Growth Ring Boundaries Research Articles

Salinity regulates radial growth of Cynometra ramiflora L. in the Sundarbans mangrove ecosystem

The mangrove biome is threatened by global environmental changes (including sea level rise, SLR) and anthropogenic disturbances. In this context, understanding the growth dynamics of mangrove species is essential for designing effective management plans for critical mangrove ecosystems such as the Bangladesh Sundarbans. Therefore, this study aims to (1) identify the growth-ring boundaries and tested their periodicity (annual nature) in one of the ecologically important understory mangrove species, Cynometra ramiflora in the Bangladesh Sundarbans, (2) determine the influences of climate and river discharge on radial growth, and (3) examine the influence of habitat variables (e.g., regulators, resources and forest structure) on radial growth. The growth-ring boundaries of C. ramiflora were distinct on the polished wood discs and marked by a layer of flattened fibers mixed with parenchyma. The agreement between individual growth-ring series and chronology statistics enabled us to develop for the first time a 42-year-long chronology spanning from 1979 to 2021. The results indicate that growth rings are annual and could be used for age and growth rate estimations. Monsoonal and annual precipitation enhanced radial growth. Growth was also positively influenced by the amount of river discharge received prior to the onset of growth, particularly during the pre-monsoon. Generalized additive models (GAMs) revealed that among the habitat variables, salinity had a strong negative influence on radial growth of the studied species in the Sundarbans, while tree density and diameter heterogeneity (coefficient of variation, CoV of diameter at breast height) had positive influences. This study revealed that C. ramiflora growth is strongly dependent on soil salinity and highlighted the potential of this approach for improving the prediction of future tree growth and distribution in the face of projected global changes, in particular, SLR.

Conifer fossil woods from the Upper Cretaceous (Neuquén Group) of Mendoza Province, Argentina

An assemblage of four silicified woods from the Neuquén Group (Upper Cretaceous) collected in the Cara Cura Mountain Range, southwest of Mendoza Province, Argentina is described. The specimens are composed of secondary xylem, and the preservation varies among them. Two specimens were assigned to Agathoxylon antarcticum (Poole et Cantrill) Pujana et al., related to Araucariaceae. This fossil-species is characterized by its distinct growth ring boundaries, uni- to biseriate araucarian pitting on tracheid radial walls, and araucarioid cross-fields. Other specimens could not be assigned to a fossil-genus because of their poor preservation, but they show a conifer anatomy. The distinct growth ring boundaries of some specimens suggest annual seasonality. Additionally, the presence of small globose structures in areas of highly degraded secondary xylem is consistent with the erosion bacteria type observed in modern and fossil woods.

Growth periodicity in semi-deciduous tropical tree species from the Congo Basin.

In the tropics, more precisely in equatorial dense rainforest, xylogenesis is driven by a little distinct climatological seasonality, and many tropical trees do not show clear growth rings. This makes retrospective analyses and modeling of future tree performance difficult. This research investigates the presence, the distinctness, and the periodicity of growth ring for dominant tree species in two semi-deciduous rainforests, which contrast in terms of precipitation dynamics. Eighteen tree species common to both forests were investigated. We used the cambial marking technique and then verified the presence and periodicity of growth-ring boundaries in the wood produced between pinning and collection by microscopic and macroscopic observation. The study showed that all eighteen species can form visible growth rings in both sites. However, the periodicity of ring formation varied significantly within and between species, and within sites. Trees from the site with clearly defined dry season had a higher likelihood to form periodical growth rings compared to those from the site where rainfall seasonality is less pronounced. The distinctness of the formed rings however did not show a site dependency. Periodical growth-ring formation was more likely in fast-growing trees. Furthermore, improvements can be made by a detailed study of the cambial activity through microcores taken at high temporal resolution, to get insight on the phenology of the lateral meristem.

