Showing papers in "Iawa Journal in 1995"
TL;DR: Dendrochronological methods applied to carefully prepared samples can serve as proof of the annual periodicity of growth zones and the analysis of stable isotopes in rings of tropical trees promise to provide interesting climatological information.
Abstract: Cambial dormancy and annual rings in tropical trees are induced by annually occurring dry periods or flooding. Growth periodicity is indicated by the leaf fall behaviour and is connected with an annual periodicity of shoot elongation. Changes in stem diameter are measured with a dendrometer or by measurable differences in the electrical resistance of the cambium. Dendrochronological methods applied to carefully prepared samples can serve as proof of the annual periodicity of growth zones. For this purpose the following methods have been used: cambial wounding, radiocarbon dating, pointer year detection and regression analyses of ring width and climate data. Although X-ray densitometry and the analysis of stable isotopes in rings of tropical trees promise to provide interesting climatological information, the use of these methods remains difficult.
350 citations
TL;DR: There is some promise that the whole network of teak chronologies in northern Thailand can contribute to reconstructing climate over at least the last three centuries.
Abstract: From a network of teak chronologies in northern Thailand, 75 trees within one province were evaluated regarding their climatic signal. The raw tree-ring series revealed a high mean sensitivity of 0.50 and a moderate first-order autocorrelation of 0.48. The first principal component of the standardized data explained 44% of the total variation in the tree-ring data, indicating a considerable climatic influence on tree growth. The climate-growth relationship suggested that growth of teak in this study area is mainly controlled by rainfall from April to June. Thus, there is some promise that the whole network of teak chronologies in northern Thailand can contribute to reconstructing climate over at least the last three centuries.
111 citations
TL;DR: Some of the first tree-ring chronologies from mainland Southeast Asia have been developed from Thailand, and a significant link between climate and tree growth has been suggested, and the dendrochronological potential of another species, the long-lived Podocarpus neriifolius, is discussed.
Abstract: Some of the first tree-ring chronologies from mainland Southeast Asia have been developed from Thailand, and a significant link between climate and tree growth has been suggested. Four chronologies from two species of pine (Pinus kesiya Royle ex Gordon and Pinus merkusii Jungh. ' de Vriese) from northeastern, lower northern and northwestern Thailand have been constructed: three from P. kesiya and one from P. merkusii. A second P. merkusii chronology is being developed from samples from northwestern Thailand. Preliminary climate modelling demonstrates significant relationships for tree growth with both temperature and precipitation for both species. A significant, direct relationship is revealed with temperature at the beginning of the wet season for Pinus merkusii from Thung Salaeng Luang National Park, along with an inverse relationship with precipitation for the same period. It is also suggested that the month of November (the transitional month from wet to dry season) during the year of growth is most important for Pinus kesiya from Nam Nao National Park, based on significant, direct relationships with both temperature and precipitation. The dendrochronological potential of another species, the long-lived Podocarpus neriifolius, is also discussed.
80 citations
TL;DR: The results of investigations at the Oxford Forestry Institute on the occurrence of seasonal growth rings in the wood of one of Africa's most widely distributed genera in the arid areas, Acacia are summarized.
Abstract: This paper reviews and summarizes the results of investigations at the Oxford Forestry Institute on the occurrence of seasonal growth rings in the wood of one of Africa's most widely distributed genera in the arid areas, Acacia. The ring boundaries are marked by fine marginal parenchyma containing small crystals of Ca-oxalate. Rings are usually annual and produced in the rainy season. Ring width is related to precipitation and/or minimum temperature. Rooting characteristics of the various species studied influence the type of relationship found.
65 citations
TL;DR: Several plant communities in central Panama contain trees with annual growth rings, i.
Abstract: Several plant communities in central Panama, each community located near a weather station, contain trees with annual growth rings, i. e. Cordia alliodora, Pseudobombax septenatum, and Annona spraguei. Tree-ring data are particularly valuable when concomitant weather information is readily available. Patterns of growth for the above species of trees were investigated across central Panama in relation to climate. A linear aggregate climate model was fitted to chronologies of each species at three sites along a rainfall gradient. Comparisons were made among sites to help explain how climate influences tree growth within central Panama.
