Evaluation of Physical Properties of Some Selected Bambusa Species of Manipur

Bamboo is one of the most important Non Timber Forest Products of India and is the best substitute of wood these days due to depletion of wood resources. Bamboos belong to family Poaceae and subfamily Bambusoideae (Zakikhani et al., 2017). They grow luxuriantly in the tropical and subtropical regions of the world except Europe and Antarctica. As compared to wood, it has fast growth, easy to propagate and has higher tensile strength. They are commonly exploited for multipurpose uses such as scaffoldings, basketry, handicrafts, furniture, cutlery, etc. (Chaowana, 2013).

Physical properties are known to determine the strength and desirability of bamboos. Mechanical characteristics of a bamboo are directly proportional to its physical properties. Few authors have worked on the physical properties of some Bambusa species. Kamruzzaman et al., (2008) studied moisture content, density and shrinkage of different ages of Bambusa balcooa, B. tulda and B. salarkhanii at different height positions. Kumar et al., (2015) also studied the above physical properties such as moisture content, specific gravity and dimensional shrinkage of Bambusa mizorameana along and across the culm height. Abdullah et al., (2017) examined the density and its relation to morphology and macro structures viz. vascular bundle and parenchyma of Bambusa vulgaris Schrad var. Vittata. Krishnakumar et al., (2017) analyzed and compared the moisture content, basic and bulk density of Bambusa balcooa and Bambusa vulgaris harvested from five agro-climatic regions of Tamil Nadu, India. Nordahlia et al., (2019) investigated the density and shrinkage of B. blumeana, B. heterostachya, B. vulgaris and B. vulgaris cv. Vittata along culm height for determining their suitability for end uses. 

A total of 125 indigenous and 11 exotic species under 23 genera of bamboos are reportedly spread in the deciduous and semi-evergreen forests of North-eastern region and tropical moist deciduous forests of Northern and Southern India (Anonymas, 2021). Bambusa, Dendrocalamus and Ochlandra constitute the three largest bamboo genera in India (Sharma and Nirmala, 2015). There are 130 species of Bambusa genus in the world (Das et al., 2013), out of which around 37 species and 2 varieties of Bambusa are available in India (Sharma and Nirmala, 2015). In Manipur, genus Bambusa is represented by 9 species (Naithani et al., 2015). Bamboo has been an integral part of people’s lives of Manipur. The most common uses of bamboo in the state are house constructions, roofing, bamboo reinforced mud wall, flooring, doors and windows, etc. Bambusa tulda and B. kingiana are commercially important species in the valley used as scaffolding, pandal making, agricultural implements and baskets. Fine bamboo splits or “Peiya” which are made from B. nutans are used in many ritual practices by the Meitei people of Manipur. B. ventricosa and B. vulgaris are cultivated as ornamental plants due to its aesthetic value. Although, there has been some investigations carried out on bamboos of Manipur (Rajkumari and Gupta, 2013; Naithani et al., 2015), information on physical properties of Bambusa species of the state is very limited. Therefore the present evaluation was executed in order to provide the detailed account of physical properties of some selected Bambusa species of Manipur and their variations along the culm height.

