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Sundarbans forest regeneration Natural regeneration refers to renewal of a tree crop by natural means, as opposed to artificial regeneration by means of planting or sowing as done in mangrove plantation. The mangrove of the Sundarbans is dependent on natural regeneration for its existence. Over the greater part of the forest, seedling recruitment was sufficient for replacement of the harvested trees. The average number of seedlings appearing per year was about 27,750/ha although recruitment densities varied considerably among different parts of the forests. Heritiera fomes, Excoecaria agallocha and other species together constituted about 24, 54 and 22 percent of the recruits (three months old seedlings), respectively.

Salinity of the area apparently influences the regeneration density which decreases with increasing level of salinity. There is year to year variation in recruitment. However, salinity appears to have little influence on these variations. Variation in seedling recruitment among the three salinity zones seems to be significant. Seedling recruitment for H. fomes, E. agallocha, and other species shows highly fluctuating values over the years. Such fluctuation might be due to the existence of periodicity in the seed production of some species.

Nipa Palm locally known as golpata, Nypa fruticans, is a member of the family Arecaceae (= Palmae). It is a mangrove species, distributed throughout the mangroves of Asia, Oceania and east coast of Africa. It is a trunkless palm with tall erect leaves (3-9m long). The underground stem is a short horizontal rhizome with massive dense root system. Nipa generally occurs in the mangroves along the banks of the rivers and streams, and needs regular inundation. In the Sundarbans it grows in slightly and moderately saline zones. People in south-western parts of Bangladesh grow nipa in the agricultural fields to a limited extent for domestic use. Nipa leaves are quite durable and used for thatching houses. It is an important thatching material in south-western parts of Bangladesh, particularly in the districts of Patuakhali, Bagerhat, Khulna, and Satkhira.

In many countries people make hats, baskets, umbrellas, mats etc from nipa leaves. Tapping of growing inflorescence exudes sap that produces vinegar and alcohol. Sap on boiling produces brown sugar. Endosperms of young seeds are edible. Forestry Master Plan of Bangladesh published in 1992 estimates that about 2,100 metric tonnes of nipa leaves are harvested annually from the Sundarbans. Nipa leaf collection provides employment of about 19,000 people.

Nipa regenerates naturally in the mangrove. It can also be propagated artificially by planting seedlings along the muddy banks of mangrove forests and also in exposed shorelines. Generally seedlings are raised on nursery beds regularly inundated by tidal water. Usually two months old seedlings attaining height of about 25cm are suitable for planting. Generally leaves are harvested at the age of five and done annually. Harvesting is done once in a year, usually during dry months (October-February). All leaves are harvested except the unopened leaf and the leaf next to it.

Tidal Forest forest subject to tidal action. In Bangladesh the Sundarbans represents the tidal forest and constitutes the largest continuous mangrove forest in the world. The forest is located at the southern extremity of the Ganges river delta ie the plain bordering the Bay of Bengal to the south. This is a reserve forest and has been divided into four administrative ranges and 55 compartments. The forest is enriched with about 70 tree species, many of which are commercially important. The Sundarbans is a deltaic swamp. The land surface is flat and the elevation is hardly 3 m above mean sea level. The entire area is intersected by a complex network of streams and rivers varying considerably in width and depth. Sundri (Heritiera fomes) and Gewa (Ecoecara agallocha) are the dominant tree species. The height of the forest varies from 5 m to 20 m. As regards density, about 50% of the area have more then 70% canopy closure.

A number of rivers namely Passur, Sipash, Arpangasia, Malaencha, and to a slight extent Jumuna and Raimangal have indirect connection, and they receive the overflow of the Ganges during rains. They also receive a considerable amount of local drainage throughout their long and meandering courses during the monsoon. Now, only the Baleswar has direct connection and is responsible for fresh water supply to the eastern part of the forest. The soil is finely textured and the sub-soil is stratified, which at greater depth is compact. Tides in the Sundarbans are semi-diurnal with a small diurnal irregularity. Annual rainfall is in the range of 1640-2000 mm. On an average, 80% of the total annual rain is received from June to October.

Bengal Tiger (bagh) one of the largest living cats on earth, belongs to family Felidae, order Carnivora. The Bengal Tiger (Panthera tigris tigris) is recognised as the national animal of Bangladesh and is renowned as the Royal Bengal Tiger. Its body is rich yellow to reddish ochre in colour with vertically arranged black stripes, more pronounced towards the rump and thighs; its underparts are whitish. Its cubs are born with stripes. The yellow tail has a series of black rings and ends up with a black tip. The backside of the ears is black and has a clearly visible white spot. The animal has round pupils, retractile claws, head-body length 140-280 cm, and a tail measuring 60-110 cm. Its height at its shoulder is 95-110 cm; males weigh 180-280 kg and females 115-185 kg; the female is smaller. The heaviest tiger that has been recorded in the Guinness Book of Records at 465 kg is the Amur (Siberian) Tiger (Panthera tigris attaica). Siberian tigers are also generally the heaviest, with adult males often weighing over 272 kg and male Sumatran tigers (P. t. sumatrae) weigh only about 113 kg. Tigers are mainly nocturnal, and normally solitary except when breeding. They prey on medium to large mammals such as deer, wild pigs and porcupines. They can bring down animals twice their size. Prey species determine how many tigers can survive in a given area. An agile animal, it swims well, and patrols its territory by marking it with droppings and other signs. Tigers are monogamous and usually give birth to 2-5 cubs after a gestation period of about 14-15 weeks; the majority of the cubs are born between February and May and nursed by their mothers for 5-6 months. The young cubs stay with their mother for a year or more. A female becomes sexually mature in 3 years and a male in 4 years. An extremely adaptable animal, P. tigris lives in a variety of habitats, from tropical forests to mangrove swamps to deciduous woodlands. Tigers can also be found in a wide range of climates and range from the jungles of the subcontinent to the snows of the Russian Far East. In Bangladesh tigers were once found in every forest, but are now confined to the mangrove forests of the Sundarbans, and are treated as a critically endangered species. Of the eight subspecies of tigers five still survive: the Bengal Tiger (Panthera tigris tigris) lives in Bangladesh, Bhutan, China, India, Western Myanmar and Nepal; the Amur (Siberian) Tiger (P. t. attaica) in Siberia, Manchuria and Northeast China; the south China (Amoy) Tiger (P. t. ameyensis) in China; the Sumatran Tiger (P. t. sumatrae) in Sumatra; and the Indo-Chinese Tiger (P. t. corbetti) in Cambodia, China, Laos, Malaysia, Eastern Myanmar, Thailand and Vietnam. Three subspecies of tigers the Javan Tiger (P. t. sondaica), the Bali Tiger (P. t. balica), and the Caspian (Turan/Hyrcanian) Tiger (P. t. virgata) have become extinct in the last 50 years. Today it is estimated that fewer than 7,000 tigers survive in the wild in the following countries: Bangladesh (300-362), Bhutan (67-81), China (110-140), India (2,500-3,750), Myanmar (230-465), Nepal (93-97), Russia (330-337), Vietnam (200), Cambodia (150-300), Laos (?), North Korea (c 10), Thailand (250-501), Malaysia (491-510), and Indonesia (400-500).

In Bangladesh habitat loss, loss of prey, poaching for skin and other body parts, and killing by man are the major threats to tigers, so day by dayt Tiger has been deceasing in The Royal Bengal Tiger has been included in the Convention on International Trade in Endangered Species (CITES) Appendix 1, and in the 3rd Schedule of the Bangladesh (Wildlife) (Preservation) (Amendment) Act, 1974.
 

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