62 citations
TL;DR: Wood formation in the two tree species appears to be a continuous process and not related to seasonality in rainfall and phenology.
Abstract: The wood formation of kapur (Dryobalanops sumatrensis) and tembaga (Shorea leprosula), growing under a weak seasonal climate in West Malaysia was studied over a four-year period using cambium marking. Technical problems arose from the heavy callus formation due to the wounding of the cambium, the small radial increment, and the high variability of the cambial activity around and along the stem. Wood formation in the two tree species appears to be a continuous process and not related to seasonality in rainfall and phenology.
62 citations
TL;DR: Morphological and anatomical responses of Alnus japonica seedlings to flooding are discussed and Ethylene production in the submerged portions of stems was greatly increased by flooding.
Abstract: Flooding of soil of potted, 24-month-old Alnus japonica seedlings for 24 days altered growth, morphology, stem anatomy, and ethylene production. This species exhibited high adaptability to soil flooding by forming adventitious roots that grew through hypertrophied lenticels. Aerenchyma tissues were observed in the bark of the adventitious roots. Flooding slightly reduced height growth and greatly stimulated diameter growth of submerged portions of stems in comparison with unflooded seedlings. Diameter growth in flooded seedlings was largely due to increases in both the number and size of wood fibres produeed during the flooding period. Flooding did not affect biomass increment of leaves and stems but reduced the total dry weight increment of the root system even though abundant adventitious roots had formed. Ethylene production in the submerged portions of stems was greatly increased by flooding. Morphological and anatomical responses of Alnus japonica seedlings to flooding are discussed.
52 citations
TL;DR: The results suggest that E. grandis × nitens may be more water use efficient than E.grandis, which is commonly grown for timber and thus could potentially be used as a replacement species that is more water conservative in this water limited region.
Abstract: The primary objective of this study was to determine the relationships between water availability, plant growth and selected vessel characteristics for Eucalyptus grandis and two hybrids, so as to ascertain whether these xylem characteristics predict water use efficiency. Cuttings of Eucalyptus grandis, E. grandis × camaldulensis and E. grandis × nitens were planted in 220 litre drums from which rainfall was excluded. One half of the individuals received a low watering treatment; one half received a higher watering treatment. Soil moisture depletion through root uptake was monitored weekly and the removed water replaced to maintain 60 and 80 litres in the pots of the low and high watering treatments respectively. Mean values for tangential vessel diameter, vessel frequency and vessel element length were compared for the two treatments. In E. grandis and the hybrid E. grandis × camaldulensis vessel diameter (P < 0.01 ' P < 0.05 respectively) and vessel element length (P < 0.05 for both) increased from the dry to the wet treatment as water uptake through transpiration increased. There is no significant correlation between available water and vessel frequency. For E. grandis × nitens, on the other hand, only vessel frequency was significantly (P < 0.01) correlated with water uptake. In all three species/hybrids water availability also had a significant influence on stem diameter (P < 0.0001) and transverse sectional stem area (P < 0.0001) which increased with increased water consumption. These results suggest that E. grandis × nitens may be more water use efficient than E. grandis, which is commonly grown for timber and thus could potentially be used as a replacement species that is more water conservative in this water limited region.
51 citations
TL;DR: Dicotyledonous woods were more diverse in the Cretaceous than in the Paleocene of the San Juan Basin, and some combinations of features represent strategies of the hydraulic system that are extremely rare in the Tertiary and at present.
