Evaluation of Dimensional Stability of Some Selected Timber Species in Maiduguri Timber Shed
Chapter One
Objectives
Main objective
To evaluate the dimensional stability of the selected indigenous tree species planted in timber shed.
Specific objectives
- To assess growth and survival of four indigenous tree species;
- To determine basal area, volume production and mean annual increment (MAI);
- To determine stem form;
- To determine wood basic
CHAPTER TWO
LITERATURE REVIEW
Forest Plantation as Sustainable Land Use Practice
Forest plantations refer to those forest stands established by planting and/or seeding in the process of afforestation or reforestation. They are either of introduced or indigenous species that meet a minimum area requirement of 0.5 ha, tree crown cover of at least 10% of the land cover, and total height of adult trees above 5 meter (m) (Carle et al., 2002). MacDicken (2015) defined a forest plantation as a land spanning more than 0.5ha with trees higher than 5 m and a canopy cover of more than 10%, or trees able to reach these thresholds in situ. It does not include land that is predominantly under agricultural or urban land use. This definition is also accepted by FAO.
Forest plantations are grown to supply raw materials for industry and for other uses, such as fuelwood (Carle et al., 2002). Plantation forestry, with some exceptions, is substantially a land use system based either on successive rotation of plantations or on ‘new forests’ established on land often degraded by other activities including agriculture (Nambiar, 1999). Forest plantations are not natural assets in the same sense as native forests; they are assets deliberately grown, often described as tree farms, for one or more specific purpose.
Forest plantations can be categorized in single species or mixed species plantation concepts. For commercial purposes in Nigeria, many fast growing exotic species were used (Appanah and Weiland, 1993). Exotic fast growing species have been favoured in the past because the volume increments of these are high and consequently can be harvested at shorter rotations compared to indigenous tree species. However, the economic value of fast-growing exotic species is now being questioned and the potential gained from using slow-growing but higher-valued native species are looking rather more commercially and environmentally attractive (Sokhun, 2005).
Preference of Indigenous Tree Species in Various Land Uses
Indigenous tree species are not only desirable in forestry plantations but also for other land uses. So far most agroforestry interaction studies in the Sub Saharan Africa have not explored suitability of indigenous tree species (Chamshamaet al., 2006; Kimaro, 2009; Byers et al., 2012). Smallholder farmers desire to raise native trees, however, are inhibited by factors such as tenure security and insufficient knowledge and skills on propagation, management and protection (Mangaoang and Pasa, 2003). Farmers, based on perceived ecological and economic usefulness of the species, consider native trees important (Lawrence, 1997; Patindol, 1998). In Nigeria, indigenous trees and shrubs are of value in agriculture as they directly or indirectly contribute to crop and livestock production. They provide fodder to animals and replenish soil fertility unlike most exotic tree species (Komwihangilo et al., 1995).
Native trees species are commonly considered by farmers and foresters as slow growing trees, but field observations proved that in fact some of these species grow at least as fast as some exotics (Magcale-Macandog et al., 1999). Therefore the domestication of native trees is dealing with an imperfect knowledge base, since these species have often been virtually overlooked by science, and are little known commercially, except in their local areas. However, it is now recognized by the scientific community that the bias to native tree improvement needs to be readdressed by the development of novel approaches that take into consideration the requirements of small-scale, resource poor farmers and their farming systems. Given that improvement is as much a social and political challenge as a biological one, it will only be through experimental implementation of a range of approaches that methods and strategies will progress (Magcale-Macandog et al., 1999).
Selected Indigenous Tree Species
Miliciaexcelsa (Chlorophoraexcelsa) familyMoraceae
Milicia excelsais indigenous in Nigeria and other East African countries. The common name is Mvule. Ecologically it is characterized as a giant deciduous tree of lowland forest and wet savannah. The tree is logged commercially throughout its range (Mbuya et al., 1994).
CHAPTER THREE
MATERIALS AND METHODS
Collection of Samples
The wood samples of Gmelina arborea Roxb, Alstonia boonei Lam, Daniellia oliveri (Rolfe) Hutch., Antiaris toxicaria Lesch and Milicia excels (Welw.) C.C. Berg, were collected with the help of the Forest Ranger from the Forestry Department of Enugu State, Nigeria, attached to the Nsukka timber market. Preliminary identification of the samples was made following the guidelines of Titmuss and Richards [14], Anon [15], Jane [16], Desch and Dinwoodie [17], and Keay et al. [18]. A confirmatory identification of the samples was made through the microscopic studies of their sections. The features observed were compared with those given by Titmuss and Richards [14] and Desch and Dinwoodie [17].
Fifteen pieces of fresh specimens with a longitudinal dimension of 10cm and a radial dimension of 3 cm were cut from representative pieces of five timbers species. The specimens were obtained at least 500 mm (20 in.) from the end of the pieces to ensure them being free from knots and other irregularities, such as bark and pitch pockets using a BOSCH JIGSAW machine (model GST 85 PBE 580W, Germany). The samples were collected from five locations in a sheet to ensure that the sample average will accurately indicate the average of the sheet.
Determination of Moisture Content
Each specimen was weighed using Ohaus Harvard Trip Balance (Dial-O-Gram; 2KG5LB), and placed in an oven at 105°C (221°F) for 18hrs [19]. The different specimens were then soaked in tap-water for a duration of 12 hrs in which the weight of the specimen after soaking and excess water dried with a filter paper was measured at a 2hr interval. The fresh weight and the weight after drying the specimens were used to determine the percentage of moisture content before soaking using the formula:
CHAPTER FOUR
RESULTS AND DISCUSSION
The duration at which wood or furniture comes in contact with liquid water is always limited to a period, i.e either during rain, or a spill on a wooden floor. This has however necessitated the understanding of how wood responds to water over short-time periods which is very essential [20]. The different timbre species responded to change in moisture content at different rates. Generally, all the species showed a constant increase in the change in moisture content as the soaking duration increased (Table 1). The change observed across the five timber in moisture content could be summarized in the order of Gmelina aborea < Milicia excels < Daniellia oliveri < Alstonia bonnie < Antiaris toxicaria with Gmelina aborea recording significantly the lowest moisture absorbing capacity (Table 1). The cellulose and hemicellulose content of wood had been attributed to being mainly responsible for moisture uptake due to them being more hygroscopic than lignin [21].
CHAPTER FIVE
CONCLUSION AND RECOMMENDATIONS
CONCLUSION
The lower swelling coefficient and the amount of swelling observed in Milicia excels among the five timber species, makes it a more suitable species for industrial use because it would be more dimensionally stable and could be used in making durable furniture. It could be also be inferred that in order to reduce the amount of swelling in these five wood species, the wood should be dried to the proper uniform moisture content before use in manufacturing, the furniture involving these wood species should be constructed in such a way that the wood is mechanically restrained from shrinking and swelling.
Competing Interests
Authors have declared that no competing interests exist.
Recommendations
The following recommendations can be drawn from this study:-
- Conduct the same study in a replicated trial with more trees in tandem with soil characteristics will be necessary to enhance the reliability for extrapolation of the
- Construction/development of planted indigenous tree species specific allometric
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