Growth Rings in Nine Tree Species on a Neotropical Island with High Precipitation: Coco Island, Costa Rica

Coco Island, located 530 km off the Pacific coast of Costa Rica, experiences rainfall of over 7000 mm/year. This study aims to explore the distinctiveness of the growth ring boundaries and the dendrochronological potential (DP) of nine tree species found on Coco Island. The distinctiveness was classified into type 1: density variation; type 2: marginal parenchyma; type 3: fiber/parenchyma pattern; type 4: vessel distribution, and type 5: fiber band. Cecropia pittieri and Henriettella fascicularis lacked growth ring boundaries and, therefore, did not present any DP. Growth ring type 1 occurred in Ardisia compressa, Henriettea succosa, Henriettella odorata, and Psychotria cocosensis. Ocotea insularis and Sacoglottis holdridgei exhibited type 5 growth rings, with sufficient distinctiveness. Finally, Eugenia pacifica possessed growth rings of type 3 and type 4, but with limited distinctiveness in the growth ring boundary. In relation to DP, A. compressa, E. pacifica, and P. cocosensis presented low DP; meanwhile, H. succosa, H. odorata, O. insularis, and S. holdridgei demonstrated medium DP. If these species are found in abundance with a diameter exceeding 60 cm, a cross-dating technique like bomb-spike dating is established to confirm the annual growth of the ‘bands’. As these species exhibit some DP, they can be used to establish a chronology spanning 50–130 years, which could be utilized to create climate proxies or derive ecologically and climatically meaningful information. Additionally, the information presented could pave the way for future studies of sites that also have very high rainfall, where trees are presumed to lack annual growth rings.

Qualitative Anatomical Characteristics and Fiber Quality of Tapped Styrax sumatrana Wood Grown in North Sumatra, Indonesia

This study investigated the qualitative anatomical characteristics and fiber quality of tapped Styrax sumatrana wood to facilitate its further utilization. The transverse surface of the tapped S. sumatrana was light or greyish brown in the sapwood and reddish brown in the heartwood. The resin canals of the tapped wood were formed along the growth rings at the boundaries between the heartwood and sapwood. Furthermore, microscopic analyses revealed an irregular outline and rounded epithelial cells at the edges of the intercellular traumatic canal (TC). Approximately 8–16 epithelial cells surrounded the resin canals. The fibers in the tapped S. sumatrana were generally thin-walled, whereas those near the TC were thick-walled. Moreover, S. sumatrana were diffuse-porous and exhibited intermediately distinct or indistinct growth ring boundaries. The vessels were mainly radial multiples and clusters of 3–5. In addition, they showed a diagonal-to-radial pattern arrangement and a few tangential bands. Deposits were observed in some vessels in the tapped part but were absent in the untapped part. The fiber length of the tapped S. sumatrana wood was classified as moderate to extensive and categorized as second-grade pulp quality. Finally, the cell walls were classified as thin to moderate.

Angiosperm fossil woods from the Upper Cretaceous (Cardiel Formation) of Argentinean Patagonia

Abstract We describe nine angiosperm fossil woods from sediments of the Cardiel Formation (Upper Cretaceous) near the Cardiel Lake, Santa Cruz Province, Argentinian Patagonia. On the basis of the characteristics of the anatomy, the specimens were placed in three fossil species: Weinmannioxylon trichospermoides related to the Cunoniaceae, Burseroxylon panzai sp. nov. possibly related to the Anacardiaceae or Burseraceae, and a new taxon with unknown affinity, Tortorellixylon oligoporosum gen. et sp. nov. Angiosperms are 15% of the assemblage and conifers 85%, which is consistent with previous studies of fossil woods from the Late Cretaceous of Patagonia. Most specimens show poorly distinct growth ring boundaries that suggest a weakly marked annual seasonality during the deposition of the Cardiel Formation. In addition, the specimens’ size and the rings’ curvature are consistent with large trees. Decay patterns similar to those produced by modern xylophagous fungi are also recognized in most specimens. The identification of three species in an assemblage of nine fossil woods suggests a significant taxonomic richness of angiosperms, and the taxonomic composition suggests a Late Cretaceous age for the Cardiel Formation (probably Campanian–Maastrichtian). These new records allow a better understanding of the composition of the fossil forests of the Late Cretaceous of Patagonia, in which the tree canopy was apparently dominated by conifers.

