Browse results

You are looking at 91 - 100 of 1,941 items for :

  • All content x
  • Chapters/Articles x
Clear All

Neda Lotfiomran and Michael Köhl

Reliable information on tree growth is a prerequisite for sustainable forest management (SFM). However, in tropical forests its implementation is often hampered by insufficient knowledge of the growth dynamics of trees. Although tree ring analysis of tropical trees has a long history, its application for SFM has only recently been considered. In the current study, we illustrate both the potentials and limitations of a retrospective growth assessment by tree ring analysis under the prevailing tropical conditions in a Surinamese rain forest. For this purpose, 38 commercial tree species were screened and grouped into three categories according to the visibility of their tree ring boundaries: (I) tree rings absent or indistinct, (II) distinct but partially vague tree rings which enable approximate age estimation, (III) very distinct tree rings. In 22 out of 38 commercial tree species distinct to very distinct tree ring boundaries could be identified. The anatomy of tree ring boundaries was described following Worbes and Fichtler (2010). Four species with distinct growth rings, Cedrela odorata, Hymenaea courbaril, Pithecellobium corymbosum and Goupia glabra, were studied in greater detail. Time-series analysis was used to characterise their radial growth. From the tree ring width, the annual diameter increment and cumulative diameter growth were calculated to find long-term growth patterns. Pithecellobium corymbosum and partially Hymenaea courbaril followed a typical S-shaped growth curve. By contrast, Goupia glabra and Cedrela odorata did not exhibit an age-related decrease of growth, but showed a constant linear growth over their entire life span. If based on more sample trees, such data can provide target-oriented information for improving SFM in tropical forests.

Caian Souza Gerolamo and Veronica Angyalossy

This work compares potential xylem hydraulic efficiency among Bignoniaceae lianas, shrubs and trees. Five species from each growth habit were analysed to determine variance among habits based on quantitative and qualitative wood anatomical features. Potential hydraulic conductivity was calculated for each species in order to compare efficiency of water transport. Cambial variants are present in the Bignonieae tribe, as phloem wedges in lianas and phloem arcs in shrubs. Lianas present vessel dimorphism, quantitatively evidenced by the ratio of maximum by minimum vessel diameter of about 20, higher percentage of vessel area and lower percentage of fibres compared with the self-supporting species studied here. Potential hydraulic conductivity is higher in lianas due to the presence of wider vessels and it is hypothesised that the narrow vessels can function as back-up for water conduction when wider vessels are cavitated.

Nathan A. Jud, Elisabeth A. Wheeler, Gar W. Rothwell and Ruth A. Stockey

Fossil angiosperm wood was collected from shallow marine deposits in the Upper Cretaceous (Coniacian) Comox Formation on Vancouver Island, British Columbia, Canada. The largest specimen is a log at least 2 m long and 38 cm in diameter. Thin sections from a sample of this log reveal diffuseporous wood with indistinct growth rings and anatomy similar to Paraphyllanthoxylon. Occasional idioblasts with dark contents in the rays distinguish this wood from previously known Paraphyllanthoxylon species and suggest affinity with Lauraceae. The log also includes galleries filled with dry-wood termite coprolites. This trunk reveals the presence of tree-sized angiosperms in what is now British Columbia, and the association of dry-wood termites with angiosperm woods by the Coniacian (89 Ma). To understand the significance of this discovery, we reviewed the record of Cretaceous woods from North America. Our analysis of the distribution of fossil wood occurrences from Cretaceous deposits supports the conclusion that there was a strong latitudinal gradient in both the size and distribution of angiosperm trees during the Late Cretaceous, with no reports of Cretaceous angiosperm trees north of 50°N paleo-latitude in North America. The rarity of angiosperm wood in the Cretaceous has long been used to support the idea that flowering plants were generally of low-stature for much of the Cretaceous; however, large-stature trees with Paraphyllanthoxylon-like wood anatomy were widespread at lower–middle paleo-latitudes at least in North America during the Late Cretaceous. Thus, the presence of a large Paraphyllanthoxylon log in the Comox Formation suggests that Vancouver Island has moved significantly northward since the Coniacian as indicated by other geological and paleobotanical studies.

Jimmy Thomas and David A. Collings

We describe a novel, semi-automatic method for the detection, visualisation and quantification of axially oriented resin canals in transverse sections of Pinus radiata D. Don (radiata pine) trees. Sections were imaged with a flatbed scanner using circularly polarised transmitted light, with the resin canals that contained only primary cell walls appearing dark against a bright background of highly-birefringent tracheids. These images were analysed using ImageJ software and allowed for a non-biased, automated detection of resin canals and their spatial distribution across the entire stem. We analysed 8-month-old trees that had been subjected to tilting to induce compression wood and rocking to simulate the effects of wind. These experiments showed that both rocking and tilting promoted the formation of wood and confirmed that resin canals were most common adjacent to the pith. Both the rocking and tilting treatments caused a decrease in the number of resin canals per unit area when compared to vertical controls, but this change was due to the increased formation of wood by these treatments. In tilted samples, however, analysis of resin canal distribution showed that canals were more common on the lower sides of stems but these canals were excluded from regions that formed compression wood.

