Country reports

Bamboo resources, management and utilization in Bangladesh - Ratan Lal Banik

Bamboo resources, management and utilization in Bangladesh - Ratan Lal Banik

Chief Research Officer, Bangladesh Forest Research Institute, Chittagong.

Introduction

Area and habitats: Bangladesh is located between 20°34' and 26°39' North latitude and between 88°01' and 92°41' East longitude. The country is bounded by India on the West and North, India and Burma on the East and Bay of Bengal on the South. The major forest areas are located in the eastern and southwestern parts of the country. The country has a total land area of 14.4 million ha of which 0.93 million ha are waterways, 8.5 million ha - net cropped area, 2.67 million ha - uncultivable land and 2.2 million ha - state forests. Most of the land that is flat with rich alluvial soil lies in the active delta of three of the world's major rivers - the Ganga, the Bramaputra and the Megna. In the border areas of the east and southeast, there are hills rising over 1000 m with steep difficult terrain. The total population is about 108 million with a density of 750 per km² which is one of the most highest in the world. The present growth rate is 2.18%. The per capita income is US$ 160 (World Bank Report)¹. Forestry sector accounts for only 4.14% of the nation's total GDP at current price.

¹ 1US$ = Taka 50.60

Table 1. Classification of Bangladesh forests

Type	Area (Million ha)
Mangrove forest	0.67
Hill Forest	0.67
Plain land forest	0.12
Unclassed state forest	0.73
Village groves	0.27
Total:	2.46

Bangladesh has a subtropical monsoon climate. While there are six seasons in a year, winter, summer and monsoon are prominent. Winter, which is quite pleasant, dry, begins in November and ends in February, with temperature variation of 7.2°C to 12.8°C minimum to 23.9°C to 29.4°C maximum. Monsoon starts in June and continues up to October. This period accounts for 80% of the total rainfall. The average rainfall varies from 1270 mm to 5080 mm. The mean relative humidity varies from 73% to 82%.

Bamboos in different habitats: There are usually, but by no means always, scattered trees typical of the semi-evergreen to semi-deciduous climax standing singly or in groups over the bamboo especially in low-lying areas. Bamboos generally invade abandoned fields after slash and burn agriculture (Jhuming). The bamboo rhizomes in a natural forest are left after jhuming which rapidly regenerate into pure bamboo forests covering wide areas as a fire climax. Healthy bamboo clumps are found in well-drained, sandy loam to clay loam soil with good amount of organic matter on flat or gentle slopes of the hills. The common soil colours are yellow, brownish yellow or light reddish yellow. A wide range of textural variation and soil depth, however, do not affect normal bamboo growth provided the drainage, rainfall and temperature conditions are favourable.

Seven species of bamboos grow naturally in the forests of Bangladesh. Among them muli bans (Melocanna baccifera) is most common. Other species - mitinga (Bambusa tulda), orah (Dendrocalamus longispathus), dalu (Neohouzeaua dullooa Syn. Schizostachyum dullooa) and kali (Oxytenanthera nigrociliata) occur sporadically either in association with muli or in isolation forming small patches of pure stands. The other two species lata (Melocalamus compactiflorus) and pecha (Dendrocalamus hamiltonii) are localized only in limited areas of Cox's Bazaar and Sylhet forests respectively. The long rhizome necks of Melocanna clumps have the habit of spreading and quickly cover the vacant space of the hills by producing culms within a short time provided the plant is not disturbed. The plants thrive well on moist sandy clay loam alluvial soils and on the well-drained residual soils consisting of almost pure stands, even to the summits of low sand hills. Bambusa tulda is another comon bamboo generally found to grow as undergrowth sporadically or in patches on the flat alluvial deposits along streams in the mixed deciduous forest and also along the banks of the dry water courses. The species is also being cultivated in the homesteads of Bangladesh. Dendrocalamus longispathus has been naturally distributed chiefly along the streams and in the moist parts of the upper mixed forests, on fertile loam. The species is rarely seen on the hill tops or drier slopes.

Village Bamboos: Among the bamboo species cultivated in different parts of Bangladesh barua, balkua bans (Bambusa balcooa), baizzya, jai, bariala (B. vulgaris), mal, makhal (B. nutans), mita (B. tulda) and talla, makhla (B. longispiculata) are most common. In ranking village grown species B. balcooa and B. vulgaris are at the top of the list. The former is more common in the northern and western districts whereas the latter is frequently cultivated in the south and eastern part. Other cultivated species in the plains of Bangladesh are - bish kanta (B. bamboo var. spinosa), pharua (B. polymorpha), sharna bans (B. vulgaris var. striata), burma bans (D. membranaceus), lathi (Dendrocalamus strictus), bhudum (D. giganteus), rupai (Thyrsostachys oliveri), and thai bans (T. siamensis). B. nutans and B. vulgaris are also cultivated on a small scale on the hills. It appears that these species can be cultivated on the plain land having pH 6-8, and on the hill soils of pH 4.5-5.5.

