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-This paper presents results of a semi-quantitative study on the role of Agrilus biguttatus F. in oak decline in Belgium. Larvae of this insect breed in living subcortical tissues of European oak. Several factors favouring attacks are discussed, among which the overall health condition and the local physical and biochemical status of the host tree. Larvae, feeding galleries, pupae, imago and D-shaped emergence-holes of A. biguttatus were observed exclusively in declining and recently dead oaks. Attacks start in the south-facing, sun-exposed parts of the subcrown stem, with a preference for thicker-barked trees or similar areas within declining trees. The feeding of early larval stages induces subcortical necrosis and longitudinal bark cracking. The more destructive tunnelling of advanced larval stages cuts functional vessels and phloem elements, which enhances the decline. In conclusion, effects on wood quality and suitable control options are discussed.

Using data from 20 even-aged and homogeneous mature beech and oak study plots in Flanders (Northern Belgium), an analysis of the empirical relationships between the rates of leaf area index (LAI) change throughout the leaf development of 2008 and stand, site and meteorological variables was performed. Species-specific multiple linear regressions were fitted between the rates of LAI change and the predictors for two distinct periods from April until August. After a sharp increase in LAI following budburst, the seasonal LAI development for both species showed a marked period of stationary LAI development over all study plots. The cause for the cessation of LAI growth was assumed to be the decline of air temperature and radiation during this period. Later on, the rate of LAI development restarted similarly in every plot. The influence of weather on LAI development was high and its effects were different between species, with beech mostly affected by radiation and oak negatively related to minimal and maximal values of air temperature. Furthermore, our analysis suggested that stand structural (tree density and stand basal area for both species) and tree growth characteristics (average tree-ring width ratio for oak) variables were major drivers of the LAI development during early spring. Later during the growth period, stand variables became less predominant in affecting LAI development. Site quality variables affected LAI development to a lesser extent. The seasonal LAI development was found very similar among stands. This study adds a more accurate and comprehensive approach to the modelling of LAI development during leaf growth of two important European temperate deciduous forest species

High-resolution X-ray computed tomography is a promising technique for research on wood cores and will be explored further on other temperate and tropical species. Further study on limba noir is necessary to reveal the causes of density variations and to determine how resistance drillings can be further refined.