| 1. |
- Jönsson Belyazid, Ulrika, et al.
(författare)
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Can Phytophthora quercina have a negative impact on mature pedunculate oaks under field conditions?
- 2006
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Ingår i: Annals of Forest Science. - : EDP Sciences. - 1286-4560 .- 1297-966X. ; 63:7, s. 661-672
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Tidskriftsartikel (refereegranskat)abstract
- Ten oak stands in southern Sweden were investigated to evaluate the impact of the root pathogen Phytophthora quercina on mature oaks under field conditions. Phytophthora quercina was present in five of the stands, while the other five stands were used as controls to verify the effect of the pathogen. In each stand, a healthy, a moderately declining and a severely declining tree were sampled. Fine-root length and nutrient status of each tree were analyzed, and the chemistry of the soil surrounding each tree was determined. The results showed that P. quercina can cause substantial reductions in the fine-root length of mature trees under natural conditions. The impact of the pathogen varied depending on tree vitality and season, being most pronounced for declining trees after an unusually dry summer. Despite the significant reduction in live fine-root length of declining trees in Phytophthora-infested stands, no consistent effects were found on the nutrient status of trees. Based on the significant impact of the pathogen on the fine-root systems of declining trees, we suggest that P. quercina contribute to oak decline in southern Sweden at the sites where it is present. No explanation is currently available for the decline of trees in non-infested stands, but the lack of symptoms of root damage indicate, together with the extensive root growth of declining trees, that root pathogens are not involved in the decline at these sites.
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| 2. |
- Jönsson Belyazid, Ulrika, et al.
(författare)
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Relationships between health of Quercus robur, occurrence of Phytophthora species and site conditions in southern Sweden
- 2005
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Ingår i: Plant Pathology. - : Wiley. - 1365-3059 .- 0032-0862. ; 54:4, s. 502-511
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Tidskriftsartikel (refereegranskat)abstract
- The effect of Phytophthora species, soil chemistry, precipitation and temperature on the vitality of oak was evaluated in 32 oak stands in southern Sweden. In addition, the relationship between the occurrence of Phytophthora species and soil conditions was determined. The results showed that there was a weak association between the presence of P. quercina, the most frequently recovered Phytophthora species in southern Sweden, and the vitality of the oak stands (determined from estimates of crown defoliation of individual trees). The pathogens occurred more frequently in clayey and loamy soils that were less acidic and which had higher base saturation. However, they were found in all but the most acidic soils (pH < 3.5). In stands where Phytophthora species were not present, positive correlations between the average crown defoliation and proportion of damaged trees with average summer precipitation and average annual precipitation were found. There were no significant differences in soil chemistry between healthy and declining stands included in this study, and no significant correlations were found between any soil parameter and crown vitality. Based on the results from these 32 oak stands, it is likely that the decline of oaks in southern Sweden can be attributed to several different site-specific factors, such as infection by P. quercina or unusual weather events, which interact with a number of biotic and abiotic factors, leading to oak decline.
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| 3. |
- Rosengren, Ulrika, et al.
(författare)
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Functional Biodiversity Aspects on the Nutrient Sustainability in Forests–: Importance of Root Distribution
- 2006
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Ingår i: Journal of Sustainable Forestry. - 1054-9811. ; 21:2-3, s. 75-98
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Nutrient availability is of major importance for plant productivity. When estimating long-term sustainability from a nutrient perspective it is therefore interesting to focus on long-term changes in the soil nutrient pools when comparing different forest types. Here, we have highlighted some factors of importance for long term nutrient sustainability (e.g., several forest rotations) and pointed out some important features that differ between forest tree species and also between monocultures and mixed species stands. Using computer models like PROFILE reveals tree rooting depth to be a crucial factor when assessing long-term nutrient sustainability. Literature studies show that soil type and other soil conditions have a strong effect on root distribution. However, Norway spruce is generally a very shallow rooted species, with approximately 80% of it fine roots in the top 20-25 cm, whereas for pendiculate oak, generally 80% of the roots are found down to 60 cm soil depth. Rooting depth of Scots pine and beech seem to be intermediate with 80% of the roots down to approximately 25-30 cm and 30-35 cm, respectively. Importance of mycorrhiza for nutrient uptake in a sustainability perspective is discussed in the paper.
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| 4. |
- Bergmark, Ulrika, et al.