Tree-ring dating of the common trees in Wadi Allaqi Biosphere Reserve, South-East Egypt

Twenty-five increment cores and tree discs were sampled for four common trees in Wadi Allaqi, an extremely arid region in South-East Egypt (19 for Acacia tortilis subsp. raddiana (Savi) Brenan and 2 for each of Balanites aegyptiaca (L.) Delile, Acacia ehrenbergiana Hayne, and Tamarix nilotica (Ehrenb.) Bunge). The main aim of the current study is to achieve a longer temporal perspective on growth, longevity, and marginal parenchyma of the wood samples. The growth ring boundaries of the acacias are differentiated by thin parenchyma bands, which run around the entire stem discs. Samples of Acacia tortilis subsp. raddiana were located along this Wadi from its upstream to downstream parts; based on the mean distance between the bands of marginal parenchyma, longevity, based on the marginal parenchyma bands, indicated that Acacia tortilis subsp. raddiana grew slowly and some of its studied individuals reflected 2 age scenarios in the downstream part, while the measurement interval reflected an established date of around 1884 or 1886. Both scenarios grew fast over a long period of time, and so the chiefly recent growth was dated back to 1885. Approximate dates for the midstream part dated back to 1648, while the overall growth for the upstream part dated back to 1482. Samples of Balanites aegyptiaca may be established between 1608 and 1715, while those of Acacia ehrenbergiana may be established between 1945 and 1975. Tamarix nilotica swiftly established itself, and a new ecosystem replaced the severe arid habitat after the dropping of the water level in 1980s.Two scenarios of age are probably true for the downstream part, implying a date of establishment between 1884 and 1886. It was also discovered that the outdated scenario for B. aegyptiaca and A. ehrenbergiana is more in line with asymptotic value and current growth, indicating larger possibility for future expansion.

Climate variability impacts on growth of African grape (Lannea microcarpa Engl & K. Krause) in West Africa

Lannea microcarpa is a deciduous tree with high socio-economic value in West African agroforestry systems. While climate-growth relationships remain unknown, this species is exposed to climate extremes. Knowledge of its response to climate variations is needed for its sustainable management. Therefore, the present study aimed to examine the growth of Lannea microcarpa in two climatic zones in West Africa (Sudanian zone of Mali and Sudano-Sahelian zone of Burkina Faso) using standard dendrochronological methods. In both sites, Lannea microcarpa forms distinct growth ring-boundaries characterized by a wider band with more parenchyma cell rows and is also marked by its solitary vessels. The two standard chronologies developed were significantly correlated with the precipitation records in both Burkina Faso (r2 = 0.41, n = 30 years, p < 0.01) and Mali (r2 =0.60, n = 53 years, p < 0.001). Furthermore, a strong relationship between major seasonal precipitation (between June and September) and residual chronology was observed in Burkina Faso (r2 = 0.51, n = 28 years, p < 0.01) and Mali (r2 = 0.65, n = 52 years, p < 0.001). The formation of annual growth rings is clearly influenced by climate variability, but not all variance is accounted for. The insignificant correlation between the chronologies of the two regions may be due to various factors, including differences in climate factors and soil conditions influencing buffered water availability. Similar studies on other tree species in West Africa will be useful.