All the natural and cultivated bamboo species of the country are clump forming types. The forest bamboo species are thin-walled and not so tall like village grown species. Melocanna baccifera, a major forest bamboo, is somewhat different under natural conditions and the boundary of an adult clump cannot be distinguished, and isolated culms emerge at long distance (1-1.5 m) from each other from the spreading rhizome system.

Impact of extraction: Gradual conversion of bamboo forests into plantations through clear felling, burning and encroachment of land have created adverse impact on the areas of bamboo vegetation. It is estimated that the annual loss of bamboo area is about 2.3 percent (Banik 1993a). Previously, the shifting cultivation cycle was approximately 30 years. Presently, the cycle has been shortened to 4-5 years due to population pressure and scarcity of land. Moreover, overexploitation, illicit felling and inadequate supervision have gradually decreased the density, degenerating the culm size in the forest. As a result the forest bamboo resources are depleted. In heavily burnt and grazed areas a special type of small sized clumps of M. baccifera, locally known as tengra muli or nali bans, regenerates successfully. The clumps are usually 5-8 m tall with many small diameter (1-3 cm at mid culm) thick-walled culms. This bioform might have evolved to adjust and survive in adverse habitats.

Genera and species: There are about 9 genera and 33 species of bamboos growing throughout the country. The genera are- Bambusa, Dendrocalamus, Dinochloa, Gigantochloa, Melocalamus, Melocanna, Oxytenanthera, Schizostachyum (Neohouzeaua), and Thyrsostachys. Most of the species belong to the genera Bambusa and Dendrocalamus while the remaining genera have only 1-2 species each.

Patterns of distribution: Semi-evergreen and semi-deciduous forests in the hills of Chittagong Hill Tracts, Cox's Bazaar, Sylhet and Northern Mymensingh of Bangladesh have seven naturally grown bamboo species either as understorey or pure stands (Fig. 1). No natural distribution of any bamboo species can be seen in the sal (Shorea robusta) forests. Bamboos also do not grow in the mangrove forests of Sundarbans. In the villages bamboos grown in the flood plains can tolerate short seasonal floods. Flooding for a longer period is unfavourable for growth of bamboo species.

Fig. 1. Distribution of both natural and cultivated bamboos in different forest types, rainfall and temperature zones of Bangladesh.

Distribution of cultivated bamboo species in the plain districts seems to be related to the choice and liking of planters, utility values of the species and availability of planting materials.

Important commercial species: On the basis of socioeconomic and environmental importance the following 10 species are the priority bamboos of Bangladesh.

Scientific name	Local name
Melocanna baccifera (Roxb.) Kurz	Muli, Nali bans
Bambusa vulgaris Schrad.	Bariala, Barak, Baizzya bans
B. balcooa Roxb.	Barua, Bhaluka
B. tulda Roxb	Mitinga, Mita, Nitai bans
B. longispiculata Gamble ex Brandis	Ora, Khag bans
B. polymorpha Munro	Pharua, Bethua bans
Schizostachyum dullooa Majumdar (Syn. Neohouzeaua dullooa A. Camus)	Dalu, Chunga bans
Thyrsostachys oliveri Gamble	Rupai, Rangoon bans
Dendrocalamus hamiltonii Nees and Arn.	Pecha

Dendrocalamus hamiltonii, Melocalamus compactiflorus and Schizostachyum dullooa are the threatened species in Bangladesh. Two forest inventories, in 1961-63 and 1984 were conducted with foreign assistance to survey the bamboo resources in Chittagong, Chittagong Hill Tracts and Cox's Bazaar forests. The inventory of bamboo resources in these areas is not yet complete due to large scale death of the major forest bamboo species, Melocanna baccifera, which flowered gregariously during 1961-63. In 1984, the areas were not safe to survey due to tribal insurgency. During 1985, an inventory was done in Sylhet forest. The village forest resources survey was done in 1980 and also in 1990. However, from the sample survey and bamboo harvesting records of the Forest Department and the village forest inventory reports, an assessment of annual bamboo supply and demand of the country were made and projected for future use (Table 2).