The study was conducted in the year 2019-2021 at Wood Science and Forest Products Laboratory, Department of Forestry, North Eastern Regional Institute of Science and Technology (NERIST), Arunachal Pradesh. Eight species of Bambusa viz., Bambusa balcooa Roxb., B. binghamii Gamble, B. kingiana Gamble, B. multiplex (Lour.) Raeusch. ex Schult. f., B. nutans Wall, B. tulda Roxb., B. vulgaris Schrad. ex J.C. Wendl. and B. ventricosa McClure were collected from various parts of Bishnupur, Imphal East, Imphal West and Thoubal districts of Manipur (Fig 1). The geographical co-ordinates and elevations are given in Table 1.  The mentioned districts are humid subtropical plain areas of the state. Rivers namely Nambul, Khuga, Imphal, Iril, Sekmai and Thoubal flow though this plain area. Many lakes and swamps are found in this region. Loktak Lake, the largest freshwater lake of India is located at Moirang of Bishnupur district. Climate is temperate with an average temperature ranging from 1 to 2°C in winter and 32 to 33°C in summer. Average annual rainfall ranges from 1200 to 1400 mm. Soil is fertile, well-drained, clayey loam, acidic (pH ranging from 4.5 to 5.5) in Bishnupur, Imphal West and Thoubal while it is slightly acidic in Imphal East. Vegetation consist of medicinal herbs, spices, rice crops, shrubs, bamboos and trees such as Ficus religiosa (Pipal),  Eucalyptus globulus (Eucalyptus), Phyllanthus emblica (Amla), Parkia roxburghii (Yongchak), Arundo donax (yendhou), Carica papaya (papaya), Citrus maxima (Pomelo), Mangifera indica (Mango), Prunus domestica (plum), Prunus persica (peach), Pyrus serotina (pear), Psidium guajava (guava), Tamarindus indica (Tamarind), etc. Five matured culms of each species were harvested at 30cm above the ground level. The upper lofty portions were discarded; the end portions of the remaining culms were painted to reduce sap evaporation and brought to laboratory for further studies. The length of culms, number of internodes, their lengths and diameter were measured at the site itself. The morphological parameters of these selected Bambusa species are given in Table 2. These culms were further divided into equal lengths from bottom, middle and top height positions. Rings of 2.5 cm height were cut from the internodal regions of all the three height positions for each species. Further, sample strips were prepared from these rings.  A total of 105 strips were taken separately for the determination of each physical property.





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Determination of moisture content, specific gravity and dimensional shrinkage percentage (longitudinal, radial and tangential) were carried out using Indian Standard Method IS 6874 (2008).

Water absorption percentage was determined by following ASTM D 1034-72 method.

The data were analysed by using SPSS software 16.0 at α = 0.05.  One way analysis of variance (ANOVA) followed by Tukey’s test was carried out to compare the mean values of physical properties among the selected species.

Moisture content and water absorption capacity of bamboo are important parameters of bamboos which govern its durability/life span. Bamboos with high moisture content are susceptible to fungal and insect attacks. Both moisture content and water absorption percentages decreased from bottom to top along the culms in all the species. Similar observations were reported in other bamboo genera by different workers (Razak et al., 2006; Kamruzzaman, et al., 2008; Bhonde et al., 2014; Zakikhani et al., 2014). Wakchaure and Kute, 2012 also found that the moisture content percentage and water absorption was not constant along the culm height. They further added that these parameters varied with age and height of bamboos. Among the species, the moisture content was observed maximum in culms of B. multiplex (66.88%) whereas B. vulgaris showed maximum water absorption (84.60%). Both moisture content and water absorption were observed minimum in B. nutans (42.67% and 56.36%). These differences are also dependent on the species, geographical location of the collected bamboo as well as the season of felling. There are variations in anatomical structures of bamboo species which may be the probable reason for maximum and minimum moisture content and water absorption in these species. The culm wall thickness decreased from bottom to top in all bamboo species. Larger vascular bundles with higher percentage of parenchyma are generally present at the bottom and middle positions of culms. This results in the highest moisture content and water absorption at these heights. Water absorption depends on the percentage of porosity and presence of intercellular spaces which is different for every bamboo species.

Specific gravity or basic density of bamboo determines the strength of bamboo. It varies with age, vertical culm height as well as horizontally across the culm wall/ B. ventricosa (0.65) showed the maximum average specific gravity while the minimum average specific gravity was shown by B. vulgaris (0.52). Specific gravity increased from bottom towards the top in all species. The results are similar to the findings of Falayi and Soyoye, 2014; Sharma et al., 2019 and Selvan et al., 2017. The reason for the increase of the specific gravity at top height position is due to decrease in the culm wall thickness which results in compactness of highly thick walled sclerenchymatous fibrous tissue with less percentage of parenchyma (Sharma et al., 2017). Santoshkumar and Bhat, 2014 reported that the increase in specific gravity/basic density along the culm height is indicative of higher proportion of fibrous tissues and higher frequency of vascular bundles at top position of bamboos. The relation of specific gravity with anatomical structure and chemical constituents influence the pattern in specific gravity in different bamboo species. The specific gravity also varies with variation in bamboo species (Abd. Latif and Jusoh, 1992).

