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Durability-based designs with timber require reliable information about the wood properties and how they affect its performance under variable exposure conditions. This study aimed at utilizing a material resistance model (Part 2 of this publication) based on a dose–response approach for predicting the relative decay rates in above-ground situations. Laboratory and field test data were, for the first time, surveyed globally and used to determine material-specific resistance dose values, which were correlated to decay rates. In addition, laboratory indicators were used to adapt the material resistance model to in-ground exposure. The relationship between decay rates in-and above-ground, the predictive power of laboratory indicators to predict such decay rates, and a method for implementing both in a service life prediction tool, were established based on 195 hardwoods, 29 softwoods, 19 modified timbers, and 41 preservative-treated timbers.

Service life planning with timber requires reliable models for quantifying the effects of exposure-related parameters and the material-inherent resistance of wood against biotic agents. The Meyer-Veltrup model was the first attempt to account for inherent protective properties and the wetting ability of wood to quantify resistance of wood in a quantitative manner. Based on test data on brown, white, and soft rot as well as moisture dynamics, the decay rates of different untreated wood species were predicted relative to the reference species of Norway spruce (Picea abies). The present study aimed to validate and optimize the resistance model for a wider range of wood species including very durable species, thermally and chemically modified wood, and preservative treated wood. The general model structure was shown to also be suitable for highly durable materials, but previously defined maximum thresholds had to be adjusted (i.e., maximum values of factors accounting for wetting ability and inherent protective properties) to 18 instead of 5 compared to Norway spruce. As expected, both the enlarged span in durability and the use of numerous and partly very divergent data sources (i.e., test methods, test locations, and types of data presentation) led to a decrease in the predictive power of the model compared to the original. In addition to the need to enlarge the database quantity and improve its quality, in particular for treated wood, it might be advantageous to use separate models for untreated and treated wood as long as the effect of additional impact variables (e.g., treatment quality) can be accounted for. Nevertheless, the adapted Meyer-Veltrup model will serve as an instrument to quantify material resistance for a wide range of wood-based materials as an input for comprehensive service life prediction software.

A round robin involving 15 European participants was set up in 2006. The round robin consists of both a field test according to the double layer test method and a laboratory test with two different preconditioning methods. When comparing EN 84 preconditioning (two weeks water leaching) with natural preconditioning (1 year in field, above ground) according to CEN/TS 15397, no significant difference could be noted for untreated controls, thermally modified wood or CCA impregnated wood. However, for wood treated with a metal-free organic preservative, a clear difference could be seen where much of the efficacy seen after EN 84 preconditioning is lost when natural preconditioning is used instead. In the field tests, the control pine performs similar in all fields whereas both thermally modified and preservative treated wood performs much better in the Nordic fields than in the mid- and southern European fields. The thermally modified wood performs almost as poor as the controls in the Southern European fields, whereas the organic preservative treated wood performs well in these fields. In the six mid-European fields, the organic preservative treated and thermally modified wood performs equally poor but much better than the controls. The best compliance between field performance and laboratory test results is obtained when comparing the average results from the field tests with results from EN 113 tests with Poria placenta after natural preconditioning according to CEN/TS 15397.