Table 2. Estimate of bamboo supply and demand (million culms)

Source: Banik 1993a

Stem	Years
	1998	1999	2003	2008	2013
Natural forest supply
- Potential supply	193.7	222.1	293.6	138.8	65.7
- Available supply	128.7	152.3	228.3	110.3	49.4
Village supply	527.5	527.5	527.5	527.5	527.5
Total supply	656.2	679.8	755.8	637.8	576.9
Demand
- Domestic	576.1	621.7	666.6	712.3	730.1
- Urban housing	30.1	34.3	38.5	42.7	47.0
- Industrial	100.1	105.1	110.4	113.1	124.4
Total	706.3	761.1	815.5	868.1	901.5
Surplus/(Deficit)	-50.1	-81.3	-59.7	-230.3	-324.6

NB: Potential supply: The amount present in the forest. Available supply: Harvested amount from Forest Deptt. and Tea Gardens. Domestic demand: Rural house construction, agricultural implements, community building, etc. Industrial demand: Pulp and paper, cottage, transport (boats, rickshaw hood and bullock cart etc.).

Conservation: The current accelerated rate of deforestation alarmingly erodes the genetic resources of trees and bamboos. Therefore, there is an urgent need to conserve genetic resources of bamboos both in their natural habitat (in situ) and in ex situ conservation plots. During 1993, the Forestry Master Plan (FMP) of Bangladesh emphazied the in situ conservation of bamboo stands in the natural ecosystem. Rich natural forest reserve areas with bamboos were divided into two zones- “buffer zones” and “core areas”. The people of the adjacent village managed and used the buffer zone for their own needs. The permanent linear sample plots (PSP) not less than 50 x 200 m were established inside the “core areas” of different forests in such a way that the maximum number of species and topographic variations were included.

Community-based conservation: The tribal people settled in different forests use bamboos for house construction, agricultural implements and for edible shoots. Some of the individual farmers of the community have been cultivating and maintaining a number of clumps in the nearby natural habitat to meet their demands. Such community-based conservation of S. dullooa, D. longispathus and M. baccifera can be seen in many areas of Chittagong Hill Tracts, Sylhet and northern part Mymensingh forest. The tea garden labourers and local Khasia tribes also maintain some natural patches of Dendrocalamus hamiltonii on sustainable basis and use them for various purposes.

Temple-based conservation: Most of the hill tribal people are buddhists such as Chakma, Mog and Barua residing in Chittagong, Chittagong Hill Tracts and Cox's Bazaar and have established a number of temples. Majority of the temples cultivate Dendrocalamus giganteus and Bambusa polymorpha.

The in situ bamboo vegetation is often threatened due to uncontrolled biotic interference and therefore, it was necessary to centralize and conserve the different bamboo species in protected areas. The efforts to collect and centralize of the species and their variants were started since 1972-73 inside the campus of Bangladesh Forest Research Institute (BFRI), Chittagong. The total land of the bambusetum is approximately 1.0 ha under the influence of tropical monsoon climate having a range of annual air temperature 10-35°C, soil temperature 22-29°C at 50-200 cm depth, and total annual rainfall 2500 mm-3000 mm. Rainfall is high during the last part of May to August and dry months are mostly from November to March. So far 36 species of bamboos have been collected from different parts of the country and two from Thailand. Bambusa bambos was collected from different parts of Bangladesh and one seed source from Kanchanburi, Thailand. The monopodial species Phyllostachys pubescens was collected from Zhejiang Province of People's Republic of China. Seeds were obtained in 1994 and seedlings were raised immediately and then centralized in the bambusetum. All the species have been planted serially in lines. In two cases (Bambusa bambos and Dendrocalamus brandisii) tissue culture plantlets were raised locally. The planted propagules of various species include offsets, part-clump, branch cutting, seed and seedling. Each species been planted in one or more lines collected from different sources.

The National Botanical Garden of about 85 ha was established in 1962 at Mirpur area about 30 km north of Dhaka city, the capital of Bangladesh. The ground is more or less flat with slight reddish brown to ash colour soil. The centralization of bamboo species was started in 1974. Till 1998, 20 species of eight genera were cultivated in the garden, occupying about 0.4 ha land.

The Balda Garden, Dhaka was established in 1920 inside the central city area of Dhaka. One clump of yellow bamboo (Bambusa vulgaris var. striata) collected from Philippines in 1976, two clumps of D. giganteus and one clump of black bamboo (Gigantochloa sp.) collected during 1920 from unknown source are growing in the garden.

Plantation development: A systematic investigation on the variability of growth and performance of different provenances of five major bamboo species (B. balcooa, B. vulgaris, B. longispiculata, B. tulda and M. baccifera) of Bangladesh was initiated at BFRI. The country was divided into three parts - north, central and south. In each of these parts 5 major bamboo growing districts were taken as representative and from there 20-25 villages were treated as one unit of collection for each species. From the selected clump of a bamboo species a number of offsets were collected as planting stock for the multilocation trials. In some areas farmers or members of local community have conserved specific bamboo species and of different germplasm unrecorded in the past. In some areas exotic species are included. The plants are well conserved and maintained. Majority of the farmers in the areas of Sylhet-Comilla, bordering Indian State of Tripura, have cultivated and conserved Thyrsostachys oliveri in their homesteads. No seed bank of bamboo species is available in the country. However, seeds of some flowering plants are preserved at BFRI.

