Important mangrove species of the Sundarbans

Mangrove forest species ''Passur'' | Sundarbans, Bangladesh

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The floral species of Sundarbans forest are diversified and each characteristically unique. Species from Malvaceae and Euphorbiaceae family dominate Bangladesh's mangrove forest. More specifically, the flora of Sundarbans is distinguished by the abundance of sundari (Heritiera fomes), gewa (Excoecaria agallocha), goran (Ceriops decandra) and keora (Sonneratia apetala), all of which take place prominently throughout the region. While Passur (Xylocarpus mekongensis), from meliaceae family is also an important species with significant uses. 

Species Identity:
​Scientific name: Xylocarpus mekongensis
Vernacular name: Passur, Ail
Family: Meliaceae

​Distribution
The genus, Xylocarpus is represented by 5 species occurring in the mangroves of Asia, Oceania and East Africa. In Bangladesh, there are only 2 species of which Xylocarpus mekongensis is the most common in the Sundarbans and also introduced to coastal plantations on an experimental basis.

Habitat
It is found mainly in the saline areas on the northern part of the Sundarbans far from the sea in association with Amur, Keora and Baen. It grows in lowlands and swampy localities. It requires frequent tidal inundation. It can tolerate a wide range of salinity but prefers higher salinity level.

Passur tree in Sundarban

Characteristics of Passur (Xylocarpus mekongensis)

• It is a moderate size deciduous tree species attaining a height of 10 to 15 m. It has plank-like pneumatophores having stout, woody, hard, sometimes spear-shaped, conical and ridged. It does not produce aerial roots, buttress stem and coppice. In early stages it is shade tolerant but light demanding subsequently.
• It has thick bark being red to blackish colour with longitudinally fissured.
• Leaves are deep green, small, oblong, leathery, narrow and pointed at the apex. Leaf shedding occurs in winter and new leaves appeared in March-April. Annual leaf fall may be a mechanism for the removal of excess salt prior to the onset of a new growing and fruiting season.
• Flowering occurs in March-April. The flowers are small sizes and organised on an inflorescence and well perfumed.
• Fruits are round-shaped resembles to a pear having flat on top and bottom with fleshy thick coverings. The mature fruit is green externally and orange tinted within. Dropping occurs in June-July. Each fruit contains 8-10 seeds. One kg contains 75-125 seeds.
• Seeds are triangular or irregular shaped, fleshy and dark brown colour. They are buoyant and distributed to the forest floor by tidal current. Seeds are affected and damaged by the pests. It may be stored with watering for about 90 days.
• Germination is hypogeal and takes place soon after falling. It initiates within 14 days and completed by 80 days with success about 75% in nursery beds or in poly bags.
• Seedlings are raised in polybags but direct sowing in the field giving a high survival. Early development of seedling is rapid. It attaining a height of about 70-90 cm after 10 months. It is out planted in the field within fence condition and obtained a survival rate is about 90% but only 10-20% when forest floor seedlings are planted by pulling out. Seedlings are highly palatable and browsed by the deer and cattle. Annual mean height increment of the planted seedlings is about 52cm with 0.21cm diameter.
• At present, it seems to be affected by top dying in the crown areas and branches in mature treeses at moderately saline and strongly saline zones in the Sundarbans.
• Trees are harvested on a 20 years felling cycle under selection system from the Sundarbans. Its stocking declined considerably due to over-exploitation in the Sundarbans.
• Sapwood is narrow, brownish white and heartwood is deep wine-red or purplish red often with darker bands or greenish streaks. The timber is easy to saw, dull with greasy-smooth feel, without characteristic odour or taste. The wood is moderately heavy to heavy, straight or somewhat interlocked-grained, fine and even textured, highly durable, good polish and stable. Specific gravity is about 0.59 (air-dry volume) and weight is about 659.9 kg/m3. Moisture content fluctuation below 3%.

Importance and uses of Passur

• Inhabitants for wildlife and birds.
• It protects soil erosion along river and canal banks.
• Its bark is used for medicinal purposes for dysentry, diarrhoea as febrifuge.
• Leaves are good fodders for the cattle and deer.
• Flowers are the source of honey.
• It produces valuable timber used for poles and construction works.
• Wood is used for making furniture, flooring and panelling.
• Wood also used for making tool handles, cross-arms, plywood, flush doors, etc.

Passur species

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Post prepared by:
Md. Ahihul Islam, Specializations: Plantations, Forest and Climate Change
​Former official of Bangladesh Forest Research Institute.
Dated: 12 November 2019. 

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