ANATOMICAL INVESTIGATION OF FIVE GENERA THE LEAST-KNOWN TIMBER OF APOCYNACEAE AND THEIR POTENTIAL UTILIZATION

Doubtlessly, wood identification is critically important for a number of sectors, including government organizations, the wooden-based industry, museums, law enforcement, and scientists working in the fields of botany, ecology, forestry, and wood technology. Unfortunately, most wood species listed as “the least-known species” lack essential knowledge or even their anatomical feature and basic properties to promote their usage. This research aimed to investigate the anatomical characteristics and fiber quality of the least-known timber species of Apocynaceae family, which are authentic wood collection from Xylarium Bogoriense, namely , Ervatamia. sphaerocarpa, E. aurantiaca, Kopsia flavida, Lepiniopsis ternatensis, Plumeria acuminata, P. rubra, and Voacanga foetida. Wood samples have indistinct growth ring boundaries, diffuse-porous vessels in diagonal and/or radial pattern, vessels in radial multiples of 4 or more cells, simple perforation plate, alternate intervessel pits; distinct borders of vessel-ray pits, similar with those of intervessel pits in size and shape throughout the ray cell, and septate fibers with simple pits to minutely bordered pits which are common in radial and tangential walls. Based on the fiber length and the derived values of fiber dimension, some species are classified into Quality Class II and III, and the rest of them are classified into Quality Class II or III for pulp and paper manufacturing. Based on general characteristics, commonly Apocynaceae can be used as handicrafts raw material. Based on the fiber quality, some species which are classified into Quality Class II, are predicted to have potential as pulp and paper material with medium quality.

Multiscale wood micromechanics and size effects study via nanoindentation

Wood as a material is a natural composite with a complex hierarchically arranged structure. All scale levels of wood structure contribute to its macroscopic mechanical properties. The nature of such characteristics and deformation modes differs radically at different scale levels. Wood macroscopic properties are well studied, and the relevant information can be easily found in the literature. However, the knowledge of the deformation mechanisms at the mesoscopic level corresponding to the cellular structure of early and late wood layers of annual growth rings is insufficient. It hinders building the comprehensive multiscale model of how wood mechanical properties are formed. This paper described the results of scanning of mechanical properties of softwood and hardwood samples, such as common pine, small-leaf lime, and pedunculate oak, by means of nanoindentation (NI). The NI technique allows varying the size of deformed region within a wide range by altering maximal load (Pmax) applied to the indenter so that one can repeatedly and non-destructively test wood structural components at different scale levels on the same sample without changing the technique or equipment. It was discovered that the effective microhardness (Heff) and Young's modulus (Eeff) decreased manifold with Pmax growing from 0.2 to 2 000 mN. This drop in Heff was observed when the locally deformed region grew, and resulting from Pmax increase generally follows the rule similar to the Hall-Petch relation for yield stress, strength, and hardness initially established for metals and alloys, though obviously in those cases the underlying internal mechanisms are quite different. The nature and micromechanisms of such size effect (SE) in wood revealed using NI were discussed in this study. At Pmax < 0.2 mN, the deformed area under the pyramidal Berckovich indenter was much smaller than the cell wall width. Hence, in this case, NI measured the internal mechanical properties of the cell wall material as long as free boundaries impact could be neglected. At Pmax > 200 mN, the indentation encompassed several cells. The measured mechanical properties were significantly affected by bending deformation and buckling collapse of cell walls, reducing Heff and Eeff substantially. At Pmax ≈ 1–100 mN, an indenter interacted with different elements of the cell structure and capillary network, resulting in intermediate values of Heff and Eeff. Abrupt changes in Heff and Eeff at annual growth ring boundaries allow accurate measuring of rings width, while smoother and less pronounced changes within the rings allow identification of earlywood and latewood layers as well as any finer changes during vegetation season. The values of ring width measured using NI and standard optical method coincide with 2%−3% accuracy. The approaches and results presented in this study could improve the understanding of nature and mechanisms lying behind the micromechanical properties of wood, help to optimize the technologies of wood farming, subsequent reinforcement, and utilization, as well as to develop new highly informative techniques in dendrochronology and dendroclimatology.