Barbara Ghislain and Bruno Clair

Tension wood, a tissue developed by angiosperm trees to actively recover their verticality, has long been defined by the presence of an unlignified cellulosic inner layer in the cell wall of fibres, called the G-layer. Although it was known that some species have no G-layer, the definition was appropriate since it enabled easy detection of tension wood zones using various staining techniques for either cellulose or lignin. For several years now, irrespective of its anatomical structure, tension wood has been defined by its high mechanical internal tensile stress. This definition enables screening of the diversity of cell walls in tension wood fibres. Recent results obtained in tropical species with tension wood with a delay in the lignification of the G-layer opened our eyes to the effective presence of large amounts of lignin in the G-layer of some species. This led us to review older literature mentioning the presence of lignin deposits in the G-layer and give them credit. Advances in the knowledge of tension wood fibres allow us to reconsider some previous classifications of the diversity in the organisation of the fibre walls of the tension wood.

Philip D. Evans, Ignacio A. Mundo, Michael C. Wiemann, Gabriela D. Chavarria, Pamela J. McClure, Doina Voin and Edgard O. Espinoza

Determining the species source of logs and planks suspected of being Araucaria araucana (Molina) K.Koch (CITES Appendix I) using traditional wood anatomy has been difficult, because its anatomical features are not diagnostic. Additionally, anatomical studies of Araucaria angustifolia (Bertol.) Kuntze, Araucaria heterophylla (Salisb.) Franco, Agathis australis (D.Don) Lindl., and Wollemia nobilis W.G.Jones, K.D.Hill & J.M.Allen have reported that these taxa have similar and indistinguishable anatomical characters from A. araucana. Transnational shipments of illegal timber obscure their geographic provenance, and therefore identification using wood anatomy alone is insufficient in a criminal proceeding. In this study we examine the macroscopic appearance of selected members of the Araucariaceae and investigate whether analysis of heartwood chemotypes using Direct Analysis in Real Time (DART) Time-of-Flight Mass Spectrometry (TOFMS) is useful for making species determinations. DART TOFMS data were collected from 5 species (n =75 spectra). The spectra were analyzsed statistically using supervised and unsupervised classification algorithms. Results indicate that A. araucana can be distinguished from the look-alike taxa. Another statistical inference of the data suggests that Wollemia nobilis is more similar and within the same clade as Agathis australis. We conclude that DART TOFMS spectra can help in making species determination of the Araucariaceae even when the geographic provenance is unknown.

R.C. Mehrotra and Gaurav Srivastava

Fossil wood was collected from an in situ upright tree encased in the late Oligocene mudstone sediments exposed in the Tirap Mine, Makum Coalfield, Tinsukia district, Assam. The wood belongs to Careya of the Lecythidaceae. This genus is reported for the first time from Paleogene sediments. Its presence supports the occurrence of tropical evergreen to deciduous forests in the region during the depositional period.

Chieuda Nguyen, Ashley Andrews, Pieter Baas, Jason E. Bond, Maria Auad and Roland Dute

Chionanthus retusus and most Osmanthus spp. possess torus-bearing intervascular pit membranes in their woods. Because the genera involved are thought to be closely related and are members of the subtribe Oleinae, we hypothesized that torus morphology should be similar across taxa. A study combining light, scanning electron, and atomic force microscopy indicates that tori in both genera comprise a bipartite thickening containing a central pustular region and an encircling corona. Removal of incrusting material from the torus exposes subtending sets of parallel microfibrils. We hypothesize that the torus structures of C. retusus and Osmanthus spp. (as represented by O. armatus) have the same morphology. Optimizing torus-bearing pits on published molecular phylogenies of the subtribe Oleinae indicates parallel evolution as an explanation for torus similarity between these two groups, although a robust and well-resolved phylogeny of the Oleaceae is still lacking. A brief study of the wood anatomy of Olea dioica was also undertaken. This species is a member of the subgenus Tetrapilus and thought to be closely related to torus-bearing genera of the Oleaceae. Despite the close relationship, no tori were observed in O. dioica.

Roberto R. Pujana and Daniela P. Ruiz

A new species of Podocarpoxylon Gothan is described based on samples collected from sediments of the Río Turbio Formation. The fossil-bearing strata are lower Eocene (47–46 Mya) according to recent geochronological ages. The new species has indistinct growth ring boundaries, abundant and frequently tangentially zonate axial parenchyma, uniseriate pitting on radial walls, one half-bordered pit (= oculipore) with reduced borders and vertical aperture inclination per cross-field and medium height uniseriate rays. The new material is compared with all fossil-species of Podocarpoxylon and an inventory of all Podocarpoxylon species previously described is provided. Cross-field characters of the new species indicate affinity to the Podocarpaceae. The presence of Podocarpaceae wood augments other evidence of this family from the same stratigraphic unit.

Peter Gasson and Pieter Baas