Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2016
Abstract
There is an increasing awareness of how the aesthetical performance of wood exposed outdoors changes over time and especially in the first few years after installation. Mould and blue stain fungi are biological agents that contribute to the weather grey colour on a wooden façade, and the blue stain fungi Aureobasidium pullulans is commonly identified as colonizer on coated and uncoated wood exposed outdoors. In this study 21 wood substrates (untreated, preservative treated and modified) were tested for their susceptibility to A. pullulans when incubated at three different temperatures (11, 16 and 22°C). Western red cedar and preservative treated wood had the lowest mould ratings at the end of the test period (84 days). Alder, ash, Norway spruce and Sitka spruce reached maximum rating already at day 28, and at day 84 also aspen, European larch, thermally modified pine, birch, acetylated pine and DMDHEU modified pine had reached maximum rating. Incubation temperature had a significant influence on the growth of A. pullulans throughout the test period for acetylated and DMDHEU modified samples – and generally the modified wood substrates were more sensitive to changes in temperature than the other tested substrates. Scots pine sapwood seemed to be less susceptible to A. pullulans in mono cultures, demonstrating low mould ratings throughout the test period. This contradicts to previous studies were Scots pine sapwood tended to have high susceptibility when using a mix of mould and blue stain fungi.
Authors
Lone Ross Thomas Kringlebotn Thiis Geir Isak Vestøl Ingunn Burud Solrun Karlsen Lie Olav Albert HøibøAbstract
Use of uncoated wood in building façades has increased the last years, and therefore it is important to understand and control the aesthetical character and appearance of wood materials used outdoors. By predicting the aesthetical service life and the visual appearance of a wooden façade over time, we can accommodate some of the end-user expectations, perception, values and aesthetical preferences. The spatial variation of climate on a façade is large, and estimation of the weathering process and mould growth on outdoor exposed wood should be based on the actual surface climate rather than data from meteorological stations. A first version of a simulation model that aims to predict and visualize future aesthetical appearance of wooden façades has been developed. The model is based on existing mould growth models and on a new model for surface meteorological conditions that account for RH, temperature and UV. The on-set of mould growth on selected wood materials (pine, spruce, larch, oak, aspen, thermally treated pine) have been studied in 8 different controlled climate conditions, where two levels of surface condensation regimes have been mimicked to capture time-of-wetness. Wood samples in conditions with high RH (85%) and longest time-of-wetness had the earliest on-set of mould growth, and under these conditions temperature (25°C/10°C) had no significant impact. Generally aspen had the earliest on-set of mould growth and thermally treated pine the latest. Data on on-set of mould growth will be incorporated in the simulation model to enable a knowledge-based decision tool regarding design and material selection.
Authors
Guro BrodalAbstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
Fusarium and Microdochium may cause seedling blight and poor germination of cereal seeds. However, indications of poor survival of Fusarium in seed and improved germination after some months of storage have been observed. A study was carried out to investigate if seed storage can contribute to improved seed quality. Samples from seed lots of barley, oats and spring wheat were tested for germination capacity and Fusarium /Microdochium infection frequencies a few days after harvest, and after 5, 12 and 15 months of storage. In barley, the average germination percentage increased slightly, from 92% at harvest to 95% after five months of storage. In oats, the average germination percentage increased from 82% to 85% during the first five months. In spring wheat, the average germination percentage was reduced from 81% at harvest to 67% after five months. In barley and oats, average Fusarium /Microdochium frequencies were reduced during storage, with the highest reduction observed during the first five months (from 50% to 37%, and from 60% to 46%, barley and oats respectively). In spring wheat, no significant reduction in average infection level was recorded (58% at harvest, 50% after 15 months of storage). There was however, variation between seed lots in all three cereal species in both germination percentage and Fusarium /Microdochium frequencies during the storage period. It is concluded that storage of barley and oats seeds for 5 months after harvest may in some cases increase the seed quality and thereby meet the certification requirements of minimum 85% germination.
Abstract
No abstract has been registered
Abstract
Convergent Cross Mapping (CCM) has recently been introduced by Sugihara et al. for the identification and quantification of causal relationships among ecosystem variables. In particular, the method allows to decide on the direction of causality; in some cases, the causality might be bidirectional, indicating a network structure. We extend this approach by introducing a method of surrogate data to obtain confidence intervals for CCM results. We then apply this method to time series from stream water chemistry. Specifically, we analyze a set of eight dissolved major ions from three different catchments belonging to the hydrological monitoring system at the Bramke valley in the Harz Mountains, Germany. Our results demonstrate the potentials and limits of CCM as a monitoring instrument in forestry and hydrology or as a tool to identify processes in ecosystem research. While some networks of causally linked ions can be associated with simple physical and chemical processes, other results illustrate peculiarities of the three studied catchments, which are explained in the context of their special history.
Authors
Nicholas ClarkeAbstract
No abstract has been registered
Abstract
Aphids in cereals are an important problem in Europe. Entomopathogenic fungi in the Phylum Entomophthoromycota are among their natural enemies. Under certain conditions, they can cause epizootic events and control pest aphid populations. This epizootic development is affected by many abiotic and biotic factors such as aphid species and their host plant (including weeds within the crop), fungal species and isolates, and temperature. Studies from Denmark, UK, Slovakia and suggest that the genus Pandora is the most prevalent fungal pathogen of the English grain aphid (Sitobion avenae). Which fungal species that is the most prevalent in populations of the other important aphid species in cereals in Europe, the Bird cherry-oat aphid (Rhopalosiphum padi), is less clear. We chose, however, to use Pandora to assess the biological control potential of Entomophthoromycota against aphids in cereals and to produce data that might be used in a pest-warning model incorporating the effect of this natural enemy. This was done by conducting laboratory studies on the virulence of two Pandora isolates (collected in the same field) on R. padi and Myzus persicae at three temperatures (12, 15 and 18◦C). M. persicae is a polyphagous aphid that may be present on weeds. It can be an alternative host for Pandora and hence might also affect the epidemic development of Pandora in aphids that are cereal pests. Our preliminary results show that R. padi is more resistant to the tested Pandora isolates than M. persicae. The two Pandora isolates had different virulence in the two aphid species tested. The temperature did not influence the virulence.
Abstract
The two-spotted spider mite, Tetranychus urticae, is a serious pest of numerous crops worldwide. Sustainable management solutions for T. urticae include predators and entomopathogens. Neozygites floridana is a naturally occurring obligate fungal pathogen of T. urticae and can cause declines in T. urticae populations. The purpose of this study was to determine whether releasing the predatory mite Phytoseiulus persimilis into T. urticae populations has the potential to increase transmission of N. floridana and accelerate the development of an epizootic. This is the first study quantifying the effect of P. persimilis on transmission of N. floridana to T. urticae in a controlled microcosm study. Our results show that introducing P. persimilis into T. urticae, populations increased the proportion of T. urticae infected with N. floridana. By the final sampling occasion, the number of T. urticae in the treatment with both the predator and the pathogen had declined to zero in both experiments, while in the fungus-only treatment T. urticae populations still persisted. We suggest that releasing P. persimilis into crops in which N. floridana is naturally present has the potential to improve spider mite control more than through predation alone.