The adjustment of China endemic Heptacodium miconioides Rehd. to temperate zone of Poland

Heptacodium miconioides is an increasingly popular ornamental plant, originally being endemic to China. The late and long flowering determines its ecological and ornamental value in cultivation. The aims of this research were to define and distinguish phenological phases of the development of Heptacodium miconioides in the temperate zone region and identification of anatomical changes within the stem during autumn in relation to phenological phases and climatic conditions. Phenological observations were carried out in Wrocław during 2012–2013, as well as in Warsaw (Poland, 52.6°N, 20.5°E) during 2018–2021. During the last year of research an analysis of the anatomical structure was carried out for young stems that bore flowers that year, as well as older, 2- to 6-year-old ones. The material was collected H1 – 10.09., H2 – 28.09., H3 – 16.10., H4 – 3.11., H5 – 21.11. The width of annual increments in subsequent years was determined; length, width and vessel density in early and latewood for subsequent rings of annual growth was measured, as well as the width of the phloem in 1–6-year-old stems (2016–2021). In the vegetative stage three main stages of development were distinguished (leaf buds have the green tips; full autumn discoloration of leaves; leaves falling). In the generative phase, which lasted on average from August 22nd to January the 7th five main phases of development were distinguished (flowering, unripe fruits, ripe fruits, spreading of seeds). Increased average temperature during winter and spring had an effect on the growth pattern: early phenological stages occurred sooner and foliage development lasted 44 days longer. Flowering occurred at a similar date at both observed locations and climatic conditions. This year’s shoots flowering on a radial section with axial symmetry, were slightly flattened and in clusters arranged regularly to match the shape. Heptacodium develops 2–6 years old shoots with radial symmetry. The growth ring boundaries are distinct, the wood semi-rings porous, with marked differences in the structure of the primary and secondary shoot. Lignification of tissues before winter ends during late leaf-fall phase. The research indicated the adaptive potential of Heptacodium in response to climatic conditions of temperate zone.

Largest fossil logs of Paraphyllanthoxylon-type from the Eastern Hemisphere (Upper Cretaceous, Czech Republic)

The fossil genus Paraphyllanthoxylon is known from many localities around the world. In some cases, the fossilized logs can reach quite large proportions. We present the findings of large fossil logs (the two biggest logs have diameter 98 cm, length minimally 11 m, estimated height 34 m, and diameter 93 cm, length 7 m, estimated height 32.5 m) with Paraphyllanthoxylon type of wood from the Klikov Formation (Turonian–Santonian) in South Bohemia (Czech Republic). These are the largest documented logs from the Eastern Hemisphere from Upper Cretaceous. Our study clarifies for the first time the geological context of fossil wood finds from the South Bohemian Basins. The fossiliferous strata represent a bedload sedimentation in a series of low-sinuosity, braided stream channels. The palaeovegetation reconstruction indicates that trees of Paraphyllanthoxylon-type apparently dominated at the locality, but platanoids and plants of Normapolles complex were also present. No distinct growth ring boundaries were seen, but there were variations in vessel frequency. These changes in wood anatomy were unique and probably associated with rare events in the ecosystem, perhaps a major flood.

Qualitative anatomical characteristics of the virgin cork in Quercus variabilis grown in Korea

To provide information on the identification and quality evaluation of Q. variabilis virgin cork from Korea, the qualitative anatomical characteristics of the virgin cork were observed by optical and scanning electron microscopy and compared with those of Q. suber reproduction cork from Portugal. Q. variabilis showed a narrower growth ring than Q. suber. A dark-brown zone with sclereids was found only in Q. variabilis cork. The lenticular channel in Q. variabilis is larger than that in Q. suber. Q. variabilis virgin cork showed a distinct growth ring boundary and an abrupt transition from earlycork to latecork with a few rows of latecork cells. Q. suber reproduction cork showed an indistinct growth ring with a gradual transition from one to two rows of latecork cells. In the earlycork, Q. suber showed mild corrugation, while Q. variabilis displayed significant corrugation with collapsed and distorted cork cells. The lenticular channel in Q. variabilis virgin cork was surrounded by thick-walled cells filled with compact lenticular filling tissue. Q. suber reproduction cork had an opening with loose lenticular filling tissue surrounded by thick-walled cells. Prismatic crystals, thick-walled sclereid cells, and fiber-sclereids were found only in Q. variabilis. A few trabeculae were found in both cork samples.

