In de jaren dertig van de vorige eeuw hebben de houtvesters Jansen en Blokhuis, geïnspireerd door Duits voorbeeld, gemengde bosopstanden aangelegd in Drenthe. Een veranderend klimaat stimuleert beheerders tegenwoordig ook om weer te denken aan het aanleggen van gemengde bossen. Meer mengen betekent vaak ook het introduceren van ‘nieuwe soorten’. Maar wat zou je dan introduceren? De gewone zilverspar (Abies alba) is zo’n voor Nederland ‘nieuwe soort’ met potentie. Dit concluderen Chris Hartman en Stefan Poelman in hun afstudeeronderzoek aan de hogeschool Van Hall Larenstein. Zij verkenden de rol die de gewone zilverspar kan gaan spelen in de bossen van de toekomst. Dankzij Jansen en Blokhuis hebben we in Drenthe gemengde bossen waarin de gewone zilverspar al bijna 100 jaar staat. De ervaringen die daar zijn opgedaan geven een doorkijkje naar de toekomst.
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Numerous medical studies have shown the positive effects of forests on different aspects of human health. This study deals with the content of major terpenes in dominant coniferous species in Tara National Park, Serbia, in order to explore the potential for the development of a novel health tourism programme based on forest therapy. Main terpenes were analysed using a headspace-sam-pling technique coupled with gas-chromatography-mass spectrometry (Head-space-GC/MS). Nee-dles of fir and spruce growing in the vicinity of hiking trails were investigated for possibilities to perform such therapy. Major detected terpenes were α-cadinol and spathulenol previously de-scribed as antiviral, antitumor, antimicrobial and immunomodulatory agents. The results of the study were favourable and worked well with the existing walking infrastructure in the observed area of the Tara Mountain, as they act as invaluable resources for designing the structured forest bathing walks. The study not only adds to the knowledge in the environmental and public health realm but also to tourism and sustainability studies.
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Recent research has indicated an increase in the likelihood and impact of tree failure. The potential for trees to fail relates to various biomechanical and physical factors. Strikingly, there seems to be an absence of tree risk assessment methods supported by observations, despite an increasing availability of variables and parameters measured by scientists, arborists and practitioners. Current urban tree risk assessments vary due to differences in experience, training, and personal opinions of assessors. This stresses the need for a more objective method to assess the hazardousness of urban trees. The aim of this study is to provide an overview of factors that influence tree failure including stem failure, root failure and branch failure. A systematic literature review according to the PRISMA guidelines has been performed in databases, supported by backward referencing: 161 articles were reviewed revealing 142 different factors which influenced tree failure. A meta-analysis of effect sizes and p-values was executed on those factors which were associated directly with any type of tree failure. Bayes Factor was calculated to assess the likelihood that the selected factors appear in case of tree failure. Publication bias was analysed visually by funnel plots and results by regression tests. The results provide evidence that the factors Height and Stem weight positively relate to stem failure, followed by Age, DBH, DBH squared times H, and Cubed DBH (DBH3) and Tree weight. Stem weight and Tree weight were found to relate positively to root failure. For branch failure no relating factors were found. We recommend that arborists collect further data on these factors. From this review it can further be concluded that there is no commonly shared understanding, model or function available that considers all factors which can explain the different types of tree failure. This complicates risk estimations that include the failure potential of urban trees.
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