Elektroniskā versija nesatur pielikumus, Promocijas darbā „Koksnes brūnā trupe: bazīdijsēnes un to destruktīvā iedarbība uz lignocelulozi” pētīta koksnes trupes sēņu izplatība un daudzveidība Latvijas mežu biotopos, kā arī Latvijas un Maķedonijas celtniecības koksnē. Laboratorijas apstākļos ar ķīmiskām un fizikālām metodēm pētīts brūnās trupes sēņu izraisītās koksnes degradācijas mehānisms, lai, pamatojoties uz ķīmisko komponentu un struktūras izmaiņām, raksturotu šī procesa dinamiku. Latvijas mežu biotopos atrastas 144 koksnes trupes sēņu sugas (Basidiomycota). No tām 14 sugas ir retas, bet 22 trupes sēnes Latvijā ir reģistrētas pirmo reizi. Vislielākais sēņu skaits un pirmo reizi reģistrēto sugu skaits tika atrasts dabas liegumu teritorijās. 16% no reģistrēto sugu skaita pieder brūnās trupes sēnēm, pārējās (84%) - baltās trupes sēnēm. Latvijas celtniecības koksnē pēc izplatības biežuma izteikti dominēja brūnās trupes sēnes (86% gadījumu), bet Maķedonijas kultūrvēstures pieminekļos - baltās trupes sēnes (84% gadījumu), kas saistāms ar skujkoku materiālu tradicionālu izmantošanu Latvijas celtnēs, un lapkoku izmantošanu Maķedonijas celtnēs. Visbiežāk sastopamā brūnās trupes sēne Latvijas celtniecības koksnē ir Serpula lacrymans, kas konstatēta 56% gadījumu, kamēr Maķedonijas celtnēs šī sēne līdz šim nav atrasta. S. lacrymans dabā nav konstatēta ne Latvijā, ne Maķedonijā. Mūsu eksperimentos izmantoto koksnes paraugu degradācijas mehānisma izpēte deva iespēju raksturot un nodalīt trīs posmus koksnes brūnās trupes procesā: agrīnā, pamatstadija un noslēguma stadija. Agrīnā stadija (6-10 dienas) ir kritiskais posms, kurā traheīdu lumeni ir inficēti ar sēnes hifām, notiek lignīna oksidatīva modifikācija un relatīvās koncentrācijas pieaugums uz polisaharīdu sašķelšanas rēķina, celulozes polimerizācijas pakāpes strauja samazināšanās, hemiceluložu glikomannānu noārdīšana, bet masas zudumi vēl nav novērojami. Pamatstadijā (20 - 90 dienas) notiek modificētā lignīna repolimerizācija, jaunu mikroporu veidošanās, hemiceluložu acetātgrupu noārdīšana, polisaharīdu degradācijas produktu patēriņš, ko raksturo pieaugoši koksnes masas zudumi. Noslēguma stadiju (> 90 dienas) raksturo koksnes šūnas sekundārās sienas plaša degradācija ar lieliem masas zudumiem. Degradācijas agrīnajā stadijā uz koksnes šūnu, acīmredzot, vispirms iedarbojas sēņu veidotie ekstracelulārie reaktīvie skābekļa savienojumi (RSS), bet vēlāk, pamata un noslēguma stadijās, notiek enzimātiska koksnes šūnas noārdīšana. Bojātu koksnes šūnu ķīmisko un fizikālo analīžu rezultāti atklāja atšķirības starp brūnās trupes sēnēm, kas acīmredzot saistāmas ar sēņu celulolītisko un/ vai ligninolītisko sistēmu īpatnībām un to iedarbību uz koksnes šūnas komponentiem. Pētījuma rezultāti ir praktiski izmantojami koksnes aizsardzībā, parādot, ka nepieciešams atrast veidu, kā inhibēt sēņu izdalītos RSS, piemēram, paaugstinot koksnes pH, vai izmantojot savienojumus ar antioksidantu īpašībām, vai kavējot RSS reakcijas ar koksnē esošajiem dzelzs joniem. Darba rezultāti izmantoti degradācijas procesu izpētes metožu izstrādei un jaunu koksnes aizsardzības līdzekļu efektivitātes pārbaudei. Darbs ir uzrakstīts latviešu valodā. Darba 120 lappušu apjomu veido: ievads, literatūras apskats, kopsavilkums, darba mērķis un uzdevumi, eksperimentālā daļa, rezultāti un diskusija, secinājumi, aizstāvāmās tēzes, literatūras saraksts un pielikums. Darbā ir iekļauti 43 attēli, 12 tabulas un 123 literatūras avoti. Darbs izstrādāts no 1998. līdz 2008. gadam Latvijas Valsts Koksnes ķīmijas institūtā sadarbībā ar Latvijas Universitāti, Latvijas Dabas muzeju, Maķedonijas Sv. Kirila un Metodija Universitāti, Igaunijas Ķīmiskās fizikas un biofizikas institūtu, Tallinas Tehnisko universitāti un Vācijas Federālo mežsaimniecības un koksnes pētījumu centru., In the Doctoral theses “Wood Brown-Rot: Basidiomycetes and their Destructive Action on Lignocellulose”, the prevalence and diversity of wood-rot fungi in Latvian forest biotopes as well as Latvian and Macedonian construction wood was investigated. In laboratory conditions, applying chemical and physical methods, the wood degradation mechanism caused by brown-rot fungi was investigated so that, based on the changes in the chemical components and structure, to characterise the dynamics of this process. In Latvian forest biotopes, 144 species of wood-rot fungi (Basidiomycota) were found. From them, 14 species are rare, while 22 species are registered for the first time in Latvia. The greatest number of fungi and the number of the species registered for the first time are found in the territories of natural restricted areas. 16% of the registered species pertains to brown-rot fungi, while the rest of them (84%) belong to white-rot fungi. In Latvian construction wood, in terms of prevalence, brown-rot fungi dominate markedly (86% cases), while, in Macedonian cultural monuments, white-rot fungi prevail (84% cases), which is connected with the traditional use of coniferous wood materials in Latvian buildings and the use of deciduous wood in Macedonian buildings. The most commonly occurring brown-rot fungus in Latvian construction wood is Serpula lacrymans, which is found in 56% cases, while this fungus has not yet been found in Macedonian buildings. In nature, S. lacrymans is found neither in Latvia nor in Macedonia. The study of the mechanism of degradation of the wood samples used in our experiments made it possible to characterise and separate three stages in the wood brown-rot process: early stage, basic stage and final stage. The early stage (6-10 days) is a critical one, in which tracheid lumens are infected with fungal hyphae, lignin oxidative modification, and the relative increase in concentration at the expense of polysaccharides cleavage, a dramatic decrease in the cellulose polymerisation degree, and the degradation of hemicellulose glucomannanes occur, while mass losses are not yet observed. At the basic stage (20-90 days) repolymerisation of the modified lignin, formation of new micropores, degradation of hemicellulose acetate groups, and consumption of polysaccharide degradation products occur, which is characterised by the increasing wood mass losses. The final stage (> 90 days) is characterised by the extensive degradation of the wood cell secondary wall with great mass losses. At the early stage of degradation, the wood cells are obviously firstly influenced by the reactive oxygen species (ROS) that are formed by the fungi, while later, at the basic and final stages, enzymatic degradation of wood cells occurs. The results of the chemical and physical analysis of the damaged wood cells have revealed distinctions among the brown-rot fungi, which is obviously connected with the peculiarities of the cellulolytic and/or ligninolytic systems and their action on wood cell components. The results of the studies are practically applicable in wood protection, indicating that it is necessary to find a way to inhibit the ROS released by the fungi, for example, by increasing the wood pH or using compounds with antioxidant properties or hampering the ROS reactions with the iron ions present in wood. The results of the work are used to develop methods for investigating degradation processes and testing of efficiency of new wood preservatives. The work is written in Latvian. The 120 page volume of the work is comprised by the introduction, literature survey, summary, the work’s objective and tasks, experimental, results and discussion, conclusions, defended theses, references and annex. The work includes 43 figures, 12 tables and 123 references. The work has been developed from 1998 to 2008 at the Latvian State Institute of Wood Chemistry in cooperation with the Univers