Loss of water molecules bound to cell wall of bamboos results in shrinkage which further determines its dimensional stability (Aguinsatan et al., 2019). Bamboo, like wood is also an anisotropic material and its properties are different in longitudinal, radial and tangential directions. These variations in result may be due to difference in the size and proportion of xylem elements present at different height positions of these species. Longitudinal shrinkage was lesser than radial and tangential shrinkage in all Bambusa species (Table 3). Similar observation was reported in Phyllostachys bambusoides by Sharma et al., (2019). Longitudinal shrinkage was minimum in all species and ranged from 0.78% (B. kingiana) to 2.81% (B. binghamii). Radial shrinkage was higher than tangential shrinkage because bamboo is a monocotyledon and rays are absent. There is no specific pattern of variation in longitudinal, radial and tangential shrinkage from bottom to top in culms of Bambusa species. B. binghamii and B. tulda showed higher shrinkage towards the bottom and decreased gradually towards the top. Likewise, other workers reported higher shrinkage percentages at the bottom height position (Kamruzzaman et al., 2008; Sompoh et al., 2013). This may be probably due to the presence and loss of higher initial moisture content at the base portion. While the top portions of B. balcooa, B. multiplex and B. ventricosa exhibited higher shrinkages (radial, longitudinal and tangential) than the middle and bottom. On the contrary, B. kingiana and B. vulgaris showed that their middle portion had maximum dimensional shrinkages. These variations in result may be due to difference in the size and proportion of xylem elements present at different height positions of these species. The variation in tangential shrinkage can be related to the bamboo’s anatomical structure and density (Anwar et al., 2005). The dimensional stability in bamboo depends on its volumetric shrinkage and T/R ratio as in wood. Volumetric shrinkage is the sum of radial and tangential shrinkage. T/R is a good indicator of dimensional stability and measures the uniformity of shrinkage in bamboos (Panshin and de Zeeuw, 1980). Bamboos with good stability have low volumetric shrinkage and low T/R ratio. On the basis of volumetric shrinkage, Calderon (2012) classified bamboos into three categories namely low shrinkage (VS£11.5%), medium shrinkage (VS 11.5%-14.5%) and high shrinkage (VS³14.0%). According to this classification, B. balcooa, B. kingiana, B. nutans, B. ventricosa are low shrinkage bamboo, B. multiplex is medium shrinkage bamboo while B. binghamii, B. tulda and B. vulgaris are high shrinkage bamboos. The results given in Table 5 showed that T/R ratio in all Bambusa species varied from 0.61 (B. balcooa) to 1.29 (B. nutans). Whereas in case of wood, T/R ratio varies from 1-3. The present study reveals that all Bambusa species shrink uniformly and are dimensionally stable.







The results for analysis of variance (ANOVA) for all physical properties among eight Bambusa species tabulated in Table 4 exhibited a significant variations at all height positions.

Moisture content and water absorption percentages decreased along the culm height in all species. Specific gravity of all Bambusa species increased from bottom to top portion. Radial and tangential shrinkages were higher than longitudinal shrinkage. Longitudinal shrinkage did not exhibit a definite pattern. All the physical properties showed significant variations at bottom, middle and top positions. B. kingiana is the most desirable species based on the study results considering the comparatively higher specific gravity and low moisture content, water absorption capacity, dimensional shrinkage and T/R ratio.

The first author is thankful to DST for financial assistance as an Inspire Fellow. The authors are thankful to Director, NERIST, Nirjuli-791109, Arunachal Pradesh for providing required laboratory facilities.