Introduction

Trees and forests contribute substantially to a country’s socio-cultural and economic development by providing goods and services to the people. In recent decades, wood has become important raw material for forest-based industries such as sawmills, composite and plywood, pulp, and paper. Paper and pulp industries are the most vital wood-based industries worldwide, consumed in huge quantities. Global paper demand was about 402 mt annum^-1 in 2011, projected to rise to 521 million tonnes per annum by 2021 (Kulkarni, 2013). India contributes 2.6% of the world’s total paper production. The increasing demand for paper and pulp are creating pressure on natural forest. In India, most wood-based industries have been facing a shortage of raw materials, as meeting the demand is a major challenge. As a result of this predicament, industries have become reliant on imported wood products. The cost of importing timber is relatively high and time-consuming. Due to the paucity of raw materials, most paper and pulp companies have closed in recent years. The problem may be progressively handled by supporting local fast-growing tree species for wood-based industries (Kulkarni, 2013, Ghildyal, 1989). Acrocarpus fraxinifolius is an indigenous tree regarded as a potential native tree species for making plywood, planks, panel, and construction purpose with other multi-purpose services such as erosion control, fodder, gum, fuelwood, etc. (Nath et al., 2012). 

Acrocarpus fraxinifolius is a large-sized tree belonging to the family Fabaceae, commonly called Pink Cedar, as the heartwood is pinkish in color. It is locally known as Belanji and Havalige (Kannada), Mandane (Bengali), Nelarai (Tamil), Kurangadi (Malayalam) etc. It is naturally distributed in high rainfall areas in the evergreen forests of Western Ghats, Sikkim, West Bengal, and Assam. Belanji can grow up to 60 m tall with the cylindrical bole free from branches up to ¾ ^th of its total height. It is cultivated chiefly in Kodagu and Dakshina Kannada as a shade tree in coffee estates (Troup, 1921, Ghildyal, 1989, Ashwath et al., 2020, Das et al., 2022). Acrocarpus is best suitable for making plywood, planks, panel and construction, and other multi-purpose services such as fodder, gum, fuelwood, and erosion control. Wood is also a raw material for pulp and paper (Orwa et al., 2009). The leaves have lipoidal content, which exhibits an anti-inflammatory effect (Abouzeid et al., 2011). The n-hexane extract of A. fraxinifolius leaves has antihepatotoxic properties (Ghffar et al., 2017) and antioxidant and anti-inflammatory effects, which affect hyperglycemia and hyperlipidemia (Ghffer and Shehata, 2018). Belanji was considered the tree for the future because of its multi-purpose utility and recommended as one of the promising species for Agroforestry.

The quality of paper and pulp is mainly decided by the wood properties such as density, fibre, and vessel dimensions and derived indices such as Runkel ratio, slenderness ratio, flexibility coefficient, rigidity coefficient along with other physicochemical parameters (Rodriguez et al., 2017, Maiti, 2016, Maiti et al., 2016). To pulp and papermakers, a fibre of extended, tubular, cylindrical, and minimal cell derived from plants or plants’ parts are necessary with its diameter, which is just 0.1 mm, is minimal, and is thought to be tiny. However, it can range from about 0.5 mm to over 120 mm (Albert et al., 2011, Chaudhari et al., 2016, Ashwath et al., 2021). The length to diameter ratio for popular papermaking fibres ranges from 50 to 200: 1. Always, the fibers increase the quality and quantity of pulp yield, whereas the vessel elements reduce the same (Chaudhari et al., 2017, Jahan et al., 2019). The present effort mainly emphasized on the wood indices of Acrocarpus fraxinifolius for knowing the suitability for paper and pulp.

Materials and Methods

A total of 12 wood core samples were collected from trees falling under the girth class of 130 to 150 cm, standing in coffee-based agroforestry systems of Kodagu District (N 12° 06’ and E 76° 00’), Karnataka, in the month of May 2020. Wood core samples were collected using the Presseler’s increment borer at breast height level. For wood fibre analysis the core portion was divided and three, i.e., near to the pith portion, middle and periphery, and made as a composite sample. The wood samples were then macerated using Jefferys solution technique and fibre parameters (Fibre length, Fibre width, Fibre wall thickness, and Fibre Lumen width) were recorded at Forest Product and Utilization Laboratory, College of Forestry, UAHS, Shivamogga (Figure 1) (Ashwath et al., 2021). Fifty measurements on fibre parameters were recorded for each sample under a stereomicroscope with an inbuilt Image Analyzer.

To know the suitability of Acrocarpus fraxinifolius for paper making, different wood anatomical indices essential in pulp and papermaking were derived from the data obtained on fibre properties. Anatomical indices viz., Runkel ratio (Runkel, 1949), Slenderness ratio (Varghese et al., 1995), flexibility coefficient, and rigidity coefficient (Tamalang and Wangaard, 1961) were determined using the following formula.

