Michael Altgen
Forsker
Sammendrag
Wood has many attractive material qualities, but it is susceptible to biological degradation by wood-decaying fungi. Moisture is one of the critical requirements for wood decay, but much remains unknown about moisture dynamics in decaying wood. To fill this knowledge gap, this study investigated moisture in Scots pine sapwood during decay caused by the brown rot fungus Coniophora puteana. Samples were exposed to decay in two time-series experiments; mass loss and moisture content were recorded over the course of decay, and the bound and free water populations in the samples were analysed using low-field nuclear magnetic resonance (LFNMR) relaxometry in both the decaying state and at full water saturation. Selected samples were also used for water vapour sorption measurements. The time-series decay tests showed that moisture content initially increased due to fungal activity but decreased over time when corrected for mass loss, contrary to the general belief that moisture content increases with decay. LFNMR revealed that bound water content increased on a decayed-mass basis in the decaying state and at saturation, but no increase was seen after correction for mass loss. Free water content followed gravimetric moisture content in the decaying state, but the saturated state measurements revealed an initial increase and subsequent decrease with mass loss. Degradation caused changes in hygroscopicity, but our data show that overall moisture content is regulated by fungal activity rather than by material properties. These findings highlight the complexity of water interactions during fungal degradation, offering valuable new insights into wood degradation mechanisms.
Forfattere
Gry Alfredsen Lone Ross Atle Wehn Hegnes Michael Altgen Andreas Treu Sverre Aarseth Tunstad Igor A. Yakovlev Mari Sand Austigard Johan Mattson Maria Paz Nunez Garcia Anne Cathrine Flyen Cecilie Flyen Trine Mathea Skjeltorp Nanna Bjerregaard PedersenSammendrag
Prosjektet «ArcticAlpineDecay» har undersøkt hvordan klimaendringer og økt menneskelig aktivitet påvirker trebasert kulturarv i arktiske og alpine miljøer, med fokus på Svalbard og Finse. Resultatene viser at lengre perioder med varme og fuktighet gir bedre vekstvilkår for råtesopper og øker risikoen for biologisk nedbrytning. Samtidig forsterker økt ferdsel slitasjen på sårbare kulturmiljøer, særlig på Svalbard hvor mange kulturminner er vanskelige å identifisere og tåler lite påvirkning. Fire faktorer øker risikoen for skader i kulturmiljøene: vanskelig lesbarhet, dårlig teknisk tilstand, spennende detaljer og høy tilgjengelighet. Det er funnet omfattende råte nær bakken, og DNA-analyser viser et stort mangfold av vednedbrytende sopper, inkludert arter som ikke tidligere er dokumentert i polarområder. Alvorlig soppnedbrytning oppstår etter rundt 50 år, noe som betyr at taubanebukker med eldre fundamenter nå er kritisk nært restaureringsbehov. For Finse og Hardangervidda er de største utfordringene økt bruk, manglende kunnskap og fysisk slitasje. Det anbefales økt informasjon til turister og guider, enkel fysisk tilrettelegging, bedre overvåking og kombinasjon av metoder for å avdekke både overflate- og indre råteskader, samt videre forskning.
Sammendrag
This study investigates the moisture-induced recovery of temporary property changes in thermo-mechanically densified (TMD) birch and aspen wood, compared to thermally modified (TM) wood. Both treatments were prepared under identical thermal conditions, differing only by compression in TMD. Dimensional stability, water vapour sorption, and Brinell hardness were assessed before and after repeated wetting and drying cycles to evaluate the effect of stress storage in the polymer matrix and its recovery during moisture exposure. The results indicate that both TMD and TM treatments induce a temporary reduction in moisture uptake, consistent with the formation of an annealed polymer structure. Water saturation and subsequent drying restored higher moisture content and reduced Brinell hardness in TMD wood, highlighting a moisture-driven recovery of the annealed polymer conformation. Notably, the decrease in hardness could not be attributed solely to the reduction in bulk density, indicating additional effects of polymer plasticisation. The presence of compression stresses during TMD appeared to enhance stress storage, thereby influencing the recovery of moisture-induced properties. Initial wood moisture content before TMD had little effect on the temporary reduction in moisture content, suggesting that annealing also occurs in dry states. These findings emphasise the need to account for moisture cycling in TMD wood’s service life. Future work should focus on the interplay between compression stresses and the annealing effect to reduce the temporary nature of the property improvements by TMD.
