FALSE RING OCCURRENCES AND THEIR IDENTIFICATION IN TEAK (Tectona grandis) IN NORTH-EASTERN THAILAND

The objectives of this research were to identify and locate the position of false ring occurrences in natural teak (Tectona grandis) and to relate their formation to local climate variability. Vessel diameters were measured and standardised from pith towards the bark in order to identify false rings and define annual ring boundaries. Two types of false rings were classified as false ring type I and II in earlywood and latewood respectively. False ring type I had one or more rows of axial parenchyma associated with large vessels at the beginning of the annual ring. False ring type II was divided into two groups based on their characteristics. The first group had an aggregation of large vessels associated with paratracheal parenchyma while the second group did not have any paratracheal parenchyma. The occurrences of false rings could be explained by the fluctuations of rainfall and temperature during the growing season. False ring type I occurred during drought following heavy rainfall at the beginning of the monsoon period. After dense fibre occurrences in latewood, heavy rainfall and warm temperature at the end of the monsoon period re-stimulated large vessels and/or parenchymatous cells to form false ring type II.