Variability of radial growth in cork oak adult trees under cork production

The radial growth of mature cork oak trees (Quercus suber L.) was studied for 9 years, between two consecutive cork harvests, by measuring monthly diameter stem growth with dendrometers in southwestern Portugal. The average tree annual diameter increment was 0.95 cm per year but significant inter-annual growth differences were observed. Diameter increments were higher in the year following the cork harvest (1.44 cm), and decreased more or less regularly until the end of the cycle (0.41 cm). Smaller annual diameter increments could be related to climatic factors such as drought periods with low winter rainfall. Tree growth was seasonal with radial growth in March-November and dormancy in November-February. On average, the radial growth rate attains a maximum value in June-July and decreases sharply in summer. The growth pattern and seasonality were very similar in all trees and independent of the tree diameter. The results obtained may be used as background information in management systems for cork oak stands, i.e. for optimizing the duration of cork production cycle in relation to the thickness of cork planks, the timing of cork extraction and the development of growth curves. (C) 2002 Published by Elsevier Science B.V.