| 1. |
- Bakys, Remigijus, et al.
(författare)
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Occurrence and pathogenicity of fungi in necrotic and non-symptomatic shoots of declining common ash (Fraxinus excelsior) in Sweden
- 2009
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Ingår i: European Journal of Forest Research. - : Springer Science and Business Media LLC. - 1612-4669 .- 1612-4677. ; 128, s. 51-60
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Tidskriftsartikel (refereegranskat)abstract
- Currently, massive dieback of Fraxinus excelsior is observed in countries of eastern, northern and central Europe, and the reasons for it are unclear. The aims of the present work were (a) to study fungal communities in declining F. excelsior crowns; (b) to clarify role of fungi in the decline. Shoots from symptomatic crowns were collected in four localities in central Sweden, and distributed into the following categories: (a) visually healthy; (b) initial necroses; (c) advanced necroses; (c) dead tops. The most frequently isolated fungi were Gibberella avenacea, Alternaria alternata, Epicoccum nigrum, Botryosphaeria stevensii, Valsa sp., Lewia sp., Aureobasidium pullulans and Phomopsis sp., and these taxa were consistently found in shoots of all four symptomatic categories. Forty-eight taxa of other fungi were isolated, and fungal diversity was not exhausted by the sampling effort. The same taxa of fungi were dominant in F. excelsior shoots of different symptomatic categories, and moderate to high similarity of fungal communities was observed in shoots despite the symptoms. Forty-four isolates from 24 fungal taxa were used for artificial inoculations of 277 1-year-old F. excelsior seedlings in bare root nursery. After 2 years, only four fungi caused symptomatic necroses of bark and cambium: A. alternata, E. nigrum, Chalara fraxinea and Phomopsis sp. The most pathogenic was C. fraxinea, inducing symptoms on 50% of inoculated trees, while three other fungi caused necroses on 3-17% of inoculated trees. Infection biology of C. fraxinea and environmental factors determining susceptibility of F. excelsior to decline deserve future investigations.
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| 2. |
- Mellander, Per-Erik, et al.
(författare)
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Recovery of photosynthetic capacity in Scots pine : a model analysis of forest plots with manipulated winter/spring soil temperature regimes.
- 2008
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Ingår i: European Journal of Forest Research. - : Springer Science and Business Media LLC. - 1612-4669 .- 1612-4677. ; 127:1, s. 71-79
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Tidskriftsartikel (refereegranskat)abstract
- Both aboveground and belowground climate affects net primary production (NNP) and forest growth. Little is known about how above and belowground factors interact. The BIOMASS-model was tested to simulate photosynthetic recovery over a wide range of soil temperatures created by snow cover manipulations on tree-scale plots in a 20-year-old Scots pine stand in northern Sweden. The differences in timing of soil warming between the plots covered a span of two months. Carbon assimilation in needles, sap flow, needle water potential and climatic parameters were measured in the field. The simulations revealed that an early start of soil warming gave a relatively early photosynthetic recovery and a 7.5% increase of NPP. Late soil warming delayed the photosynthetic recovery and reduced the NPP by 13.7%. This indicated that soil temperature needed to be accounted for, as well as air temperature, when analysing photosynthetic recovery and NPP in boreal environment. The effects of differences in soil temperature were reflected in the simulated photosynthetic recovery. The model did not fully capture the delay of photosynthetic recovery caused by a late soil warming. It was possible to integrate the complexity of the soil climate effects into a threshold date for soil thaw, using sapflow measurements together with information about air temperature and a day degree sum, as long as water availability was not limiting water uptake by roots. Although a more realistic mechanism than that currently in BIOMASS is desirable as climate change shifts the typical patterns of interplay between air and soil temperature dynamics.
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| 3. |
- Papageorgiou, Aristotelis C., et al.
(författare)
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Genetic variation of beech (Fagus sylvatica L.) in Rodopi (NE Greece)
- 2008
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Ingår i: European Journal of Forest Research. - : Springer. - 1612-4669 .- 1612-4677. ; 127:1, s. 81-88
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Tidskriftsartikel (refereegranskat)abstract
- The recent taxonomic classification of beech in Europe considers existence of one species (Fagus sylvatica L.) with two subspecies: F. sylvatica ssp. sylvatica and F. sylvatica ssp. orientalis. Four beech populations growing on the Greek part of the Rodopi Mountains were studied using morphological traits as well as DNA molecular markers (AFLPs and chloroplast DNA SSR). The aim of the study was to describe the variation patterns of beech in the Rodopi Mountains and to test the hypothesis of possible introgression between the beech subspecies' sylvatica and orientalis in this area. Both morphological traits and gene markers revealed a possible influence of F. orientalis on the east side of Rodopi and at the low elevations, while characters resembling F. sylvatica were observed mainly on the western part of the mountains and in higher altitudes. There was a clinal increase of genetic diversity from the west to the east, reaching a level firstly reported for beech populations. These results can be explained either by the existence of a main refugial area for beech during the last glaciation or by the occurrence of a recent hybridization among the subspecies, which were spatially isolated during the last glaciation and came into reproductive contact during their postglacial remigration. These two scenarios are not necessarily mutually exclusive.
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| 4. |
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| 5. |
- Sandberg, Karin, et al.
(författare)
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Separating Norway spruce heartwood and sapwood in dried condition with near-infrared spectroscopy and multivariate data analysis
- 2009
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Ingår i: European Journal of Forest Research. - : Springer Science and Business Media LLC. - 1612-4669 .- 1612-4677. ; 128:5, s. 475-481
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Tidskriftsartikel (refereegranskat)abstract
- Norway spruce [Picea abies (L.) Karst.] heartwood and sapwood have differing wood properties, but are similar in appearance. An investigation was made to see whether near-infrared spectroscopy (NIRS) could be used with multivariate statistics for separation between heartwood and sapwood in dry state on tangential longitudinal surfaces. For classification of wood into sapwood and heartwood, partial least square (PLS) regression was used. Orthogonal signal correction (OSC) filtering was used on the spectra. This study shows that a separation of sapwood and heartwood of spruce is possible with NIR spectra measured in a laboratory environment. The visible-wavelength spectra have significant influence on the predictive power of separation models between sapwood and heartwood of spruce. All 44 specimens in the calibration set were correctly classified into heartwood and sapwood. Validation of the model was done with a prediction set of 16 specimens, of which one was classified incorrectly.
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