the young parts and by altering root:shoot ratio and rhizome lengths, while C. arenaria showed localised responses to high nutrients in terms of local biomass and branch production in high nutrient patches. The results demonstrated that although it has a conservative morphology, C. arenaria responded to nutrient heterogeneity through morphological plasticity. An analysis of costs and benefits of integration on biomass production showed that young ramets of both species benefited significantly from physiological integration, but no corresponding costs were found. This suggests that plants from resource-poor but dynamic habitats like sand dunes respond morphologically to high nutrient patches. The two species responded to nutrient heterogeneity in different traits, and this is discussed in terms of local and distant signalling of plant status.
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| 5. |
- Diekmann, M, et al.
(författare)
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Prediction of species response to atmospheric nitrogen deposition by means of ecological measures and life history traits
- 2002
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Ingår i: Journal of Ecology. - : Wiley. - 1365-2745 .- 0022-0477. ; 90:1, s. 108-120
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Tidskriftsartikel (refereegranskat)abstract
- 1 The main objective of this study was to predict the responses of vascular plant species to atmospheric nitrogen deposition and enhanced soil nitrogen levels. The study was carried out in deciduous forests located in three regions of southern Sweden. The abundance of vascular plants, as well as soil pH and nitrogen mineralization rates, were studied in a total of 661 sample plots. 2 We calculated an ecological measure (N-dev value) for all species based on their observed vs. expected nitrification ratios at a given soil pH, and compared its accuracy in predicting abundance changes with results using life history traits. Data from long-term field studies and fertilization experiments were used for validation. 3 N-dev values were positively correlated between neighbouring regions. Values for the southernmost region (Skane) were also positively related to the changes in species frequency observed in large-scale flora surveys and permanent plot studies in that area and with species changes reported from Central Europe. Values from one of two other regions were also consistent. N-dev values from Skane (but no other region) predicted species responses in short-term fertilization experiments. 4 No life history trait was as good a predictor as N-dev, although plant height, leaf anatomy, leaf nitrogen concentration and phenology showed significant correlations. Attributes related to taxonomy, life form, relative growth rate and habitat type showed no agreement with the changes in species abundance. 5 We predict that species with the following attribute syndrome will increase in abundance in response to enhanced nitrogen levels: those favoured by a high soil nitrification ratio relative to other species at a given soil pH, tall stature, hydro- to helomorph anatomy, high leaf nitrogen concentration and a late phenological development.
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| 6. |
- Faarinen, Mikko, et al.
(författare)
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Al-26 at the AMS facility in Lund
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 223-24, s. 130-134
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Tidskriftsartikel (refereegranskat)abstract
- To broaden the AMS programme in Lund by including Al studies, a new injector has been installed and tested at the 3 MV Pelletron accelerator. Detailed optical calculations have been performed to obtain maximum mass and energy resolution. The design of the injector, the improvement in the resolution compared to the old injector, as well as preliminary tests with a Al-26-beam, are presented. By using accelerator mass spectrometry (AMS) to measure the long-lived aluminium isotope Al-26 it has become possible to study the uptake, distribution and retention of aluminium in biological system under physiologically realistic conditions. Results from a pilot project on Al-26 in wheat plants are presented.
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| 7. |
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| 8. |
- Falkengren-Grerup, Ursula, et al.
(författare)
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Förändras floran av kvävenedfallet?
- 2000
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Ingår i: Effekter av kvävenedfall på skogsekosystem. - 9162050664
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Abstract is not available
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| 9. |
- Falkengren-Grerup, Ursula, et al.
(författare)
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Land use effects on soil N, P, C and pH persist over 40-80 years of forest growth on agricultural soils
- 2006
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 1872-7042 .- 0378-1127. ; 225:1-3, s. 74-81
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Tidskriftsartikel (refereegranskat)abstract
- Previous cultivation may have long-lasting effects on oak forests, e.g., nitrogen (N) and carbon (C) depletion, phosphorus (P) enrichment and lowered soil acidity, which may influence soil processes, wood production and plant diversity. We used a large database on land use to sample 18 sites where oak had been planted 40-80 years ago on continuously forested land and formerly cultivated fields that had similar soil properties before the different land uses. We estimated the 'total' pools of N, P and C and 'available' fractions of N and P at three soil depths. The soil data were compared with element concentrations in leaves of four plant species. Soil solution concentration of nitrate at 50-60 cm was used as an estimate of nitrate leaching. Total N and mineralisable N in the soil were higher in the continuously forested land than in the formerly cultivated fields and this was reflected in the N concentration in Dryopteris filix-mas. Total P and available P tended to be lower in the continuously forested land than in the formerly cultivated fields which were reflected in the P concentrations in Dryopteris and Quercus robur Soil C was higher and pH was lower in the continuously forested land than in the formerly cultivated fields. Leaching of NO3--N started to appear in higher concentrations below pH 4.5 and the leaching is interpreted more as a pH than a land use effect. Aluminium (At) concentrations were higher in Dryopteris and Quercus and the iron (Fe) concentration in Milium effusum. while calcium (Ca) was lower in all plant species. Potassium (K) was lower in Stellaria holostea and no difference was found for the magnesium (Mg) concentration in plants. As previous land use seems to affect soil nutrients and potentially toxic elements it is important to identify the limiting factors for the different ecosystem components to be able to manage the forests correctly. It is probable that areas with significant N deposition are not N-limited even in the N-depleted formerly cultivated fields and that a higher P content and soil pH there may result in higher biomass production and changes in plant diversity. The risk of nitrate leaching in the most acidic, continuously forested land must also be taken into consideration in the management of forests.
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| 10. |
- Falkengren-Grerup, Ursula, et al.
(författare)
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Plant nitrate use in deciduous woodland: the relationship between leaf N, N-15 natural abundance of forbs and soil N mineralisation
- 2004
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 36:11, s. 1885-1891
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Tidskriftsartikel (refereegranskat)abstract
- Our aim was to study whether the in situ natural abundance N-15 (delta(15)N)-values and N concentration of understory plants were correlated with the form and amount of mineral N available in the soil. Also to determine whether such differences were related to earlier demonstrations of differences in biomass increase in the same species exposed to nutrient solutions with both NO3- and NH4+ or to NH4+ alone. Several studies show that the delta(15)N of NO3- in soil solution generally is isotopically lighter than the delta(15)N of NH4+ due to fractionation during nitrification. Hence, it is reasonable to assume that plant species benefiting from NO3- in ecosystems without significant NO3- leaching or denitrification have lower delta(15)N-values in their tissues than species growing equally well, or better, on NH4+. We studied the delta(15)N of six 4 understory species in oak woodlands in southern Sweden at 12 sites which varied fivefold in potential net N mineralisation rate (minNH(4)(+) + NO3-). The species decreased in benefit from NO3- in the following order: Geum urbanum, Aegopodium podagraria, Milium effusum, Convallaria majalis, Deschampsia flexuosa and Poa nemoralis. Four or five species demonstrated a negative correlation between minNO(3)(-) and leaf delta(15)N and a positive correlation between minNO(3)(-) and leaf N concentration. In wide contrast, only D. flexuosa, which grows on soils with little nitrification, showed a positive correlation between minNH(4)(+) and the leaf N concentration and delta(15)N-value. Furthermore, delta(15)N of plants from the field and previously obtained indices of hydroponic growth on NH4+ relative to NH4+ + NO3- were closely correlated at the species level. We conclude that delta(15)N may serve as a comparative index of uptake of NO3- among understory species, preferably in combination with other indices of N availability. The use of 5 15 N needs careful consideration of known restrictions of method, soils and plants.
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