A CORRELATION STUDY OF DENDROMETER BAND DATA AND PHENOLOGICAL EVENTS WITH DIRECT TREE RING WIDTH MEASUREMENTS IN SOME TROPICAL TREES OF SRI LANKA.

Abstract

Dendrometers provide an easy and a reliable method of detecting growth patterns of trees by measuring changes in the diameters of tree trunks.

A total of 163 trees were used in this study selected from 15 forest stations in the lowlands of Sri Lanka. In addition to the increase in circumference at breast height, other phenological events such as periods of leaf growth/ greening, flowering, seed ripening and fruiting were observed. The measured diameter increments were used for calculation of the number of growth periods as well as to calculate the periods of highest growth and their relationships with the observed phenological events. A correlation study was carried out with observed ring width measurements in tree cores obtained using a Swedish increment borer and wood slices. An important feature that emerged from this study was the similarities and differences among growth periods in the different tree species investigated as well as the differences in the duration of the growth periods.

For example in the case of Swietenia macrophylla and Dipterocarpus spp the growth periods extended throughout the year with only a few months of less vigorous growth, whereas in trees such as Macaranga digyana, the growth period was confined to only a few months of the year. Trees such as Palaquium rubiginosum and Tectona grandis showed only one prominent growth period for the year while most other tree species showed 2-3 growth periods. In Horsfieldia irya the maximum growth period corresponded with the period of initiation of flowering whereas in almost all tree species, the minimum growth corresponded with phenological events such as flowering. Trees within different climatic regimes such as thick dense forest and open woodlands responded differently.

It can be confidently assumed in tree-ring chronology the observed phenological events are important in growth patterns and give important hints with reference to ring numbers in trees under tropical conditions which observations are substantiated in this study through direct ring width and ring number establishment in cores and slices obtained from trees of known age.