Lawal, A. and Oyewusi, E.O.

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Genetic information of trees is stored as a sequence of four bases or nucleotides. This genetic information or genotype of trees does not normally change throughout their life time. Observed differences in any trait of interest among individual trees may be due to the differences in genes coding for that trait or variation in environmental conditions. In many cases, it is a combination of the differences in genes coding for the trait and variation in environmental conditions. This research investigated the disparity in growth traits in a teak plantation with the intention to finding out the cause of such growth dissimilarity and harnessing such potential for plus tree selection and subsequent teak plantation improvement. The study was carried out in a private teak plantation located at Itaogbolu, Ondo state. The plantation was established in the year 2000. The one hectare plantation was divided into 25m x 25m plots and four (4) plots were randomly selected using random number generation. All trees within each sample plot were inventorized i.e. diameter at the base, breast height, middle, top and height were measured using relaskop and girth diameter tape. Trees in each plot were grouped into three (3) different height classes namely: Upper Height Class "UHC" (Height >15m), Middle Height Class "MHC" (height between 10m and 15m) and Lowest Height Class "LHC" (height < 10m). Trees under each height class were identified and tagged. In each class, nine (9) trees were selected randomly to uncover the disparity in their height trait. Soil samples were collected at 0-20cm, 20-40cm and 40-60cm depths from three points around each of the selected trees using soil auger. Soil samples from the same depth were bulked to form a composite sample. These composite soil samples were labeled accordingly and taking to the laboratory for analysis. The results indicated that 5.73% of the trees in the plantation were in the ≤10m height class, 53.05% of them were found within 10-15m height class whiled 41.22% of the trees were found in ≥15m height class. Soil characteristics where individual tree under different height classes were growing in this plantation were not significantly different. Hence the difference in growth traits, particularly tree height, observed in this Tectona grandis plantation was not as a result of the variation in soil characteristics but may be attributed to the differences in the genetic make-up of the trees. It is therefore recommended that seed collection should be done carefully from the tallest mother trees particularly if the objective of establishing the plantation is pole or timber production.. Key words: Genetic make-up, Soil characteristics, Teak plantation, Height Trait