Comparing results to identify defects in wood of Norway spruce (Picea abies L. Karst.) using the drill devices Resistograph 1410, Teredo and Impulshammer-sound system IML. II. Drill diagrams on red-rot wood and discussion

Faulty fee and red rot damaged spruce discs (Fig. 1, 7) were checked for wood conditions by different diagnosis methods -IML sound ranger system, IML-Resistograph 1410 and Teredosystem (Technologiepark Clausthal Management GmbH, Germany). Radial sound velocities on faulty free discs (Tab. 1) were higher (between 930 m/s and 1013 m/s) than on red rot damaged discs (between 601 m/s and 880 m/s). Therefore an assessing of a damage is limited possible using the sound system (Fig. 14). But due to the bark and sapwood damages caused by the thick screws of the sound system and the relatively poor information about the width and form of the wood damages it must be emphazised that the relative expensive device is only limited useable for wood diagnosis. The drilling curves of Teredo and Resistograph along the same measuring line of spruce wood ale very similar; they show rots and hollows through low drilling resistances. Both devices are suitable for tree diagnosis (Fig. 3a, b, 4, 8 to 10). The expensive Resistograph 1410 ist excellently suitable for recording the wood conditions along a 40 cm long drill channal if special disadvantages and some experience are involved. The device convinced through its high and exact resolution to detect the borders between early and late wood of wide ring wood (Fig. 13). But it was impossible to identify all the exact ring number in older trees with narrow ring width. Therefore the device is suited for practical use of tree specialists within tree care and wood diagnosis but for scientific research the use is limited. The relative cheap Teredo system with conical drill heads is also suitable for checking wood resistances by using the moving forward drill curves. On lower level recording moving backward curves can be falsified by systematic errors. Therefore these curves should not be involved in wood resistance interpretations.