Abstract: Fossil wood is common in the Late Cretaceous and Early Paleocene of the San Juan Basin, New Mexico. Six types of dicotyledonous wood are recognized: Paraphyllanthoxylon arizonense Bailey, Paraphyllanthoxylon anasazi sp. nov., Plataninium piercei sp. nov., Metcalfeoxylon kirtlandense gen. et sp. nov., Chalkoxylon cretaceum gen. et sp. nov., Carlquistoxylon nacimientense gen. et sp. nov. Woods with the characteristics of Paraphyllanthoxylon arizonense Bailey are the most common and occur in the Cretaceous Kirtland Shale and the Paleocene Ojo Alamo Sandstone and Nacimiento Formation. This wood type's characteristics are stable from the Cretaceous to the Paleocene. There were no significant differences in the vessel diameters, vessel densities, ray sizes, or estimated specific gravities of the P. arizonense woods from the Late Cretaceous (Kirtland Shale) and Early Paleocene (Nacimiento Formation and Ojo Alamo Sandstone). Based on the samples examined for this study, dicotyledonous woods were more diverse in the Cretaceous (five types) than in the Paleocene (two types) of the San Juan Basin. Diameters of the Cretaceous woods examined ranged from 14-40cm indicating they were trees rather than shrubs; diameters of the Paleocene woods examined ranged from 10-80cm. All the woods have generalized structure with combinations of features seen in more than one extant family, order, or subclass. Information from databases for fossil and extant woods indicates that some combinations of features (e. g., solitary narrow vessels, low vessel density and scalariform perforation plates, as seen in Metcalfeoxylon kirtlandense and Chalkoxylon cretaceum), while relatively common in the Cretaceous, represent strategies of the hydraulic system that are extremely rare in the Tertiary and at present. None of the dicotyledonous woods have distinct growth rings, although some samples of Paraphyllanthoxylon arizonense from the Paleocene show variations in vessel density and vessel diameter that may correspond to seasonal variations in water availability.
48 citations
TL;DR: Diameter growth of both species was greatest in the rainy season and decreased in the dry season, and cambial initials at the time of pinning was estimated in the zone where cells were indirectly affected by the pinning and continued their physiological activity resulting in the formation of aberrant cells.
Abstract: Seasonal characteristics of wood formation were investigated using the pinning method in Hopea odorata and Shorea henryana in a natural dry evergreen forest of eastern Thailand. The position of cells having initiated S1-layer formation at the time of pinning was estimated in the zone where cells were directly injured by the pinning and consequently destroyed. The position of cambial initials at the time of pinning was estimated in the zone where cells were indirectly affected by the pinning and continued their physiological activity resulting in the formation of aberrant cells. Traumatic resin canals were occasionally formed in Shorea. These canals were formed after pinning and could, therefore, not record the exact time of the pinning. Diameter growth of both species was greatest in the rainy season and decreased in the dry season.
41 citations
TL;DR: A secondary thickening meristem is recorded for the first time in someherbaceous taxa of Asparagales (Herreria montevidensis and Thysanotusspiniger) and the new records are assessed in a systematic context.
Abstract: A secondary thickening meristem is recorded for the first time in someherbaceous taxa of Asparagales (Herreria montevidensis and Thysanotusspiniger), and the new records are assessed in a systematic context.
TL;DR: Although the fossil wood shares a number of characteristics with the Podocarpaceae, it differs from any existing genera and is described as a new taxon, Jeffersonioxylon gordonense.
Abstract: Wood from an in situ permineralized forest from the Middle Triassic of Gordon Valley (Queen Alexandra Range, central Transantarctic Mountains) in Antarctica is described as a new taxon, Approximately 100 trunks in growth position are present at the site; they range from 13-61 cm in diameter and suggest that some of the trees were up to 20 m tall, Pits in the radial walls of the tracheids are of the abietinean type, Rays are uniseriate and 1-9 cells high; cross fields include one to two pits that appear to be simple, Axial parenchyma is absent. Pith and cortex are not preserved. The Antarctic wood is compared with existing fossil wood types from Antarctica and other parts of Gondwana. Although the fossil wood shares a number of characteristics with the Podocarpaceae, it differs from any existing genera and is described as a new taxon, Jeffersonioxylon gordonense.