Genetic Resources

Details of population structure and genetic resources of different bamboo species of the country have not yet been studied. However, it is said that most of the naturally grown forest bamboo species have more than one population in the country. The flowering and growth behaviour of M. baccifera includes at least three populations in different parts of the forest. A distinct biotype of Bambusa vulgaris has been cultivated at the Cox's Bazaar and southern part of Chittagong. This biotype is short and bushy in comparison to that of common tall biotype of the species. Culms are rarely infected with blight disease. Locally the bamboo is known as “Kanta Bizzya Bans”. The southern part of Chittagong and Cox's Bazaar areas frequently experience cyclone and tidal hazards. For this reason people of these localities have been cultivating and maintaining the short bushy type of B. vulgaris. Many species like B. tulda, B. polymorpha, B. vulgaris and D. longispathus, O. nigrociliata show phenotypic variations in culm colour, length of the culm sheath, branching pattern, and clump nature (congested/open), etc. Differences in flowering duration among the clumps of D. longispathus were recorded. D. longispathus clumps grown from seedlings collected from the forests show different variations. Two such variants are growing in the arboretum named D. longispathus var. dholai and D. longispathus var. koila. They represent less than 0.2% of the entire population (Hasan 1979).

Selection, breeding, diversity identification and centralization of the germplasm are the main methods adopted for genetic improvement of bamboos in Bangladesh. The Silviculture Genetic Division of BFRI are working on this aspect.

Phenology: The bamboo clumps produce culms generally from the month of May or June and continue for 6 to 7 months ending in October or November (Banik 1993b). The species exhibited different durations of shoot emergence periods varying from 4 to 8 months. The total culm elongation periods of B. balcooa and B. vulgaris was 75-85 days, and 55-60 days for M. baccifera. The rate of daily culm elongation varied from 40-70 cm depending on the species. The natural mortality of emerging culm was 28-69 percent in thick-walled, tall species, compared to lower rates (9-37%) in thin-walled and small size bamboo species.

The life of culms in the clumps was long (10-13 years) in B. balcooa and D. giganteus, while it was short (5-10 years) in most of the thin-walled bamboo species. In the culms of B. balcooa, B. longispiculata, B. tulda and B. vulgaris, production and growth (height and diameter) of full grown culms gradually increased up to fifth year of planting then stabilized and gradually declined. In most of the species clump expansion took place up to 8-10 years whereas in M. baccifera clump continued to expand even after the age of 15 years.

Hybridization: Natural hybridization may take place between different species of bamboo when flowering occurs at the same time and in the same region. A number of clumps were raised from seeds of Dendrocalamus longispathus and 17 of them planted at the BFRI bambusetum. A few clumps showed culm sheath form of Oxytenanthera nigrociliata and bud characters of D. longispathus. One clump showed branching and long internodal characters of S. dullooa with the bud characters of D. longispathus. Thus it seems natural hybridization of D. longispathus X S. dullooa and D. longispathus X O. nigrociliata occured in the past (Hasan 1979)

During 1984-85, both Bambusa bambos and B. tulda flowered together in the bambusetum. A trial was made to cross the two species. A number of hybrid seeds were obtained from the cross. Seedlings were raised and planted in the field station. Some hybrid seedlings showed mixed characters of both species. The same individual developed thorns, a character of B. bambos, and also the big-sized leaves and culm-colour of B. tulda. Further evaluation and studies are underway.

Mutation breeding: Recently in BFRI seeds of B. bambos were irradiated with gamma rays, with doses of 10, 20 and 30 krads. Seeds treated with 10 krads germinated well and few of those with 20 krads. Presently the plants are 3 years old and have developed clumps. Some of the clumps showed bushy and dwarf growth forms, some did not develop any thorns on the branches unlike the normal plants of the species, and a clump had very small-sized leaves with slight wavy margin.

Propagation methods

Offset methods: Bamboos are conventionally propagated by offsets. Offsets are normally obtained and transplanted just before the rainy season or after a pre-monsoon shower, i.e. from mid March to April. If collected later, when culms are emerging, the buds on the rhizome will be elongated and liable to damage and as a result the offset will fail to survive in the field. Success of offset planting in thin-walled bamboo species is relatively poor and varies greatly from species to species. The offsets are bulky and heavy (4-30 kg per propagule) and therefore, difficult to handle and transport. Availability of propagules per clump is also limited and costly. Therefore, this method has limitation for large-scale bamboo plantations (Banik 1987b, 1995a). Besides the offset method, other techniques of vegetative propagation for bamboos have been described (Banik 1995a). These are pre-rooted branch cuttings, culm cuttings, layering, macroproliferation of seedlings, etc. Among them branch cutting and culm cutting techniques are easy and can be used every year.