Slenderness ratio= Fibre length/Fibre width---------------------(1)

Runkel ratio=2×Fibre wall thickness/Fibre Lumen Width-------(2)

Flexibility coefficient=Fibre lumen width/Fibre diameter×100.....(3)

Rigidity coefficient=Fibre wall thickness/Fibre diameter---------------------(4)

Results and Discussion

The quality of the paper depends on the Runkel ratio, slenderness ratio, flexibility coefficient, and rigidity coefficient (Chaudhari et al.,2017), along with the other physicochemical characteristics. The fibre anatomical ratios were derived from earlier analysis of fibre properties (Ashwath et al., 2021) to assess the suitability of species for pulp and paper. Estimated mean values of different anatomical indices of Acrocarpus fraxinifolius are presented in Table 1. The mean Runkel ratio was 0.580, the Slenderness ratio was 60.132, the Flexibility coefficient was 63.290, and the Rigidity coefficient was 0.184.

Table 1: Wood indices deciding the suitability of raw materials for paper and pulp making

The Runkel ratio of fibres must be less than one (Chaudhari et al., 2017) or in the range of 0.25 to 1.50 (Sarogoro and Emerhi, 2016). The flexibility coefficient decides the strength of the paper, which is directly associated with breaking length and tear resistance. The species having a flexibility coefficient of 50 to 75 gives an excellent paper with high strength properties (Sarogoro and Emerhi, 2016). The slenderness ratio plays a vital role in measuring the tearing strength of the paper. The species with a slenderness ratio of more than 33 is preferable in the quality of paper and pulp production (Varghese et al., 1995, Sarogoro and Emerhi, 2016). Four groups of flexibility ratios have been observed by Bektas et al. (1999) high elastic fibre (FR greater than 75), elastic (FR between 50 to 75), rigid fibre (FR between 30 to 50), and high rigid fibres (FR less than 30). The rigidity coefficient determines the stiffness of the paper. It is acceptable for paper manufacturers if the value is less than or equal to 0.5. (Tamolang and Wangard, 1961). The anatomical indices meet the parameters described in previous studies, indicating that the species may be appropriate for paper production.

The species is already being used mainly as a raw material in plywood. Pink cedar is suitable for making particleboard (Trianoski et al., 2011), preservative-treated plywood, marine, fire retardant plywood, and plywood for concrete securing grind (Shukla et al., 1993). It is also used as the core material for plywood panels (Pinati et al., 2018). Acrocarpus exhibits higher veneer yields with all strong plywood production characters (Parthiban et al., 2019). The species is reported in the production of compensated panels associated with other timber species to improve the quality of plywood (Reis et al., 2019). The resinous material in the wood characterizes Acrocarpus. These factors must be considered, along with pulping ability, cellulose yield, lignin content, and other chemical properties. Since various factors influence pulp and paper yields and quality, more studies must be conducted.

Figure 1: Measuring fibre traits

Conclusion

Timber having long fibres, slenderness ratio, flexibility coefficient, and low Runkel ratio are considered for high-quality pulp and paper production. The anatomical screening of A. fraxinifolius for pulp suggests that the species can be used as raw material for paper production besides its primary use in plywood. Further Industrial level exploration for mechanical parameters and other factors such as lignin, holocellulose, kappa number, and biochemical parameters can be assessed to know the suitability of species for paper making.

Acknowledgement

The authors would place sincere and profound gratitude and reverence on record to the College of Forestry, Ponnampet, Keladi Shivappa Nayaka University of Agricultural and Horticultural Sciences, Shivamogga, for lab facilities and opportunity. The authors also announce that there is no conflict of interest.

Albert, S., Padhiar, A., Gandhi, D., 2011. Fiber properties of sorghum halepense and its suitability for paper production. Journal of Natural Fibers 8(4), 263–271.

Ashwath, M.N., Sathish, B.N., Deepthi, N.L., Devagiri, G.M., Hegde, R.K., Hareesh, T.S., 2021. Geographic and within tree variation for wood properties in Acrocarpus fraxinifolius wight and arn. populations. Journal of Scientific and Industrial Research 80(12), 1049–1055.

Ashwath, M.N., Satish, B.N., Devagiri, G.M., Hegde, R.K., Hareesh, T.S., 2020. Variation in growth traits of Acrocarpus fraxinifolius wight and arn. populations in Southern Karnataka, India. International Journal of Current Microbiology and Applied Science 9(8), 1838–1843.

Bektas, I., Tutus, A., Eroglu, H., 1999. A study of the suitability of Calabrian pine (Pinusbrutia Ten.) for pulp and paper manufacture. Turkish Journal of Agriculture and Forestry 23(EK3), 589–598.

