The Effects of Some Internal and External Factors on Growth Rate of Lovoa Trichilioides Deduced from its Wood Anatomy

Abstract

In Lovoa trichilioides Harms (African Walnut) trees grown in the Nigerian swampy lowland rainforest, the growth rings are clearly visible and annual; the termination of each ring can be distinguished by a zone of thicker walled fibres and a narrow band of parenchymatous cells. The areas of the growth rings were computed from the ring widths and the radius of the pith of each disc. Variation in ring width between the sample plots was not significant. Between-tree variation in ring width within the sample plots was very highly significant with a variance component (V.C.) of 6.1 per cent. It is likely that part of the between-tree variation was genetic because the trees within plots were of the same age, planted at the same spacing and grown under uniform environment. The effect of distance above the ground on ring width was significant with a V.C. of 3.6 per cent. The average width of the outer five growth rings increased steadily up the tree from 3.4 to 4.7 mm. The effect of the interaction of trees and distances above the ground was very highly significant; V.C. = 14.2 per cent. The effect of cardinal direction on ring width was not significant. The age effect on ring width was very highly significant; V.C. = 40.0 per cent. Ring width decreased considerably with age from 13.2 mm in the first year to 1.5 mm in the 11 th year. Regression analysis showed that up to 91 per cent of the variation in ring width was determined by corresponding variation in age. The interaction effect of trees and ages was very highly significant; V.C. = 8.1 per cent. Ring area increased with age up to a point and then decreased steadily with age. For the quadratic model, up {o 96 per cent of the variation in ring area was explained by variation in age. Ring width and ring area were neither strongly related to crown diameter nor crown per cent.