TL;DR: The wood anatomy of 31 Schefflera species from Indochina, Australia, Oceania, Africa, and South America, 3 species of Didymopanax from SouthAmerica, and Tupidanthus calyptratus andScheffleropsis hemiepiphytica from Ind Vietnam are described.
Abstract: The wood anatomy of 31 Schefflera species from Indochina, Australia, Oceania, Africa, and South America, 3 species of Didymopanax from South America, and Tupidanthus calyptratus and Scheffleropsis hemiepiphytica from Indochina (Araliaceae) are described. Seven groups of species can be recognised.
TL;DR: Six plantation grown Kelempayan trees were sampled along their radii and at five different height levels to evaluate variations of wood anatomical properties, indicating that between tree differences in all anatomical properties measured were significant.
Abstract: Six plantation grown Kelempayan trees [Neolamarckia cadamba (Roxb.) Bosser, syn. Anthocephalus chinensis (Lamk.) A. Rich. ex Walp., Rubiaceae] were sampled along their radii and at five different height levels to evaluate variations of wood anatomical properties. Analysis of variance indicates that between tree differences in all anatomical properties measured were significant. Vessel proportion increases while ray proportion decreases with height, while both fibre diameter and fibre lumen diameter decrease with height. No significant trend was found for fibre length vertically. Cell wall substance and vessel and ray proportion increase from pith to bark, while fibre proportion decreases. Fibre length and fibre wall thickness increase from pith to bark, while fibre diameter and fibre lumen diameter first increase and then decrease. Within-tree variations are more consistent radially than vertically.
TL;DR: DNA data as weIl as maeromorphologie al data implicate Saururaeeae, along with Aristolochiaceae, Lactoridaceae, and Piperaceae as paleoherbs elose to the origin of monoeotyledon origin as well as key wood features that unite these families are cited.
Abstract: Stern and rhizome anatomy is reported for Anemopsis californica Hook., Houttuynia cordata Thunb., and Saururus cernuus L. Secondary growth is reported for the first time in Saururaceae. Cambia function indefinitely in Anemopsis in both fascicular and interfascicular areas. Interfascicular cambium is minimal in Saururus and absent in Houttuynia; fascicular cambium is present in both genera and produces a finite quantity of vessels, fiber-tracheids, and axial parenchyma but no rays. Anemopsis has vessels with simple perforation plates plus tracheids in wood, suggestive of adaptation to fluctuating water availability. The scalariform perforation plates of Houttuynia and Saururus suggest an unbroken history of occupancy of mesic habitats. Ethereal oil cells are reported for rays of Anemopsis, and for pith and cortex of the three genera studied. Stern idioblasts and other histologieal details are ineluded along with wood data in anatomical deseriptions of sterns. DNA data as weIl as maeromorphologie al data implicate Saururaeeae, along with Aristolochiaceae, Lactoridaceae, and Piperaceae as paleoherbs elose to the origin of monoeotyledons. Key wood features that unite these families are cited. Chloranthaeeae, whieh share stern endodermis and sealariform perforation plates with Saururaeeae, are also considered elose. Features of Saururaceae that are analyzed with respeet to monoeotyledon origin inelude loss of interfaseieular cambium, minimization of faseieular cambium, lack of imperforate traeheary elements in monocotyledon bundles, trimery, the sympodial habit, and production of adventitious roots.
TL;DR: The effectivity of early wound responses in A. mangium appears low as a second wound-associated process suberization of parenchyma cells contributes to the separation of wound-adjacent xylem tissue.
Abstract: Branches of 8-year-old trees of Acacia mangium Willd from a plantation in Malaysia were wounded After response periods from 1 to 4 weeks wound-adjacent xylem was investigated by electron microscopy Wounding induced the synthesis of dark-stained material in parenchyma cells with subsequent secretion through the pits into vessels and fibres After four weeks many of them contained wall-attached layers of this material Entirely filled vessels and fibres were not observed As a second wound-associated process suberization of parenchyma cells contributes to the separation of wound-adjacent xylem tissue Fungal degradation frequently occurred around the wound already three weeks after wounding The effectivity of early wound responses in A mangium appears low
TL;DR: There is an urgent need for more information on the effects of rainfall patterns and phenological periodicity on cambial activity and ring formation in the Dipterocarpaceae.
