VARIATION IN THE COMPOSITION AND CONTENT OF ELLAGITANNINS IN THE HEARTWOOD OF EUROPEAN OAKS (QUERCUS-ROBUR AND Q-PETRAEA) - A COMPARISON OF2 FRENCH FORESTS AND VARIATION WITH HEARTWOOD AGE

The ellagitannin concentration was measured in water extracts of diffe rent heartwood sections of Pressler cores from three Russian and one E nglish Quercus robur tree. As the heartwood age increased, the concent ration of total soluble ellagitannins showed a logarithmic decline, wh ile individual ellagitannins varied in their response. A simple model relating the total soluble ellagitannins and heartwood age was calcula ted. In a second study two heartwood samples were taken from each of 2 0 oak trees (Q robur and Q petraea) from each of two contrasting (Limo usin and Troncais) French forests. Over 70% of the total variation in the concentration of water soluble ellagitannins and total phenolics e xtracted from the samples was attributed to differences between forest s, while relatively little variation occurred between the two within-t ree samples. Lower concentrations were found in more slowly grown timb er from the Troncais forest than in wood from the Limousin region. The different tannin concentrations could not be explained solely by the greater heartwood age of Troncais samples if one assumed that the rate of ellagitannin decline with heartwood age was similar in all trees. A correlation between wood colour, as defined by CIELab colour paramet er hue, colour saturation and b (representing colour along the blue-y ellow axis), and total phenolics and soluble tannins was also observed . The two forests differed in many regards, including environmental co nditions, silvicultural practices and the dominant species.