BANGLADESH JOURNAL OF FOREST SCIENCE
A Half-yearly Peer Reviewed Journal of Bangladesh Forest Research Institute
A Half-yearly Peer Reviewed Journal of Bangladesh Forest Research Institute
Sal (Shorea robusta Gaertn. f.) is an important timber species of Dipterocarpaceae. This species has the widest distribution amongst the dipterocarps, from North-west India to Eastern India, Sikkim, Nepal and Bangladesh (Thiselton Dyer 1874, Tran Van Nao 1974, and Khan 1984). In Bangladesh it is known as sal or gazari, and occurs naturally in forests under Gazipur, Madhupur, Sherpur, Dinajpur and Comilla districts. Small patches of natural sal forest also occurs at Saltilla of Sylhet and Mainamoti of Comilla district. There are also sal plantations in Dhaka, Dinajpur and Sylhet districts (Das 1976) One timber, locally known as panniya sal, is available in the timber markets and saw mills of Dinajpur, Panchagarh and Thakurgaon districts which is usually collected excavating the river beds of those areas. This collected sal timbers remained under “pani” (water) for which it is called panniya sal.
Keora (Sonneratia apetala Buch.-Ham) is the principal species in the coastal plantations of Bangladesh. Rotation ages were estimated for the species considering four important criteria. It was observed that the rotation ages vary from 6 to 21 years for site indices 18, 15, 12, 9 and 6 meters at a reference age of 12 years. Considering the different factors of raising the coastal plantations, a rotation age of 12 years for site indices 15 and 18 meters dominant height and 15 years for site indices of 6, 9 and 12 meters dominant height at the same reference age may be prescribed for keora in the coastal plantations of Bangladesh.
In order to study the necessity for thinning and a thinning schedule for keora (Sonneratia apetala) in the plantations, data were collected from the plots laid out in Barisal and Patuakhali coastal areas. Analysis of data indicates that mortality is generally low, more age-related than density-dependent, and that thinning will affect the survival marginally. Diameter increment decreased with increasing age and increasing density. At low densities a small enhancement of diameter increment is apparent for 5 and 6-year old plantations but this marginally exceeds the natural level of variability. Thinning may be avoided by adjustment of initial spacing—increasing it from 1.2m x 1.2m to 1.75m x 1.75m.
A study was conducted at the West Virginia University Forest, U. S. A. on the effect of thinning on growth and yield of red pine during Spring, 1986. It was done by comparing two different stands, one thinned and the other unthinned. The thinned plantations received three commercial crown thinnings. The sawtimber volumes in each stand were estimated through a cruise. Sawtimber volume estimates per hectare in the thinned stand were found slightly lower than in the unthinned stand. Volumes for both the stands were then projected for next 10 years. Future sawtimber volumes were also predicted and found to be slightly higher in the thinned stand than in the unthinned one. These results were believed to have occurred because the thinning intensities were too light to prompt a better growth response at the early stage.
Physical and mechanical properties of kali (Oxytenanthera nigrociliata), mitinga (Bambusa tulda), bethua (Bamb usa polymorpha) and borak (Bambusa balcooa) have been studied at three different height positions along the culm. These properties were found to vary significantly along the culm height. The moisture content, shrinkage and bending strength decreased as the height increased, but the specific gravity, compressive strength and modulus of elasticity increased with the height. Variations of these properties were also found significant among the species. Borak bamboo exhibited the highest specific gravity and bending strength while mitinga showed the highest value in respect of compressive strength and modulus of elasticity.
Paraserianthes falcataria is a hardwood species suitable for making good quality kraft pulp with a high yield. The species is used as a raw material in one of the pulp mills in Bangladesh using soda process. Consequently, the pulp yield and quality are poor. To overcome these drawbacks this study has been conducted. The study shows that anthraquinone (AQ) has a positive effect both in soda and kraft pulping of P. falcataria. AQ addition by 0.05% can reduce the alkali charge by 5 per cent points and increase the pulp yield by about 4 per cent points in soda pulping. The yield becomes equivalent to the kraft counterpart. The use of 0.15% AQ further increases the pulp yield to surpass the kraft. But the gain in yield with 0.15% AQ addition is not as remarkable as with the lower dose (0.05%). An addition of AQ in kraft pulping also increases the yield, but not to the extent as in soda pulping. It is also observed that the pulp quality improves by the addition of AQ both in soda and kraft pulping. The soda-AQ pulp is almost equivalent to the kraft counterpart, with only 6% lower value in tearing strength at a particular tensile strength.
The so-called stem borer of moluccana koroi (Paraserianthes falcataria) has been identified as a bark-eating caterpillar, Indarbela quadrinotata Walker (Metarbelidae : Lepidoptera). The pest is polyphagous attacking many forest, shade and ornamental trees. Six new host trees were recorded for the first time. The pest has a single generation in a year. The peak infestation occurred during October- November. In 4-year old stands of P. falcataria, the mean percentage of trees infested ranged from 33.3 to 70.0 and the mean number of active larval holes per tree varied from 1.1 to 3.7. Unhealthy growing stock was most heavily infested.
Kiln drying characteristics of 2.5 cm gamar planks were studied using three types of stickers and schedules. Nine charges of gamar were run in a steamheated dry kiln. It was found that the difficulty of kiln seasoning of gamar could be eliminated substantially if an accelerated drying schedule with comparatively higher temperatures was employed in conjunction with the standard sticker thickness of 2.5 cm.
During February, 1987 a sample survey was conducted on the intensity of browsing damage by deer in a mixed plantation of 1985 under Kaptai Pulpwood Division, Chittagong Hill Tracts. A systematic strip sampling method was used for the survey. The percentages of browsed and unbrowsed plants were estimated for all the species. The estimates revealed that the plantation was almost a failure due to browsing damage by deer and early mortality of the seedlings and some other causes which could not be identified. It was found that an average of 4% plants were browsed by deer, 2% were left unbrowsed and 94% could not be traced in the plantation.
Keora is one of the most important mangrove species of the Sundarbans. It is a favoured fodder tree for mangrove wildlife. The giberralic acid content of the leaves promotes quick post larval growth of prawn and fishes (Roy Choudhuri 1990). Since 1960, keora has been considered as the main species for the coastal afforestation programmes of Bangladesh. It alone forms 67% of all planted area, amounting to 17,000 ha in the coastal area of Bangladesh (Drigo et al. 1987; Rahman et al. 1990). A serious collar rot disease of keora in the nurseries of Uttar Kattali under Chittagong Coastal Afforestation Division was observed in November, 1990. There were 750 beds of seedlings of two to three months’ old. The overall mortality of the seedlings was 10%, although some parts of the nursery were damaged heavily. The disease was also observed in the nurseries of Char Habibia, Char Alexandar and Hatia under Noakhali Coastal Afforestation Division.
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