Abstract: The periodicity of leaf change and flowering and fruiting of tropical trees is discussed. Cambial activity patterns in tropical trees are reviewed. Emphasis is put on research undertaken in South-East Asia on the most important timber tree family in that region, the Dipterocarpaceae. There is an urgent need for more information on the effects of rainfall patterns and phenological periodicity on cambial activity and ring formation in this family
TL;DR: The wood anatomy of 24 species belonging to 18 genera of the Sapindaceae native to China is described and it is possible to key out individual genera as long as the unknown material is confined to Chinese species.
Abstract: The wood anatomy of 24 species belonging to 18 genera of the Sapindaceae native to China is described. Despite the wood anatomical homogeneity of the Chinese taxa of the family, it is possible to key out individual genera as long as the unknown material is confined to Chinese species. In general, the wood of Sapindaceae is characterised by diffuse-porous vessel distribution, simple perforations, alternate intervessei pits, comrnonly septate libriform fibres, usually scanty paratracheal parenchyma, mainly uniseriate rays and prismatic crystals common in chambered parenchyma and or fibres. The two taxa from temperate regions are ring-porous.
TL;DR: The maturation process of stegmata in the rattan palm Calamus axillaris Becc.
Abstract: The maturation process of stegmata in the rattan palm Calamus axillaris Becc. was investigated by electron microscopy. Near the apical meristem immature stegmata contain a dense cytoplasm and a centrally located nucleus, but no silica-bodies. Their cell walls, as weIl as those of adjacent fibres, show primary wall-like characteristics. At the third and fourth internode, silica-bodies form within a vacuole of the still immature stegmata; the nucleus becomes displaced towards the parenchyma side of a stegma. Between the fifth and tenth internode, the stegma walls thicken, first at the cell corners adjacent to fibres with subsequent extension to the fibre side. This part of a stegma wall becomes extremely thick and finally envelopes nearly half of the now fully developed silica-body. Its parenchyma side, however, remains free from additional wall material. After completion of wall thickening, the cytoplasm of a stegma degenerates.
TL;DR: The development of diffuse included phloem strands in Combretum nigricans sterns is described, which contrasts with previous descriptions and interpretations because these strands are not formed after redifferentiation of secondary xylem parenchyma.
Abstract: The development of diffuse included phloem strands in Combretum nigricans sterns is described, During a short period of time, a small phloem strand is cut off locally in an inward direction by an otherwise normal bidirectional vascular cambium. This contrasts with previous descriptions and interpretations because these strands are not formed after redifferentiation of secondary xylem parenchyma. A complementary cambium formed at the inner border of the young strand somewhat enlarges the strand and, during a relatively long period, produces secondary phloem outwards. Finally this complementary cambium stops functioning as a cambium and merges with the secondary phloem it has produced. Radial rows of cells are present within the included phloem strands which continue into the later-formed secondary xylem; rays transverse the strands. Crushing of the phloem takes place near the outer border of the strand, forming cap-like tissues of disorganized cells.
TL;DR: In this article, the wood of nine trees of Cecropia glazioui Sneth from three different areas of Serra do Mar in Sao Paulo was quantitatively analyzed and the modifications found in sampies of the most polluted region were in general in agreement with those present in woods from unfavourable environments, such as water-stressed sites.
Abstract: The wood of nine trees of Cecropia glazioui Sneth. from three different areas of Serra do Mar in Sao Paulo was quantitatively analysed. One of the areas is highly polluted by petrochemical, chemical, fertilizer and steel industries, another has hardly any pollution, and a third one was intermediate. The modifications found in sampies of the most polluted region were in general in agreement with those present in woods from unfavourable environments, such as water-stressed sites. Since the water is not a limiting factor in the area, pollution is believed to be responsible for the modified wood structure.