(författare)
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Full of value : improving school learning through the development of an ethical community
- 2008
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Ingår i: The Fifteenth International Conference on Learning.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This workshop presents a school improvement process in an area in Northern Sweden. The shared goal for this school area is to develop and sustain an ethical learning community from pre-schools to secondary schools. In an ethical learning community it is important that children's views and thoughts are listened to and taken seriously. Adults, especially the teachers, have a responsibility to encourage the children to be committed to managing their own learning. Adults bring forward fundamental democratic values, which are discussed with the children. In an ethical community there is an ambition that both children and adults will work and learn together with respect and empathy, in order to enable children to grow as humans. Principals, teachers and children from the school area and also researchers from a local university are involved in this on-going process. Different perspectives on the process will be highlighted in the workshop: a principal's view on the importance of bridging practice in schools together with research for improvement in school and a teacher's view on reflection as a way for development, growth and change. Finally we will present the outcomes so far with children and teachers from this school area.
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| 5. |
- Göransson, Hans, et al.
(författare)
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Estimating the relative nutrient uptake from different soil depths in Quercus robur, Fagus sylvatica and Picea abies
- 2006
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Ingår i: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 286:1-2, s. 87-97
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Tidskriftsartikel (refereegranskat)abstract
- The distribution of fine roots and external ectomycorrhizal mycelium of three species of trees was determined down to a soil depth of 55 cm to estimate the relative nutrient uptake capacity of the trees from different soil layers. In addition, a root bioassay was performed to estimate the nutrient uptake capacity of Rb+ and NH4+ by these fine roots under standardized conditions in the laboratory. The study was performed in monocultures of oak (Quercus robur L.), European beech (Fagus sylvatica L.) and Norway spruce [Picea abies (L.) Karst.] on sandy soil in a tree species trial in Denmark. The distribution of spruce roots was found to be more concentrated to the top layer (0-11 cm) than that of oak and beech roots, and the amount of external ectomycorrhizal mycelia was correlated to the distribution of the roots. The uptake rate of [86 Rb+] by oak roots declined with soil depth, while that of beech or spruce roots was not influenced by soil depth. In modelling the nutrient sustainability of forest soils, the utilization of nutrient resources in deep soil layers has been found to be a key factor. The present study shows that the more shallow-rooted spruce can have a similar capacity to take up nutrients from deeper soil layers than the more deeply rooted oak. The distribution of roots and mycelia may therefore not be a reliable parameter for describing nutrient uptake capacity by tree roots at different soil depths.
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| 6. |
- Göransson, Hans, et al.
(författare)
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Nutrient acquisition from different soil depths by pedunculate oak
- 2006
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Ingår i: Trees. - : Springer Science and Business Media LLC. - 1432-2285 .- 0931-1890. ; 20:3, s. 292-298
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Tidskriftsartikel (refereegranskat)abstract
- Eight oak trees (Quercus robur L.) received P-32 at a soil depth of 50 cm and P-33 at a soil depth of 15 cm at the end of June 2002 through plastic tubes inserted into the mineral soil. The phosphorus uptake from different soil depths was estimated by analysing the concentration of P-32 and P-33 in the foliage of oak growing in a mixed stand in southern Sweden. P-32 and P-33 were recovered in the leaves/needles after 21 and 39 days. The recovery of labelled P in oak was higher from 15 cm soil depth than from 50 cm, however, more than 4% of the total amount of labelled P was taken up from 50 cm. This indicates that oak can utilize deep soil layers for nutrient uptake. A study on the uptake of Cs (as an analogue to K) and N-15 into the leaves was performed on the same trees and detectable amounts of N-15 and Cs were recovered in leaves and buds. This indicates that N-15 and Cs can be used to study nutrient uptake of mature trees from the mineral soil.
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| 7. |
- Krus, Ulrika, et al.
(författare)
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Anaplerosis via pyruvate carboxylase is required for the fuel-induced rise in the ATP:ADP ratio in rat pancreatic islets.
- 2006
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 1432-0428 .- 0012-186X. ; 49:7, s. 1578-1586
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Tidskriftsartikel (refereegranskat)abstract
- AIMS/HYPOTHESIS: The molecular mechanisms of insulin release are only partially known. Among putative factors for coupling glucose metabolism to insulin secretion, anaplerosis has lately received strong support. The anaplerotic enzyme pyruvate carboxylase is highly expressed in beta cells, and anaplerosis influences insulin secretion in beta cells. By inhibiting pyruvate carboxylase in rat islets, we aimed to clarify the hitherto unknown metabolic events underlying anaplerotic regulation of insulin secretion. METHODS: Phenylacetic acid (5 mmol/l) was used to inhibit pyruvate carboxylase in isolated rat islets, which were then assessed for insulin secretion, fuel oxidation, ATP:ADP ratio, respiration, mitochondrial membrane potential, exocytosis and ATP-sensitive K(+) channel (K(ATP)-channel) conductance. RESULTS: We found that the glucose-provoked rise in ATP:ADP ratio was suppressed by inhibition of pyruvate carboxylase. In contrast, fuel oxidation, respiration and mitochondrial membrane potential, as well as Ca(2+)-induced exocytosis and K(ATP)-channel conductance in single cells, were unaffected. Insulin secretion induced by alpha-ketoisocaproic acid was suppressed, whereas methyl-succinate-stimulated secretion remained unchanged. Perifusion of rat islets revealed that inhibition of anaplerosis decreased both the second phase of insulin secretion, during which K(ATP)-independent actions of fuel secretagogues are operational, as well as the first and K(ATP)-dependent phase. CONCLUSIONS/INTERPRETATION: Our results are consistent with the concept that anaplerosis via pyruvate carboxylase determines pyruvate cycling, which has previously been shown to correlate with glucose responsiveness in clonal beta cells. These processes, controlled by pyruvate carboxylase, seem crucial for generation of an appropriate ATP:ADP ratio, which may regulate both phases of fuel-induced insulin secretion.