Prerooted and prerhizomed branch cutting: Most of the thick-walled cultivated bamboo species in Bangladesh have stout branches having spontaneous in situ rooting and rhizome at the swollen base (Banik 1980, 1987b). Aerial roots and rhizomes of such cuttings are not always active. Therefore, these cuttings have to be collected from the nodes of the standing culms during April to June and be placed in the sand media of propagation beds. A propagation bed is a 3-layered sand bed, each of the layer 7-10 cm deep. The bed remains well drained. A propagation bed is 1.2 m wide and 12 m long in size, situated on level ground in the nursery. The collected branch cuttings from the culms are placed on the sand media under mist for one month. Within 30 days, the branch cuttings produce profuse active roots.

Culm cutting: These are culm segments with 1-3 nodes with buds or branches. The culms selected for the cuttings should not be more than 2 years old and buds should be healthy. The cuttings are placed in the sand bed for rooting. About 30-70% success can be obtained depending on the species. In some species like Dendrocalamus longispathus success can be enhanced in both branch cuttings and culm cutting treatment by treating them with IBA or NAA (100-150 ppm). Once rooted, the cuttings are transferred to polythene bags and kept in the nursery, with regular weeding and watering. Like seedlings, cuttings are kept in the nursery at least up to the next monsoon. Survival of these types of cuttings in the field is high, almost 85-90%. The culms can be harvested after 3-5 years in plantation.

Macroproliferation of seedlings: The seedlings raised can be multiplied by rhizome separation. This method is known as macroproliferation (Banik 1987b). One five-month old B. tulda or D. longispathus seedling may yield three to five multiple seedlings. However, Melocanna seedlings cannot be multiplied because the species usually produces one stem up to nine months. For better survival (about 80-90%) in the field, less than one-year old seedlings should not be transplanted. The seedlings are to be planted out during the rainy season.

Tissue culture: Tissue culture research on bamboo was started with the support of IDRC at BFRI, Chittagong. Studies were made on Bambusa bambos, B. glaucescens, B. nutans, Dendrocalamus brandisii, Melocanna baccifera, and Thyrsostachys siamensis. MS and B5 media were suitable. Both solid and liquid media were used supplemented with BAP, Kn, 2ip as cytokinins and IBA, NAA as auxins. Direct proliferation as well as callus formation resulted. Better success was obtained with the juvenile (seedling) materials. The application of micro-propagation is, still limited since the proliferation and rooting of vegetative explants (mostly buds) are relatively poor. Further research is in progress (Banik 1995b).

Using seeds: Bamboo species exhibit exceptional flowering behaviour (Table 3). The possible next flowering year of the major bamboo species of the country is forecasted on the basis of their estimated interseeding (flowering cycle) period. Both barua (B. balcooa) and bariala (B. vulgaris), the most common bamboo species cultivated in the villages, usually flower very sporadically or in isolated clumps after many years. But they do not produce any seeds. Estimates were made on analyzing the past flowering records of each of the major bamboo species in the country. Estimated ranges of flowering cycles of different bamboo species were found to be within 20-80 years but majority within 30-50 year cycles (Banik 1980; Hasan 1973).

Table 3. Bamboo flowering cycle

Species name	Flowering nature	Last gregarious flowering year (location)	Estimated cycle (years)	Forecasted Flowering year
Melocanna baccifera	Many gregarious rarely sporadic	1957-61 all hill forests	30 ± 5 45 ± 5	1987-1991 ± 5, 2006 ± 5, initially sporadic then gregarious and finally sporadic, 10-15 year flowering wave.
Bambusa tulda	Frequently sporadic and irregular, occasionally gregarious	1977-79 Shishak 1978-80 Adampur Lawachara	20 ± 5	1997 ± 5, 1999 ± 5, 1998 ±5, 2000 ± 5 (frequently sporadic throughout the forest)
Dendrocalamus longispathus	Often sporadically, occasionally gregarious	1967-72 Shishak 1974 Rankhiang 1972 Rangarh	30 ± 2	1997 ±2, 2004 ± 2, 2002 ± 2
Oxytenanthera nigrociliata	Sporadic and, occasionally gregarious	1978 Pablakhali	47 ± 3	2025 ± 3
Neohouzeana dullooa	Sporadic and occasionally gregarious	1974 Kassalong	45 ± 2	2020 ± 2
Dendrocalamus strictus	Gregarious, rarely sporadic	1975 Cox's Bazar	50 ± 3	2025 ± 3
Dendrocalamus hamiltonii	-do-	1996-98 BFRI, Sylhet Forest	40 ± 5 90 ± 5	2036 ± 5 2086 ± 5
Bambusa vulgaris	Rarely in flowering state, no seed production	1979 (a few clums in Chittagong)	80 ± 8	Any time any where, but likely to confine in a very few clumps
Bambusa balcooa	Rarely in flowering state, no seed production	1983-85 Isolated clump in Mymensingh and Rangpur	40 ± 5	Any time any where but likely to confine in isolated clump
Bambusa longispiculata	Sporadic, rarely gregarious	1985-88 (Dinajpur)	20 ± 5	2005 ± 5 2008 ± 5
Bambusa polymorpha	Gregarious, sporadic	1982-83 Sporadically in Sylhet	50 ± 5	2032 ± 5 2033 ± 5
Dendrocalamus strictus	Gregarious and sporadic	1984-86 (Gregarious in Chittagong, Sylhet)	45 ± 5	2029 ± 5 2031 ± 5