TL;DR: The wood anatomy of 31 species representing four genera of subtribe Myrciinae, Myrtaceae, Calyptranthes, Gomidesia, Marlierea and Myrcia is described and no anatomical features serve to separate the genera.
Abstract: The wood anatomy of 31 species representing four genera of subtribe Myrciinae, Myrtaceae, Calyptranthes, Gomidesia, Marlierea and Myrcia is described. In general the wood of subtribe Myrciinae can be characterised by solitary vessels, simple perforations, alternate vestured pits, fibres with bordered and/or vestured pits (fibre-tracheids), parenchyma scanty paratracheal, diffuse and/or diffuse-in-aggregates forming complete or interrupted bands, and heterocellular rays with disjunctive cell walls. The four genera share all these features, but exhibit considerable variation in axial parenchyma patterns and crystal occurrence and distribution. No anatomical features serve to separate the genera, but some, e.g., helical thickenings and crystals, appear to be restricted to species in one genus or another.
TL;DR: The wound response of a 35-year-old Royal palm has been investigated in order to understand the protective mechanisms and the origin of the staining.
Abstract: Mechanical damage of a palm stem endangers physiological functions, such as water transport, and induces quality reduction due to discolouration. The wound response of a 35-year-old Royal palm (Roystonea regia) has been investigated in order to understand the protective mechanisms and the origin of the staining. Wounds were induced in the basal and top regions 21, 14, 7 and 1 day(s) before the palm was felled. As initial reaction phenolic compounds are deposited in few of the smaller ground parenchyma cells. Subsequently slime fills up metaxylem vessels and protoxylem tracheids of both regions, whereas tyloses only develop in vessels at the top. Additionally, phenolic compounds originate also in phloem, vascular parenchyma, ground parenchyma and fibres.
TL;DR: Mature wood of extant Platanus kerrii Gagnep.
Abstract: Mature wood of extant Platanus kerrii Gagnep., native to Laos and Vietnam, is described for the first time. Its general characteristics are similar to other Platanus species; it has narrow, mostly solitary vessels, perforation plates both simple and scalariform, opposite intervessel pitting, diffuse-in-aggregates axial parenchyma, mostly wide (> 10-seriate) rays that usually are homocellular. Rays are wider (up to 30 cells wide) than in other extant species and in this feature P. kerrii resembles Cretaceous and Paleogene platanoid woods more than other extant species do. Vessel element lengths are similar to other species, although the incidence of scalariform perforation plates is greater than in other extant Platanus species.
TL;DR: Araucaria today is endemic to the Southern Hemisphere, with three species in Australia, but today only A. cunninghamii is cut commercially, mainly from plantations established in the last few decades.
Abstract: Araucaria today is endemic to the Southern Hemisphere, with three species in Australia. Araucaria cunninghamii Ait. ex D.Don (Hoop Pine) and A. bidwilli Hook. (Bunya Pine) were cut in the past and marketed together as Colonial Pine. Today only A. cunninghamii is cut commercially, mainly from plantations established in the last few decades.
TL;DR: It is suggested that the apoplastic continuum provided by parasite parenchyma provides for selective uptake of nutrients, whereas direct connections provide for bulk flow between host and parasite.