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| 8. |
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| 9. |
- Snygg-Martin, Ulrika, 1965, et al.
(författare)
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Cerebrovascular complications in patients with left-sided infective endocarditis are common: a prospective study using magnetic resonance imaging and neurochemical brain damage markers.
- 2008
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Ingår i: Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. - : Oxford University Press (OUP). - 1537-6591. ; 47:1, s. 23-30
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Tidskriftsartikel (refereegranskat)abstract
- Background. @nbsp; Cerebrovascular complications (CVCs) have remained a major therapeutic and prognostic challenge associated with infective endocarditis, and definite risk factors have not been fully elucidated. This prospective study was designed to the evaluate the total incidence of CVC associated with infective endocarditis and major risk factors. Methods. @nbsp; During 2 study periods, from June 1998 through April 2001 and from September 2002 through January 2005, patients were prospectively enrolled in the study regardless of neurological symptoms. Study patients underwent neurological examinations and magnetic resonance imaging of the brain, and cerebrospinal fluid analyses of inflammatory and neurochemical markers of brain damage (neurofilament protein and glial fibrillary acidic protein) were performed. Results. @nbsp; Sixty patients who experienced episodes of left-sided infective endocarditis were evaluated; 35% of these patients experienced a symptomatic CVC. Silent cerebral complications were detected in another 30% of the patients, and the total CVC rate was 65% (95% confidence interval, 58%-72%). Five percent of patients experienced their first neurological symptom after the initiation of antibiotic treatment without prior surgery. No new symptomatic CVCs were detected after 10 days of antibiotic treatment. No neurological deterioration was observed after surgery in patients who were established to have a symptomatic CVC preoperatively. A larger heart valvular vegetation size was a risk factor for both symptomatic and silent CVCs; Staphylococcus aureus etiology conferred a higher risk for symptomatic cerebral complication only. Conclusions. @nbsp; The use of sensitive methods of detection indicates that the incidence of CVC associated with infective endocarditis is high, but the risk for neurological deterioration during cardiac surgery after a CVC is lower than previously assumed. The major mechanism behind cerebral complications associated with infective endocarditis is cerebral embolization, although the dominant neurological symptoms vary considerably.
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| 10. |
- Wallander, Håkan, et al.
(författare)
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Ectomycorrhizal fungal biomass in roots and uptake of P from apatite by Pinus sylvestris seedlings growing in forest soil with and without wood ash amendment
- 2005
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Ingår i: Mycorrhiza. - : Springer Science and Business Media LLC. - 1432-1890 .- 0940-6360. ; 15:2, s. 143-148
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Tidskriftsartikel (refereegranskat)abstract
- Forest soil from an experimental Norway spruce forest with four levels of wood ash addition (0, 1, 3 and 6 tonnes ha(-1)) was used to inoculate pine (Pinus sylvestris) seedlings with indigenous ectomycorrhizal (EM) fungi. Uptake of P-32 and Rb-86 in a root bioassay was used to estimate the demand for P and K by seedlings grown in the different soils. Utilisation of P from apatite was tested in a laboratory system where uptake by the ectomycorrhizal mycelium was separated from uptake by roots. The demand for P and K in the seedlings was similar regardless of the ash treatment. Variation in EM levels, estimated as fungal biomass (ergosterol) in roots, was large in the different soils, but not related to ash addition. Uptake of P from apatite was, on average, 23% of total seedling P and was not related to EM levels. It was concluded that the improved P uptake from apatite by EM fungi found in earlier studies is probably not a general phenomenon among EM fungi. The small effect of ash addition on EM levels and P uptake suggests that addition of granulated wood ash is a forest management treatment that will have only minor influence on ectomycorrhizal symbiosis.
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