Bamboo seeds both in size and weight show variations (Table 4). Most of the seeds are small, grain like, wheat coloured and covered with glumes. Seed production per clump varies from 15-90 gm. One full-grown clump of Melocanna baccifera produced 25-40 kg seeds during flowering period before dying (Banik 1989). Fruits of M. baccifera are edible with thick, fleshy pericarp and a curved beak (Fig. 2)

Fig. 2. Fruit of M. baccifera enlarged

Seed collection is a vital component since bamboo flowers irregularly. Generally, seeds produced in the early part (mid February-May) of the season are healthy and more viable. Bamboo seeds germinate well under shade than in sunlight. Seeds should be sown in the polythene bags just after collection. The germination medium (soil and cowdung 3:1) should be wet but not waterlogged. Seeds start germinating within 3-7 days of sowing and continue up to 15-25 days.

Bamboo seeds are short lived, losing their viability within one to two months (Banik 1987a). Seeds of Bambusa tulda can be stored upto 18 months by storing over silica gel in a desiccator. At normal room condition the life span of Melocanna baccifera seed is about 35 days, which can be increased up to 45 days when stored in an air conditioned room, and can further be prolonged to 60 days when stored with dry sand in jute bags.

The seed weight had a significant effect on the survival of seedling. M. baccifera seeds can be graded into three groups on the basis of weight. The light weight seeds were not desirable for nursery stocks. Seedlings survived up to 70-75 % when raised from the seeds heavier than 50 g, and survival was 56 % when raised from light weight seeds (7-16 g).

Table 4: Seed characters of some bamboo species in Bangladesh

Name of the species	Seed shape and weight
Forest species
Melocanna baccifera	Large and obliquely ovoid, thick fleshy onion-shaped and the apex terminating in a curved beak, green with smooth surface. The weight of a seed varies from 7.0 to 110 g and diameter from 22 to 60 mm, 45 to 70 seeds (average) per kg.
Dendrocalamus longispathus	Small like coriander seed, 1350 seeds (average) per 10g.
D. hamiltonii	Boadly ovoid, rounded at the base, seeds (average) 265-270 per 10 g.
Bambusa tulda	Small like wheat grain, 150 seeds (average) per 10 g.
Oxytenanthera nigrociliata	Small like wheat grain, 265 seeds (average) per 10 g.
Melocalamus compactiflorus	Like chest nut or betel nut. The weight of a seed varies from 2 to 20 g.
Village species
Bambusa vulgaris	Do not produce seed.
B. balcooa	Do not produce seed.
B. longispiculata	Small like wheat grain, 145 seeds (average) per 10 g.
B. polymorpha	Small like wheat grain, 1250 seeds (average) per 10 g.
Dendrocalamus strictus	Small like wheat grain, 515 seeds (average) per 10 g.
B. bambos var. spinosa	Small like wheat grain, 1325 seeds (average) per 10 g.
B. glaucescens	Small like wheat grain, 151 seeds (average) per 10 g.

Initially, seedlings do best in partial shade compared to direct sunlight. Complete shading over seedlings should be avoided. In the nurseries roots and rhizomes of seedlings penetrate the neighbouring polythene bags of other seedlings. This creates a mass of twisted and intermingled roots and rhizomes of seedlings. As a result, the roots and rhizomes are damaged at the time of transportation. Frequent shifting of seedlings from one bed to another helps in minimizing seedling casualities due to root rhizome intermingling at nursery stage. Seedlings need regular weeding and daily watering at nursery stage.

Fig. 3. Bamboo harvesting and transportation

Wild bamboo seedlings look like rice or wheat seedlings. They are identified on the ground below the mother clumps. These seedlings should be thinned out to minimize the competition (Banik 1988). The wild seedlings should be collected and transplanted in polythene bags containing soil mixed with cow dung. At the beginning, seedlings are to be kept under shade for three to five days for hardening, then placed under partial shade. Two to four leaved stage of wild seedlings of B. tulda and D. longispathus are the best for collection, while in M. baccifera germinating seedlings are best.

