No abstract

Growth periodicity was followed for two consecutive annual cycles to reveal the pattern of wood fonnation in plantation-grown teak at three different localities in India. Rainfall and age were the two important factors that influenced cambial activity. Cambial reactivation occurred during March-April in both years. The pre-monsoon showers broke the cambial donnancy at all three localities. Almost a month's interval was observed between bud break and initiation of radial growth . Irrespective of age and locality, a peak period of cambial activity occurred during June-July. Dormancy began during October-December, depending on the age of the trees and locality. Juvenile trees and those grown in relatively high rainfall areas had a prolonged cambial activity and retained foliage throughout the year. They produced wider rings with higher proportions of latewood. Irrigation of 5-year-old trees led to the loss of typical ring porosity of teak wood; their first three growth rings were more or less diffuse-porous. This is attributed to uninterrupted cambial activity resulting in production of rather uniform-sized vessels.

No abstract

The three major teak provenances of the Western Ghats in India were characterised in terms of mechanical and anatomical wood properties. Within the same age of 21-year-old plantations, teak from the North Kanara provenance, generally known to display slow growth, had the lower values of static bending (modulus of rupture and modulus of elasticity) and longitudinal compressive stresses than the Malabar provenance (Nilambur). The weaker timber of North Kanara provenance was attributed to its relatively high percentage of parenchyma and low percentage of fibres in the narrower rings, probably as an adaptation to nutrient-rich soil condition. Observations of 65-year-old plantations reveal that there was a trend for bending stiffness (modulus of elasticity) and maximum stress (modulus of rupture) of the timber to be highest towards the southernmost geographic location (Konni) within the latitudinal range of 9° to15° S with a greater percentage of cell wall (with higher lignification) despite the slower growth rate and well defined ring-porosity with wider bands of earlywood parenchyma tissue. The study thus underlines the need to recognise the provenance source of variation to explain the varied growth-structure-property relationships of teak and to utilise the Indian genetic resources to the optimum in future teak improvement programmes.

Natural decay resistance of teak wood grown in home-garden forestry and the factors influencing decay resistance were determined in comparison with that of a typical forest plantation. Accelerated laboratory tests were conducted on 1800 wood samples drawn from 15 trees of three planted sites. Analysis of variance based on a univariate mixed model showed that planted site, fungal species, and their interaction terms were important sources of variation in decay resistance. With increasing decay resistance from centre to periphery of the heartwood, radial position was a critical factor and the interaction effect of fungal species × radial position was significant in influencing the durability. No significant differences were found in decay resistance either between the opposite radii or due to the various possible interaction terms of radii with the site, fungal species and radial position. There were significant differences in decay resistance against brown-rot fungi between wet and dry sites of home-garden teak although differences against white-rot fungi were non-significant among the three planted sites. Polyporus palustris was the more aggressive brown-rot fungus than Gloeophyllum trabeum. The higher susceptibility of wet site home-garden teak to brown-rot decay was associated with a paler colour of the wood and lower extractive content.