Occurrence and anatomical features of growth rings in tropical rainforest trees in Peninsular Malaysia: a preliminary study

The occurrence and anatomical features of growth rings were investigated in tropical tree species in Peninsular Malaysia. The species studied included five species from two plantations, in a tropical monsoon and tropical rainforest climate, and 26 species from a natural forest in a tropical rainforest climate. Most of the trees were diffuse-porous species, with the exception of Peronema canescens, which was ring-porous. The growth rings were observed macroscopically and microscopically and were classified as having fiber zones, radially flattened fibers, marginal parenchyma, thick-walled fibers, or variations in vessel size and density. Whereas P. canescens from two plantations and Intsia palembanica from the natural forest showed well-defined growth rings, possibly formed annually following environmental stresses, 17 species showed indefinable growth rings and 10 species had no growth rings. Many of the samples presented intermittent growth rings, ambiguous growth rings, discontinuous growth rings, or resin canals and/or traumatic canals that made them difficult to classify. Bands of axial parenchyma were observed macroscopically in Sindora wallichii and Azadirachta excelsa, but microscopic analysis revealed that these bands were formed by concentric traumatic canals. Parenchyma bands with resin ducts or traumatic canals were likely not to be formed periodically. We concluded that some tree species that grow in a tropical rainforest climate do form growth rings and may be used in tree-ring analysis studies

Cambial activity of Dipterocarpus costulatus in relation to different stem diameters and climate factors

This study investigated the seasonal cambial activity in Dipterocrpus costulatus trees with different range of stem diameter at breast height (dbh). Samples from main stem of D. costulatus with dbh 15 cm and 25 cm growing in natural lowland dipterocarp rainforest of west Peninsular Malaysia were collected for this purpose. Collections of cambial samples were carried out in 2-month intervals from August 2010 till June 2011. Cambial activity was determined by counting the numbers of cambial and expansion zone cell layers towards the outer sapwood. A greater number of cell layers indicated greater cambial activity. Results showed that the cambium of trees with dbh 15 cm were influenced by the amount of rainfall. However, cambium of trees with dbh 25 cm showed relatively less sensitivity to rainfall. Dipterocrpus costulatus showed active and inactive phases during the observation period. Thus, this study has proven that this species did not grow continually at the same rate in natural forests. Instead it showed periods of alternate active and inactive growth

Estimation of tree age in the humid tropics by vessel measurement: a preliminary study

We estimated the age of plantation-grown trees lacking distinct and consistent annual rings to examine whether an anatomical method for determining the vessel traits of wood is effective in the tropical rain forest climate. Stem disks from 1 Dipterocarpaceae and 2 Meliaceae species for which the planting year was known were collected, and radial strips were sawn out from 2 different radii on each disk. We measured mean vessel lumen area (MVLA) and vessel frequency (VF) and found that radial changes in the 2 variables showed cyclic variation in all samples. The cycle number of both MVLA and VF mostly matched the tree age when they were analyzed with proper radial resolution. The number and shape of the cyclic variations were different between the 2 radii; this inconsistency could partly be ascribed to asynchronous cambium activity. The result implies that (1) the selection of sample species is important and (2) more than 1 radius should be analyzed to increase the accuracy of estimation. Thus, we concluded that vessel traits are important growth-ring indicators in the humid tropics, but a single application of this method of ring analysis may not be sufficiently accurate in age estimation. Further research on the factors affecting vessel formation will make the method more effective

Effectiveness of online teaching and learning of wood science and technology courses during the COVID-19 pandemic: early evidences from a survey of Malaysian Universities

Wood Science and Technology (WST) courses have been traditionally taught face-to-face in most of the universities worldwide, but the global COVID-19 pandemic has disrupted classroom lessons, replacing them with online teaching and learning methods. To assess the effectiveness of these online methods, a survey of students and academics were carried out in several Malaysian universities offering the WST programs. The survey revealed that students were mostly challenged by the problems related to access to internet, computer hardware, and lack of communication. Further, the student-centered learning method was preferred, while non-technical courses were the most suited for online teaching and learning. In contrast, academics appear to prefer pre-recorded lectures and recorded videos as the most common method for teaching online, while continuous assessment of the student’s progress found limited application. The results found that to enhance the effectiveness of teaching and learning online of WST courses, factors such as connectivity, student’s preparedness, content design, pedagogical approach, peer communication, and the teacher’s presence, must be taken into consideration and improved

半島マレーシアの熱帯林樹種における成長輪形成

京都大学0048新制・課程博士博士(農学)甲第18338号農博第2063号新制||農||1023(附属図書館)学位論文||H26||N4845(農学部図書室)31196京都大学大学院農学研究科森林科学専攻(主査)教授 大澤 晃, 教授 髙部 圭司, 教授 北山 兼弘学位規則第4条第1項該当Doctor of Agricultural ScienceKyoto UniversityDFA

Vessel feature changes as a tool for detecting annual rings in tropical trees

Radial variations in vessel features (vessel lumen area and frequency) of four tropical tree species grown in tropical savanna, monsoon, and rainforest climates were investigated to detect indistinct annual rings. Leaf and soil water potentials were measured periodically to show annual variations in water availability and their relationship to radial variations in vessel features. In addition, the accuracy of annual-ring detection was estimated using trees of known age. Radial variations in vessel features showed annual cyclicity in all three sites. The vessel feature that showed clear annual cyclicity was different among the species and sites. Furthermore, the variation pattern of vessel features in the rainforest site tended to be different between two radii within individual trees, implying low synchronicity of wood formation in the wet area. Compared with leaf and soil water potentials, vessel features varied independent of water availability in all species in the rainforest site and most species in the savanna and monsoon sites. The direct effect of low water availability on vessel features was considered only in one species in the savanna and monsoon sites. Nevertheless, the deviation of vessel feature cycles from tree age was similar and reasonably small (mostly within ±10 %) among all sites. These results indicated a circannual rhythm in vessel formation. Thus, vessel feature changes seemed to aid in detecting annual rings in trees throughout wide tropical areas; however, asynchronous wood formation must be considered in dendrochronology, especially in humid tropics

Effectiveness of Online Teaching and Learning of Wood Science and Technology Courses during the COVID-19 Pandemic: Early Evidences from a Survey of Malaysian Universities

Wood Science and Technology (WST) courses have been traditionally taught face-to-face in most of the universities worldwide, but the global COVID-19 pandemic has disrupted classroom lessons, replacing them with online teaching and learning methods. To assess the effectiveness of these online methods, a survey of students and academics were carried out in several Malaysian universities offering the WST programs. The survey revealed that students were mostly challenged by the problems related to access to internet, computer hardware, and lack of communication. Further, the student-centered learning method was preferred, while non-technical courses were the most suited for online teaching and learning. In contrast, academics appear to prefer pre-recorded lectures and recorded videos as the most common method for teaching online, while continuous assessment of the student’s progress found limited application. The results found that to enhance the effectiveness of teaching and learning online of WST courses, factors such as connectivity, student’s preparedness, content design, pedagogical approach, peer communication, and the teacher’s presence, must be taken into consideration and improved