Extraction arid sustainable utilisation: The bamboo vegetation in the forests and villages, is not the same. Bamboos in the forests usually cover large tract of land from valleys, slopes and tops of the hills. In villages bamboos are cultivated in the homesteads, usually the clumps are few in number, rarely covering 1-2 ha land. Village bamboos are mostly owned by the families whereas the forest bamboos are owned and maintained by the government. Harvesting procedures in these two sectors are different.

The harvesting of forest bamboos is done on a three year rotation using selective felling. Normally, felling starts in October and lasts for about 120 days during the season. In Sylhet forest harvesting is on unit area (bamboo mahal) basis which varies from 500 to 2000 ha. So supervision of bamboo harvesting in such big area is difficult and as a result contractors most of the time ignore the cutting rules. Harvesting of bamboo crops include a series of operations as follows and as charted in Fig. 3 (Banik 1993a, b).

- The felling of exploitable bamboo stems 0.3 to 0.45 meters above the ground, their trimming and cutting into pieces for bundling then extracted by ropeway - shoulder load and haulage to river side depots.

- Transporting of bamboo includes bunching and rafting from river side depot to the yard (Banik 1994).

Labourers are always tempted to harvest bamboos from the easily accessible areas. The over cutting causes a gradual degeneration in health and size of clumps. Bamboos are seldom harvested from the steep slopes or inaccessible areas in the forest, and as a result bamboo clumps in these areas remain undercut (under exploited) and congested conditions develop.

After felling, the culms are pulled out of the clump, then limbed and trimmed for handling and cut into pieces of 1.7-3.0 m in length for road or rail transport. Generally, 5.5-6.5 m, sometimes 8 m, pieces are transported through waterways. At the beginning, small rafts of 10 000-20 000 numbers of bamboos are prepared and in the bigger streams up to the lakefront large size rafts (100 000-150 000 pieces) are made and transported. These big rafts are propelled either by a manual winch or tug boats. A contingent of 8-12 men can handle such big rafts in fair weather.

Harvesting of village bamboo: Bamboos in the village homesteads mostly occupy the backyard and the periphery of the holdings. Village species are clump-forming, usually congested in nature with large, tall, branchy culms. Moreover the mature harvestable culms (more than three years old) are in the clump centre. Therefore, harvesting is more difficult and time consuming. Due to the price hike, the rate of felling of bamboos is increasing in some villages near urban areas. Compelled by poverty and tempted by higher price, poor farmers also sell immature good looking bamboos to traders. This practice ultimately destroys the clumps by gradually decreasing the rhizome vitality. In contrast, big farmers and absentee landlords especially of northern parts of Bangladesh where bamboos are cultivated in the upland as patches on small farms, do not usually fully sell or harvest their bamboos. As a result, in this part of the country the clumps are in a congested condition and the yield will be gradually decreased.

Rehabilitation of degraded areas, soil conservation and water resources: Within the last decade in some degraded areas of Chittagong Hill Tracts and Sylhet nearly about thousand hectares of bamboo plantations have been raised with the seedlings of M. baccifera, B. tulda and branch cuttings of B. vulgaris and B. balcooa. In the rural areas mostly on river embankment, marginal land and in homestead gardens bamboos are also being planted with seedlings and cuttings. Both farmers and NGOs are involved in this regard. As regards village bamboo plantation (mostly thick-walled species) priority lies with vacant land in homesteads. Farmers prefer planting bamboo on their own vacant homestead areas. According to them the next priority is on the canal banks, roadsides and other marginal land. The plantation programmes are well suited for local participation involving nearby villagers through community forestry activities.

Research in progress: Research on bamboo was started at BFRI in 1974. During 1980-88 IDRC supported a number of studies on taxonomy, growth and yield, provenance trials and propagation of bamboos (seed, vegetative propagation and tissue culture). Besides these, establishment of bambusetum including collecting and centralization of wild germplasm and different flowering genotypes have been progressing. Studies on reproductive biology and understanding of diversities in different bamboo species are in progress.

Species selection/introduction, provenance trials, clump selection and seedling selection studies are in progress for genetic improvement programmes.

Future research and development (R&D) activities: With the increasing demand the resource base needs more development. Strategies have been developed to improve the productivity of existing bamboo resources and raise more bamboo plantations. BFRI has developed a number of technologies which are being followed in the field by foresters, NGOs and farmers for bamboo cultivation. Besides this, audiovisual programmes explaining all the steps of propagule production, plantation raising, silvicultural activities and technique of bamboo preservation treatments would help farmers about bamboo resource management.

