A new method called HF-densitometry is introduced, which measures relative density variations along wood surfaces utilizing the dielectric properties ofwood. The method is based on the propagation of continuous electromagnetic waves in a high-frequency (HF) transmitter-receiver link of an extremely small electrode system, which is in direct contact with the wood surface investigated. The electromagnetic field emitted by the transmitting electrode propagates through a small volume of the wood sampie to the receiving electrode, located very close to the transmitting electrode. The received signal strength is directly influenced by the dielectric properties of the material along the propagation path. The variation of the relative dielectric constant in different wood structures is correlated with the density variations in a way the received signal strength increases with increasing wood density. The dielectric measuring device, developed on the basis of the new method, allows non-destructive, extremely fast measurements of wood density variations . The new HF-densitometry method was compared to X-ray densitometry by performing measurements on an identical spruce sampie.

A new method for the preparation of wood samples for high-resolution reflected-light microscopy in combination with a species-specific image analysis system is introduced. The method is based on an ultraprecise single-point diamond flycutter equipped with air bearings and functions on the basis of a rotating diamond edge. Extensive and very smooth surfaces can be produced on increment cores as well as entire cross sections. Hence, this technique provides the prerequisites for a continuous microscopic analysis across large tree-ring sequences, or entire cross sections. Patching or sub-sectioning is not required. The high-resolution analysis of cell structures of spruce and oak presented here introduces new approaches for describing and predicting reactions of diameter growth to various environmental events.

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