Volkmar Timmermann
Research Scientist
Abstract
Alm (Ulmus glabra) er en nøkkelart i norske edelløvskoger og klassifisert som sterkt truet (EN), hovedsakelig på grunn av almesyke og beiteskader fra hjortedyr. Arten har høy økologisk verdi fordi den fungerer som vert for et stort antall tilknyttede arter, inkludert mange rødlistearter. Bevaring av alm er derfor viktig både for biologisk mangfold og for kulturhistoriske landskap, særlig i områder med tradisjonell styving. Almesyke (Dutch elm disease, DED) er den mest destruktive sykdommen som har rammet løvtrær i Europa i moderne tid. Sykdommen er en vaskulær soppsykdom på almetrær, forårsaket av sopper i slekten Ophiostoma, der Ophiostoma novo-ulmi i dag er den mest aggressive og epidemiologisk dominerende arten i Europa. Sykdommen spres hovedsakelig via barkbiller i slekten Scolytus, men kan også spres gjennom rotkontakter mellom nabotrær og via menneskelig transport. I Norge var sykdommen lenge begrenset til Oslofjordområdet, men nye funn fra 2020–2024 viser en klar geografisk ekspansjon, blant annet til Sørlandet og Vestland. Denne rapporten oppsummerer historiske erfaringer, aktuell biologisk kunnskap og dagens situasjon i Vestland, og gir faglige anbefalinger for videre forvaltning og risikoreduserende tiltak.
Authors
Lena Wohlgemuth Mathieu Jonard Andreas Schmitz Paul Schmidt-Walter Heleen Deroo Peter Waldner Nathalie Cools Bruno De Vos Arne Verstraeten Inken Krüger Anne Thimonier Volkmar Timmermann Mathias Neumann Pasi Rautio Kai SchwärzelAbstract
Key message A large European forest monitoring dataset reveals a pattern of reduced foliar nitrogen (N) and phosphorus (P) concentrations following drought conditions in spruce and pine, and, in the case of P, beech and oak, often exhibiting N:P imbalances. Gradual nutritional imbalance and nutrient deficiency during droughts raise concern for tree vitality and forest carbon sequestration under climate change. Context Nitrogen (N) and phosphorus (P) are essential nutrients for tree metabolism, forest growth, and carbon sequestration, yet the drivers of their availability to trees are often complex to untangle. Aims and methods In this study, we investigated environmental controls of foliar N, P, and N:P based on > 4100 N and P measurements in foliage samples of main tree species (beech, oak, spruce, and pine) across 279 European monitoring sites by applying mixed regression models. Results We found overall nutritional declines over the past three decades that ranged from − 1.8% to − 2.7% and from − 3.5% to − 4.2% per 10 years for foliar N and P concentrations respectively. At around two-thirds of monitoring sites, where foliar N:P significantly increased over the examined time span, these increases were dominated by declines in foliar P. Foliar sampling years with summer droughts (standardized precipitation evapotranspiration index < − 1.2) were associated with lower standardized foliar P concentrations in all tree species compared to average years. Conclusion We concluded that variations in drought conditions drive foliar N and P on a short-term, mostly annual basis, while throughfall deposition of N impacted foliar N over larger time spans of several decades depending on tree species.
Authors
Thomas M. Mansfield Artin Zarsav Filipa Cox Laura M. Suz Martin I. Bidartondo Sietse van der Linde Nadia Barsoum Colin Averill Alan Kuo Leho Tedersoo Pasi Rautio Arthur Gessler Bruno De Vos Luc Croisé Henning Meesenburg Markus Wagner Frank Jacob Paweł Lech Anna Kowalska Martin Greve Genoveva Popova Beat Frey Marcus Schaub Marco Ferretti Peter Waldner Vicent Calatayud Roberto Canullo Giancarlo Papitto Aleksander Marinšek Lars Vesterdal Morten Ingerslev Helge Meissner Volkmar Timmermann Nadine Eickenscheidt Andreas Schmitz Francis M. Martin Joseph Spatafora Peter G. Kennedy Annegret Kohler Jonathan M. Plett Ian C. Anderson Sara Branco Igor V. Grigoriev Chris J. Pires Sarah A. Unruh Lawrence W. Zettler Otto Miettinen Ilya Viner Tom W. May Teresa Lebel David E. A. Catcheside Pamela S. Catcheside Helen P. Vonow Leigh A. Burgoyne Julia Haska Mark A. AnthonyAbstract
Ectomycorrhizal fungi (EMF) produce mycelia with variable extension and complexity, which can be classified according to soil ‘exploration types’ (ETs). ETs have received attention as one of the few mycorrhizal trait frameworks, but without an empirical classification of ET functional diversity and environmental preferences, understanding and interpreting EMF biogeographic patterns has been difficult. We conducted a synthesis combining: comparative EMF genomics to describe functional divergence in decomposition and nutrient cycling genes across ETs; and EMF trait distribution modeling across continental Europe, pairing soil and root EMF surveys to establish biogeographic ET niche profiles. We demonstrate a signature of ETs encoded in EMF genomes, which is independent from phylogeny and linked to biomass production strategies. EMF ET relative abundances were separated by soil, root, and dominant tree leaf type habitats and exhibited unique correlations with forest biotic (e.g. plant productivity and plant pathogen densities) and abiotic (e.g. nitrogen deposition and soil pH) conditions. These findings support a theory that EMF niche partitioning can be partially explained by extraradical mycelial traits, with underlying variation in ET biogeography likely arising from distinct decomposition and nutrient cycling potentials. We also identify important limitations to this trait framework and provide a guided outlook for future research.
