Hybrid aspen is a crossbreed between European and North American aspen. It is a fast growing tree species that has shown strong growth in the South of Sweden. The follow-ups that have been made on hybrid aspen stands, have mainly been done on plant material in the South of Sweden. In the North of Sweden, only occasional studies have been made, and the knowledge of Northern hybrid aspen stands is, thus, unsatisfactory. In the South of Norrland, land owners have planted hybrid aspen, but what kind of plants it is, and how well these stands have established, is not ascertained, since data has not been compiled on the subject. The objective of this study is to evaluate practical plantations of hybrid aspen in the South of Norrland regarding height growth, survival and damages. The ambition is to increase the knowledge about practical plantations regarding height growth, survival and damages, and from the conclusions thereof, give recommendations for future establishments of hybrid aspen in the area. For the study, eight hybrid aspen stands in the South of Norrland were localised. Inventories were made of the stands, the land owners were interviewed and the material was compiled and analysed. Annual height growth varied amongst the stands between 0,4 and 1 meter and was in average 0,6 meter. Survival varied between 41 and 100 percent, with a mean value of 70 percent. The proportion of damaged stems varied between 0 and 85 percent, with a mean value of the stands of 27 percent. Plant mortality was explained by the land owners to be a result of field-mouse damages, which is confirmed by earlier research. The examined hybrid aspen stands in the South of Norrland demonstrate varying results in terms of height growth, survival and damages, but mainly a result that makes the tree species interesting as an alternative to traditional tree species. / Hybridasp är en korsning mellan europeisk och nordamerikansk asp. Det är ett snabbväxande trädslag som har påvisat god tillväxt i södra Sverige. De uppföljningar som har gjorts på hybridaspbestånd har främst varit på plantmaterial i södra Sverige. I norra Sverige har det endast gjorts enstaka undersökningar och kunskapen om de nordliga hybridaspbestånden är därför bristfällig. I södra Norrland har markägare planterat hybridasp, men vilket plantmaterial det är och hur dessa bestånd har etablerat sig, är i dagsläget osäkert då det inte finns någon sammanställd data över detta Undersökningens syfte är att utvärdera praktiska planteringar av hybridasp i södra Norrland avseende höjdtillväxt, överlevnad och skador. Målet är att öka kunskapen om praktiska planteringar avseende höjdtillväxt, överlevnad och skador och utifrån slutsatser av detta ge rekommendationer för framtida etableringar av hybridasp i området. För studien lokaliserades åtta hybridaspbestånd i södra Norrland. Bestånden inventerades, markägarna intervjuades och materialet sammanställdes och analyserades. Höjdtillväxten per år varierade i bestånden mellan 0,4 och 1,1 meter och var i medeltal 0,6 meter. Överlevnaden varierade mellan 41 och 100 procent med ett medelvärde på 70. Andel skadade stammar varierade mellan 0 och 85 procent med ett medelvärde för bestånden på 27 procent. Avgångarna förklaras av markägarna till största del beror på sorkskador, vilket tidigare forskning styrker. Undersökta hybridaspbestånd i södra Norrland påvisar varierande resultat vad gäller höjdtillväxt, överlevnad och skador men överlag ett resultat som gör trädslaget intressant som alternativ till de traditionella trädslagen.

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Wood is a complex material and the mechanical properties are influencedby a number of structural parameters. The objective of this study has been toinvestigate the relationship between the structure and the mechanical propertiesof hardwood. Two levels were of special interest, viz. the cellular structureand morphology of the wood, and the ultra-structure of the cell wall. In thenext step, it was of interest to examine how the mechanical properties ofhardwood change with spontaneous/induced changes in morphology and/orchemical composition beyond the natural variation found in nature. Together, this constituted the framework and basis for two larger projects,one on European aspen (Populus tremula) and hybrid aspen (Populus tremulax Populus tremuloides), and one on European oak (Quercus robur). Amethodology was developed where the concept of relative density and compositemechanics rules served as two useful tools to assess the properties ofthe cell wall. Tensile testing in the longitudinal direction was combined withchemical examination of the material. This approach made it possible to revealthe mechanical role of the lignin in the cell wall of transgenic aspen trees,and investigate the consequences of holocellulose degradation in archaeologicaloak from the Vasa ship. The study on transgenic aspen showed that a major reduction in lignin inPopulus leads to a small but significant reduction in the longitudinal stiffness.The longitudinal tensile strength was not reduced. The results are explainableby the fact that the load-bearing cellulose in the transgenic aspen retained itscrystallinity, aggregate size, microfibril angle, and absolute content per unitvolume. The results can contribute to the ongoing task of investigating andpinpointing the precise function of lignin in the cell wall of trees. The mechanical property study on Vasa oak showed that the longitudinaltensile strength is severely reduced in several regions of the ship, andthat the reduction correlates with reduced average molecular weight of theholocellulose. This could not have been foreseen without a thorough mechanicaland chemical investigation, since the Vasa wood (with exception fromthe bacterially degraded surface regions) is morphologically intact and witha micro-structure comparable to that of recent oak. The results can be usedin the ongoing task of mapping the condition of the Vasa wood. / QC 20110420