Understanding the effect of PF glue impregnation on the shear strength of wood growth ring boundary

Understanding the effect of PF glue impregnation on the shear strength of wood growth ring boundary

Climate-growth relationships of Daniellia oliveri (Rolfe) Hutch. & Dalziel in the Sudanian zone of Mali, West Africa

Tree rings depend on seasonal variation in radial tree growth. Where they can be identified, their interannual variation may reflect climate variability. Compared to its use in temperate and boreal regions, tree-ring analysis has been less applied in tropical Africa, with weaker seasonality. Daniellia oliveri often forms the tallest trees in agroforestry parklands of the Sudanian savanna zone of Mali but its growth response to climate (rainfall, temperature) variability has not been documented. We analyzed six stem disks of D. oliveri and used standard dendrochronological methods to process the samples. Contrary to earlier literature likely based on more humid parts of the species distribution range, D. oliveri formed distinct growth ring boundaries in our study area. The mean annual radial growth was 2.73 ± 0.56 mm. All measured tree-ring series were successfully cross-dated with a GLK (Gleichläufigkeit) value of 76.3 ± 5.6. The final tree-ring chronology covers the period 1909-2021. After removing age-related growth trends, the tree-ring width index showed a significant relationship with records of annual rainfall (r2 = 0.46, n = 100 years, p < 0.001). The relationship between wet-season (June to September) precipitation and the residual chronology was slightly higher (r2 = 0.50, n = 100 years, p < 0.001). However, no significant correlation was found for temperature. These results imply that D. oliveri can be successfully used for dendrochronological studies with relevance for the management and restoration of the ecosystems in the Sudanian zone of West Africa, where long-term rainfall records are scarce.

High-precision 14C measurements of parenchyma-rich Hymenolobium petraeum tree species confirm bomb-peak atmospheric levels and reveal local fossil-fuel CO2 emissions in the Central Amazon

Atmospheric radiocarbon (14C) recorded in tree rings has been widely used for atmospheric 14C calibration purposes and climate studies. But atmospheric 14C records have been limited along tropical latitudes. Here we report a sequence from 1938 to 2007 of precisely measured 14C dates in tree rings of the parenchyma-rich Hymenolobium petraeum tree species (Porto Trombetas, 1°S, 56°W) from the Central Brazilian Amazon. H. petraeum has discernible growth ring boundaries that allow dating techniques to be employed to produce calendrical dates. Bomb-peak tree-ring 14C reconstruction coincides with the broader changes associated with reported values of the Southern Hemisphere atmospheric 14C curve (SH zone 3; values within the ±2σ interval), suggesting that inter-hemispheric air-mass transport of excess-14C injected into the stratosphere during intensive atmospheric nuclear tests is relatively uniform across distinct longitudinal regions. From the early 1980s onwards, H. petraeum had lower 14C values than other pantropical 14C records. Through 14C-based estimation, we found a strong influence of fossil-fuel CO2 contributions from Porto Trombetas mining operations and shipping traffic on inland waterways. An increase of at least 6.3 ± 0.8 ppm of fossil-fuel CO2 has been detected by 14C. Our findings invite further 14C analyses using tree rings of tropical tree species as a potential tracer for a wide range of environmental sources of atmospheric 14C-variability.

A MICRO-GRAPH RETRIEVAL SYSTEM FOR CONIFEROUS WOODS USING MULTIPLE METHODS

Inspired by the successful application of deep convolutional neural network, a coniferous micro-graphs retrieval framework based on deep learning and image processing technology is proposed. The idea of the proposed framework is that the texture feature of representing three section surfaces can be learned and classified by a fully CNN, and the canals can be deep learned by an U-net CNN when the data labels are available. In addition, the image processing technologies are also proposed to identify whether the growth ring boundaries are distinct and whether there is a “window-like” cross-field pitting. Finally, a coniferous micro-graphs retrieval system is realized based the proposed methods. Experimental results demonstrate that this system outperforms in terms of recognition accuracy. In addition, the system can be further developed into more intelligent coniferous retrieval system that can automatically identify more coniferous microscopic features, so as to obtain more accurate retrieval results.