Abstract: The importance of direct tracheary element connections between mistletoes and their hosts is controversial Direct connections have been reported for four genera within the Viscaceae In the past such connections were considered essential for the movement of water and nutrients from host to parasite In contrast, recent authors have suggested that the apoplastic continuum provided by the walls of contiguous host and parasite parenchyma cells is the main pathway for the transfer of water and nutrients, with direct connections playing at best a minor role in uptake Our analysis of the parasite (Phoradendron)/host(Juglans) interface suggests otherwise Parenchyma predominates at the interface for both host (71%) and parasite (95%) While direct tracheary element connections are less frequent than other types of connections, they occurred in all sinkers analyzed Further, direct connections were much more abundant in host latewood (36%) than in earlywood (18%) This, and other evidence indicates that both pathways of transfer are important We suggest that the apoplastic continuum provided by parasite parenchyma provides for selective uptake of nutrients, whereas direct connections provide for bulk flow between host and parasite
Journal Article•
TL;DR: In this article, the residual direction of stress at the stem periphery in standing trees was measured with a sensor based on the single hole method, and the agreement between this macroscopic staining and characterization of tension wood on microtomed sections was checked.
Abstract: Populus euramericana cv 1214 is a clone of poplar widely planted in Europe. It is a fast growing species that produces white wood of low density appreciated in the veneer industry. However, it has defects : logs often split after felling, and veneers curve and twist after drying. The defects can be related to high levels of growth stresses and high heterogeneities of physical and mechanical properties, such as drying shrinkage and wood stiffness, due to tension wood. Our study aims at characterizing the properties of tension wood that seem to be the most important for explaining the afore-mentioned defects. Residual direction of stress at the stem periphery in standing trees was measured with a sensor based on the single hole method. Macroscopic distribution of tension wood has been studied in disks, stained with zinc iodo-chloride. The agreement between this macroscopic staining and characterization of tension wood on microtomed sections was checked. Logs (located under the disks) were peeled; drying shrinkages were measured in small veneers with an optical device, after a (measured) hygro-thermal recovery in order to release the greatest part of growth strains before drying. Tension wood seenis to he more frequently observed in leaning trees and in slender trees with small crowns. Tension wood is distributed in small patches grouped in generally one angular area. Longitudinal drying shrinkage is higher (about 0.5%) in tension wood than in normal (about 0.1%). Variations in tangential shrinkage seem not to be significant. The hygrothermal recovery has no significant influence on drying shrinkages. The residual maturation strains are higher in tension wood. The value of strains measured can be explained by the surface of G fibers located under the measurement, but the relation varies among trees. Both properties (maturation strains and drying shrinkages) are continuously distributed from 'sub-normal'wood with very small longitudinal maturation strain and drying shrinkage to very pronounced tension wood with high longitudinal maturation strain and drying shrinkage. Therefore, the usual classification into two categories 'normal'and 'tension' wood gives only poor information on wood properties and continuous quantitative data are preferable. (Resume d'auteur)
Journal Article•
TL;DR: Enhanced value of eucalypts from plantations for solid wood products remains limited by the appearance of end splits and warps when processing, and by the heterogeneity of their physical and mechanical properties, according to a study of variations of three properties.
Abstract: Enhanced value of eucalypts from plantations for solid wood products remains limited by the appearance of end splits and warps when processing, and by the heterogeneity of their physical and mechanical properties. We studied variations of three properties : specific gravity, longitudinal modulus of elasticity and growth strains. The study focused on plantations from Congo, China, Spain and France. According to our results, a cross section presents two types of variations : 1) the first, whose origin is morphogenetic, is a progressive transition of wood structure from the young state to the adult one. This transition induces variations of properties of the radius or according to the age of trees, particularly specific gravity; 2) the second is linked to the presence of tension wood, which induces sharp circumferential variations. This second heterogeneity occurs occasionally without any real relationship with the developmental stage of the tree, especially growth strains. Comparing plots of the same species, but with different ages, allowed determination of the existence of an age threshold beyond which growth strains are lower. Tendencies observed from the bottom to the top of the bole : 1) in the outer part of the stem, specific gravity and longitudinal modulus of elasticity both decrease, 2) near the pith, both properties are increasing. This could mean that, at a given cambial age, the wood from the upper part of the stem would be less 'juvenile' than the wood from the bottom. Comparisons, on a clone, of the level of growth strains from various spacings did not show significant differences. On the contrary, the setting (fertility class) and the genotype would have a marked influence on the level of growth strains. (Resume d'auteur)