Water absorption and desorption in Norway spruce and its influence on durability

Sammanfattning: The durability of wood is a complex problem dependent on many variables, but especially the presence of excessive amounts of water in wood causes many problems. First of all, fungi that cause rot need water to live and propagate. Water also affects dimensional change through shrinking and swelling, which in turn influence crack formation and wood strength. Consequently, wood that naturally has low water-absorption ability should be desirable for outdoor use The main objective of this work was to find parameters that affect liquid water absorption and desorption in end grain of Norway spruce (Picea abies (L.) Karst). Focus has been on liquid water absorption in end grain because most damage occurs in the end grain on products exposed outdoors. In order to investigate this problem, computed tomography (CT) scanning and image processing and multivariate statistics have been used. To ascertain whether the differences in water absorption and desorption measured with CT scanning correspond to differences in microbiological activity and cracking, a field test was performed. For this study, 30 spruces were selected from three sites. The strategy for the selection of test trees was to obtain as large differences as possible between parameters that could be expected to control water distribution in the tree, such as crown size, density, age and access to water.