Assessment of the differences between juvenile and mature woods of Populus alba trees in the longitudinal and radial axes of the stem

The aim of this study was to evaluate the differences between juvenile and mature woods of Populus alba trees in the axial and radial directions of the stem. For this purpose, three stands of P. alba trees were randomly chosen and cut from at their diameter at breast height. Three disks with a thickness of 5 cm were taken at three different height levels along the tree stems. The specimens were sequentially cut in the radial position according to the ISO standards method. The results indicated that there are significant differences in the physical and biometric features of P. alba trees in the longitudinal and radial axes of the stem. As the height from the base of the tree to the top of the stem increased, the oven-dry density, basic density, and fiber biometric factors decreased. Moreover, as the distance from the pith to the bark increased, the oven-dry density, basic density, and fiber biometric factors increased. The microscopic study represented that the P. alba is a semi-ring-porous hardwood with distinct growth ring boundaries, simple perforation, homogenous rays, and alternative inter-vessel pits.

Brachyoxylon fossil woods with traumatic resin canals from the Upper Cretaceous Cerro Fortaleza Formation, southern Patagonia (Santa Cruz Province, Argentina)

Two silicified fossil woods from outcrops of the Cerro Fortaleza Formation (Campanian, Upper Cretaceous) in Los Hornos Hill, Santa Cruz Province, Argentina are described. Based on their anatomical characteristics, both specimens were assigned to a new species of the fossil genus Brachyoxylon Hollick and Jeffrey, B. patagonicum sp. nov. They are characterized by having distinct growth ring boundaries, absence of axial parenchyma, uniseriate rays, mixed and uniseriate intertracheary radial pitting, and araucarioid cross-fields with 1–8 circular half-bordered pits per cross-field. In turn, one specimen has three rows of axial traumatic resin canals parallel to the growth rings were identified close to the middle of the growth rings or close to the latewood. Approximately 45% of Brachyoxylon species present traumatic resin canals, which suggests that they are a common feature of this fossil genus. Alternatively, the specimen with the canals shows biological remains (hyphae) and wood fungal degradation patterns, which may be thought as some of those of possible organisms contributing to the formation of the resin canals. This record provides fresh evidence attesting to the abundance and widespread distribution of Cheirolepidiaceae in the Cretaceous of Patagonia.

Growth-ring boundaries of tropical tree species: Aiding delimitation by long histological sections and wood density profiles

Recent methodological advances have opened new perspectives for tropical dendrochonological studies by facilitating the visualization, delimitation, and analyses of tree-rings. One of those improvements was brought by X-ray densitometry, which allows building radial wood density profiles at microscopic scale. Furthermore, recent methods allow for cutting long histological sections to study anatomical variations along the entire radius of trees. These techniques have mainly been applied to low wood-density species from temperate and Mediterranean regions, with only limited applications in the tropics. Here we provide an improved protocol that allows for obtaining long histological sections of tropical woods, apply it to six species with varying wood densities 0.45−0.85 g cm−3 (Eucalyptus grandis, Tectona grandis, Acacia mangium, Cedrela fissilis, Hymenaea courbaril, and Copaifera duckei), and explore potential applications for tree-ring analyses. We provide instructions on core-microtome knife adjustments, procedures for softening and sectioning long histological samples of high wood-density species. We also present a multi-proxy approach that combines X-ray density profiles with the histological sections that improve the characterization and distinction of the various and complex tropical growth rings anatomical markers (fibre zone, marginal parenchyma, and ring porosity). This multi-proxy approach also opens the door for obtaining quantitative anatomy and physical parameters of tropical species with (intra-annual resolution. Our proposed approach is thus not only an additional tool to improve ring-boundary delimitation of tropical species, but it also paves the way to more innovative, borderline approaches in tropical dendrochronology.