Cotylelobium lanceolatum

Cotylelobium lanceolatum is a large evergreen tree belonging to the Dipterocarpaceae family. In its natural habitat, the tree grows to impressive heights, developing a robust trunk with highly durable timber. Due to its physical properties, it is considered a significant resource in the regional forestry sector of Southeast Asia.

The native distribution of this species covers the tropical rainforests of Southeast Asia, including Sri Lanka. The tree thrives in environments characterized by high rainfall and humidity. Its natural range is strictly limited to tropical zones, as it requires constant warmth and moisture to sustain its physiological development throughout the year.

Botanically, the species is identified by its leathery, lanceolate leaves. It produces small, cluster-borne flowers and fruit featuring specialized wing-like structures, which facilitate wind-assisted seed dispersal. These traits allow the tree to successfully regenerate within the competitive environment of dense forest canopies.

The silviculture of Cotylelobium lanceolatum is challenging, as the species has specific ecological demands. It requires well-drained, nutrient-rich soils with a high organic matter content. The plant does not tolerate prolonged drought or extreme temperature fluctuations, making its cultivation outside of specific tropical ecosystems extremely difficult and rarely practiced in commercial plantations.

Its primary economic importance lies in its timber, marketed as "resak" wood. This lumber is prized for its high density, excellent strength, and natural resistance to decay, making it suitable for demanding applications such as boat building and heavy construction. Key threats to the tree include various xylophagous pests and fungal infections, which are common in the humid environments where this species typically grows.