Utilization and economic value: The two pulp mills - Karnafuli Paper and Rayon Mills (KPM) and Sylhet Pulp and Paper Mills (SPPM) of the country have been utilizing bamboo as main raw material. The annual requirement of KPM is about 55 000 ADT or 34.4 million culms. The total quantity of bamboo utilized annually by the SPPM is around 35 000 ADT or 21.9 million culms. According to the Bangladesh Small and Cottage Industries Corporation (BSCIC) there are about 45 000 registered small scale cottage industries located throughout the country. The amount of raw material consumed by these industries is about 46 million bamboo culms. Bamboo is also extensively utilized for constructing boats, bullock carts and rickshaw hoods. For these transportation industries the total annual requirement is about 2.8 million culms.

Socioeconomically, bamboo is the most important plant for the Bangladesh people. Some 300 000 people are estimated to be employed in bamboo cutting and collecting annually from the forests. Millions of people are directly or indirectly dependent on this versatile plant in agriculture, housing, cottage industries and ritual activities. Bangladesh has about 21 ethnic groups of people mainly residing in different forest areas. Among all the forest and village grown bamboo species local people mostly utilize and prefer only four species - M. baccifera, B. tulda, D. longispathus and S. dullooa. They sometimes cultivate B. vulgaris in their homesteads for construction purpose. To the hill people, bamboo is a traditional building material. The houses are built entirely of bamboo. The floor and walls are made of bamboo splits and flattened out and then woven together. The framework of the roof is also made from bamboo. The long internodes of S. dullooa are used for carrying water in steep slopes. Bamboos are also used for many medicinal purposes. The local people identify all bamboo species using different vegetative characters. They have their own system of naming the different bamboo species and indigenous knowledge of bamboo grove management. Ethnic people usually do not harvest all the shoots as food from a clump. Harvesting is selective about 30-40% of the total number of shoots emerged in a year. Local people play an important role in conserving bamboo resources.

Research needs and constraints: The important research issues are as follows:

a) Suitable bamboo inventory methods

b) Database development for better understanding of the phenomenon of gregarious flowering.

c) Improved crop productivity.

d) Development of management systems suitable for intercropping and underplanting of bamboo for multiple land use at the initial stage of clump formation. Suitable and economical methods for harvesting bamboo, especially from inaccessible areas.

e) Inter and intraspecific genetic variability in natural bamboos and their conservation.

f) Identification of different population of each species; and

g) Development of proper method of training and extension for foresters and farmers.

References

Banik, R.L. 1980. Propagation of bamboos by clonal methods and by seeds. Pp. 139-150 in Bamboo Research in Asia. (G. Lesserd and A. Chouinard, eds.). IDRC, Ottawa, Canada.

Banik, R.L. 1987a. Seed germination of some bamboo species. Indian Forester 113(8):578-586.

Banik, R.L. 1987b. Techniques of bamboo propagation with special reference to prerooted and prerhizomed branch cuttings and tissue culture. Pp. 160-169 in Recent Research on Bamboos (A.N. Rao, G. Dhanaranjan and C.B. Sastry, eds.). CAF, Beijing and IDRC, Singapore.

Banik, R.L. 1988. Management of wild bamboo seedlings for natural regeneration and reforestation. Pp. 92-95 in Bamboo-Current Research. KFRI, Peechi, India. IDRC, Singapore.

Banik, R.L. 1989. Recent flowering of muli bamboo (Melocanna baccifera) in Bangladesh: an alarming situation for bamboo resource. Bano Biggyan Patrika 18(1&2):65-68.

Banik, R.L. 1993a. Bamboo. Forestry Master Plan of Bangladesh. Pp. 62 (8 Apendix) in Asian Dev. Bank (TA.No. 1355-BAN). UNDP/FAO BGD.

Banik, R.L. 1993b. Periodicity of culm emergence in different bamboo species of Bangladesh. Annals of Forestry 1(1):13-17

Banik, R.L. 1994. Distribution and ecological status of bamboo forests of Bangladesh. Bangladesh Jour. For. Sci. 23(2):12-19.

Banik, R.L. 1995a. A Manual for Vegetative Propagation of Bamboos. Pp. 66 in INBAR Technical Report No. 6. IDRC, Canada/FAO-FORTIP/BFRI.

Banik, R.L. 1995b. Domestication and Breeding of Bamboos. UNDP/FAO/RAS/91/004. Los Banos, Philippines.

Hasan, S.M. 1973. Seeding behaviour of Bangladesh bamboos. Bano Biggyan Patrika 5(2):21-36.

Hasan, S.M. 1979. Observation on culms and culm-sheaths of Ora bamboo raised from seeds. Bano Biggyan Patrika 8(1&2):13-26.