Comparative decay resistance of plantation-grown and naturally-grown teak wood (Tectona grandis L.f.)

Abstract

Teak (Tectona grandis L.f.) is one of the most popular tropical timber species for its natural durability. The sapwood, the outer, middle, and inner heartwood, and the pith of plantation-grown teak in Indonesia and naturally grown teak in Myanmar were tested for decay resistance (a major component of natural durability), applying an accelerated decay test according to JIS Z 2101 (1994), and using a white rot fungus (Trametes versicolor) and a brown rot fungus (Fomitopsis palustris). Wood blocks 20 × 20 × 10 mm in size were cut from discs across the radius of the stem. The percentage mass loss in each block caused by decay was obtained after 12 weeks of incubation with these fungi. Mean mass losses due to T. versicolor were respectively as follows for plantation-grown, naturally-grown (No. 1), and naturally-grown (No. 2) teak: sapwood 21.4%, 7.1%, “no data”; outer heartwood 0.6%, 3.6%, 6.6%; middle heartwood 2.3%, 6.5%, 5.7%; inner heartwood 10.3%, 9.6%, 6.0%; pith 13.0%, 15.3%, 8.2%. Losses due to F. palustris were, respectively: sapwood 7.5%, 3.0%, 7.5%; outer heartwood 0.0%, 2.5%, 2.7%; middle heartwood 0.0%, 2.2%, 2.3%; inner heartwood 4.9%, 2.0%, 3.4%; pith 13.6%, 8.4%, 8.0%. Durability was classified with reference to Osborne (1970), based on the mean percentage weight loss of heartwood caused by fungal decay. Only the outer and middle heartwood were generally durable in both plantation-grown and naturally grown teak specimens. The inner heartwood was moderately durable, but pith durability was low. No clear differences in decay resistance were found between plantation-grown and naturally-grown teak.