Chaudhari, P., Sohagiya, N., Sinha, S., Jha, S., Thakur, N., 2016. Wood anatomical screening of eucalyptus genotypes for high-quality pulp and paper making. In: Forest and tree-based land use systems for livelihood, nutritional and environmental security, Navsari, Gujrat, 152.

Chaudhari, P.A., Sohagiya, N.J., Sinha, S.K., Thakur, N.S., Jha, S.K., 2017. Wood anatomical screening of short rotation trees for pulp and paper making properties: A review. In: Parthiban, R., Seenivasan R. (Eds.), Plantation and agroforestry: Pulpwood value chain approach, Scientific Publisher, 102–08.

Das, P.K., Sahoo, T., Kamila, P.K., Panda, P.C., 2022. Acrocarpus fraxinifolius Arn. (Leguminosae-Caesalpinioideae), a tree species new to flora of Odisha. Species 23(71), 161–164.

Ghildyal, B.N., 1989. Introduction of Acrocarpus fraxinifolius-a fast growing species for social forestry in Himachal Pradesh. Indian Forester 115(7), 455–458.

Jahan, M.S., Haque, M., Quaiyyum, M.A., Nayeem, J., Bashar, M.S., 2019. Radial variation of anatomical, morphological and chemical characteristics of Acacia auriculiformis in evaluating pulping raw material. Journal of the Indian Academy of Wood Science 16(2), 118–124.

Kulkarni, H.D., 2013. Pulp and paper industry raw material scenario-ITC plantation a case study. IIPTA25(1), 79–90.

Maiti, R., 2016. Wood anatomical structure could determine wood quality and its utilization: a hypothesis. International Journal of Economic Plants 3(2), 46–48.

Maiti, R., Rodriguez, H.G., Diaz, J.C.G., Tijerina, H.A.D., Flores, A.A.C., Kumari, A., Sarkar, N.C., 2016. Comparative wood anatomy of 20 woody plant species in northeastern Mexico and its significance. International Journal of Bio-resource and Stress Management 7(2), 229–246.

Orwa, C., Mutua, A., Kindt, R., Jamnadass, R., Simons, A., 2009. Agroforestree database: a tree reference and selection guide. Version 4. Agroforestree Database: a tree reference and selection guide. Version4.

Parthiban, K.T., Dey, S., Krishnakumar, N., Das, A., 2019. Wood and plywood quality characterization of new and alternate species amenable for composite wood production. Wood Fiber Science 51(4), 1–8.

Pinati, E., Faria, D.L., Mendes, R.F., Mendes, L.M., Protasio, T.D.P., GuimaraesJunior, J.B., 2018. Blockboard plywood produced from Pinusoocarpa, Castillaulei and Acrocarpus fraxinifolius. Ciencia Da Madeira 9(3), 199–208.

Reis, A.H.S., Silva, D.W., Vilela, A.P., Mendes, R.F., Mendes, L.M., 2019. Physical-mechanical Properties of Plywood Produced with Acrocarpus fraxinifolius and Pinusoocarpa. Floresta e Ambiente 26(4),e20170157.

Rodriguez, H.G., Maiti, R., Diaz, J.C.G., 2017. Comparative wood anatomy of twelve woody plant species in northeastern Mexico and its relation to taxonomy and wood quality. International Journal of Economic Plants 4(1), 1–9.

Runkel, R.O., 1949. Uber die Herstellung von ZellstoffausHolz der Gattung Eucalyptus and Versuche mit zwei unterschiedlichen Eucalyptusarten. Das papier 3, 476–490.

Sarogoro, N., Emerhi, E.A., 2016. Runkel, flexibility and slenderness ratios of Anthocleista djalonensis (A) wood for pulp and paper production. African Journal of Agriculture, Technology and Environment 5(2), 27–32.

Shukla, K.S., Sharma, R.C., Anil, N., 1993. Suitability of Acrocarpus fraxinifolius (mundani) for plywood. Journal of the Timber Development Association of India 39(4), 39–45.

Tomolang, F.N., Wangaard, F.F., 1961. Relationships between hardwood fiber characteristics and pulp properties. Tappi 44(3), 201–216.

Trianoski, R., Iwakiri, S., deMatos, J.L.M., Prata, J.G., 2011. Feasibility of using of Acrocarpus fraxinifolius in different proportions with Pinustaeda for production of particleboard. Scientia Forestalis 39(91), 343–350.

Troup, R.S., 1921. Silviculture of Indian trees, Asiatic Publishing House, Delhi, 338–341.

Varghese, M., 1995. Genetic effects on wood and fibre traits of Eucalyptus grandis Provenances. In Proceedings of CRCTHF-IUFRO Conference, Eucalypt Plantations: Improving Fibre Yield and Quality, Hobart.