Jørund Johansen
Research Scientist
(+47) 994 93 343
jorund.johansen@nibio.no
Place
Bergen
Visiting address
Thormøhlensgate 55, 5006 Bergen
Authors
Fride Høistad Schei Mie Prik Arnberg John-Arvid Grytnes Maren Stien Johansen Jørund Johansen Anna Birgitte Milford Anders Røynstrand Mari Mette TollefsrudAbstract
Climate change and human activities have accelerated the spread of non-native species, including forest pests and pathogens, significantly contributing to global biodiversity loss. Pathogens pose a significant threat to forest ecosystems due to a lack of coevolution with native hosts, resulting in ineffective defence mechanisms and severe consequences for the affected tree species. Ash dieback, caused by the fungus Hymenoscyphus fraxineus, is a relatively new invasive forest pathogen threatening ash (Fraxinus excelsior) with mortality rates in northern Europe reaching up to 80 %. The loss of ash due to dieback has severe ecological implications, potentially leading to an extinction cascade as ash provides crucial habitats and resources for many organisms. Despite this, the consequences of ash dieback on associated communities are largely unknown. To address this, we analysed changes in species richness, vegetation structure, and composition in 82 permanent vegetation plots across 23 Norwegian woodlands. We compared data collected before and 10–14 years after the emergence of ash dieback. In these woodlands, ash significantly declined in cover, leading to changes in tree species composition and facilitating the establishment of other woody tree species like hazel (Corylus avellana) and the invasive species sycamore (Acer pseudoplatanus). Despite these changes in the tree species composition, no significant alterations were observed in the understory plant community, indicating a degree of ecosystem resilience or a lagging community response. At this point, and with our focus on the vascular plants, we do not find support for cascading effects due to ash dieback. However, our findings demonstrate that one invasive species is facilitating the expansion of another, raising concerns about potential ecological imbalance and cascading effects in the future.
Abstract
No abstract has been registered
Abstract
Pollarding in agroforestry systems was traditionally an important practice for fodder acquisition in Western Norway, as well as in many other parts of the world. The practice has long been in decline, but to maintain cultural landscapes and biodiversity enhancement from pollarding, farmers now receive a public grant for each tree they pollard. In this interdisciplinary study we investigate which ecosystem services modern pollarding practices provide, under the influence of the current pollarding policy. We have performed both in-depth interviews and a quantitative survey targeting all pollarding farmers in the county of Vestland in Western Norway. We find that bioresources obtained from the branches from pollarding are to some extent still taken into use, mainly in the form of tree fodder for farm animals and firewood, but a lot of the branches remain unused. Biodiversity benefits are obtained from preserving old trees that often are located on agricultural land as solitary trees, as these trees provide important habitats, particularly for species growing on the bark, such as lichens and mosses, or within the decaying wood, such as, for example, fungi and insects. The modern practice of letting branches rot in the field provide habitats for insects and hence additional benefits to biodiversity. For the farmers, the main motivations to pollard are the cultural, aesthetic and historical values of pollarded trees. They see few disadvantages with pollarding, and most of them plan to continue in the future. The grant provides an incentive for pollarding, but our results indicate that the practice would continue without it, although less than now, especially with the establishment of new pollards.
