Sources of phenotypic variation of wood density and relationships with mean growth in two Eucalyptus species in Argentina

Aims of the study: To describe the radial patterns of wood density, and to identify their main sources of variation, and the potential tradeoffs with mean tree growth, in two Eucalyptus species. Area of study: Mesopotamian (Corrientes and Entre Ríos provinces) and Pampean region (Buenos Aires province) of Argentina. Materials and methods: Eucalyptus grandis and Eucalyptus viminalis, growing in genetic trials installed in two sites per species were studied. X-ray wood microdensity profiles were developed from core samples. Each profile was proportionally divided in 10 sections. Mean, maximum, minimum and the standard deviation of wood density, for each section were computed. Mean annual growth was used to study the relationships with wood microdensity variables. A linear mixed-effects model computed the significance of different sources of phenotypic variation. Pearson´s correlation computed the relationships between variables. Main results: The pattern of radial variation in E. grandis showed a decrease in wood density from pith to bark, mainly due to the decrease in minimum wood density, while in E. viminalis, wood density increased towards the outer wood. In both species, the standard deviation of the wood density increased along the radial profile from pith to bark. Significant variation in wood density was explained by site, provenance and clone/family effects. In E. grandis mean, maximum and minimum wood density were negatively correlated with mean growth, whereas in E. viminalis correlations were positive but close to zero. Research highlights: Both the pattern of radial variation of wood density and the relationship between wood density and mean growth were different in the studied Eucalyptus species, and they varied within species depending on the site they were growing and genetic provenance.

Anatomical characterization of Chimonobambusa quadrangularis based on circumferential and radial variation patterns in cross-sections

The anatomical structure of the bamboo stem is characterized by vascular bundles comprising the xylem, phloem, and sclerenchyma fibrous sheaths as well as parenchymatous ground tissue in which the vascular bundles are embedded. The composition of the stem is the main factor influencing the anatomical characteristics of circular bamboo, which shows considerable variation in the radial direction. However, most species of Chimonobambusa have square stems. Here, we tested the hypothesis that circumferential variation exists in the cross-sectional anatomy of this species. We analysed fibre morphology and the cross-sectional structural characteristics of vascular bundles of Chimonobambusa quadrangularis (Fenzi) Makino and their associated circumferential and radial variation in cross-sections. Microscopic observations were conducted to identify, measure, and compare fibre morphology and the structural characteristics of vascular bundles, including both circumferential and radial anatomical variation. Vascular bundles occurred as undifferentiated, semi-differentiated, and open types in the radial direction with no changes in the circumferential direction. The average length, width, and ratio of fibre length to width were 1463.6 μm, 12.3 μm and 119.3 in the corner region, and 1452.7 μm, 12.8 μm, and 111.3 in the side region, and there were significant circumferential and radial differences in length, width, and the ratio of fibre length to width (). The circumferential variation in density of vascular bundles, the ratio of fibre length to width, radial to tangential diameter ratio of vascular bundles, and the proportion of sclerenchyma were greater in the corner regions than the side regions. The variation in fibre width and the proportion of parenchyma were greater in the corner regions than in the side regions. The density of vascular bundles and proportions of sclerenchyma were greater in the outer stem compared to the inner stem, whereas the length, width, and ratio of fibre length to width were greatest in the centre compared to the inner and outer zones. Circumferential variation of the density of vascular bundles, fibre length and fibre width occurred in the central and outer stem zones. These findings confirm that there are significant anatomical variations in both the circumferential and radial directions and provide a scientific basis for the rational use of Chimonobambusa quadrangularis.

Radial variation studies on wood properties of Populus deltoides parents and their hybrids

The radial variation and the genetic variation of wood properties between the parents and offspring of Populus deltoides were studied in this work. The chemical composition, density, and anatomical characteristics of Populus deltoides cl. ‘Danhong’ and its offspring exhibited the phenomenon of transgressive segregation. The chemical compositions of the parents and offspring were decreased in several attributes (benzene alcohol extract, hemicelluloses, lignin) with the increase of the cambial age. Moreover, the fibre length, fibre width, ratio of fibre length to width, and wall thickness to lumen ratio of parents and offspring were increased with cambial age. In addition, the densities of parents and offspring were increased with the increase of cambial age. There were significant differences in wood properties among Populus deltoides and its hybrids. These results indicated that Populus deltoides cl. ‘Danhong’ could be considered as pulp material and Populus deltoides cl. ‘Nanyang’ as building material. According to the radial variation rule of each material character, the rotation cutting period can be selected as years 7 or 8.

Radial Variation of Wood Anatomical Properties Determines the Demarcation of Juvenile-Mature Wood in Schima superba

Schima superba is a precious broadleaf tree species that produces excellent timber. Analyzing the radial variation of wood anatomical properties within stems and determining the boundary between the juvenile and mature wood can provide a theoretical basis for the breeding and cultivation of S. superba. Herein, 30 54-year-old trees were used to analyze the radial variation of wood anatomical properties qualitatively. The correlation among wood properties was analyzed. On this basis, four types of model were used to predict the wood properties quantitatively, and the optimal segmentation model was used to determine the boundary between juvenile and mature wood. The results showed that the variation of the early stage (before the 20th year) was larger than that of the later stage (after the 20th year); moreover, the variation of the vessel features (9.56%) was greater than that of the fiber features (7.42%), the vessel lumen diameter (11.94%) and the fiber length (8.00%) had the most variation. There were three radial variation patterns in the wood properties. In the early stage, there was a significant positive correlation between the ring width and wood air-dry density (0.78) and wood basic density (0.89), and a significant negative correlation between the ring width and the fiber characters (−0.79~−0.93) and vessel characters (−0.64~−0.90). The growth models of Logistic and Richards were more suitable (R2 = 84.2%~95.2%) for the radial variation of wood anatomical properties than the nonlinear least square model (R2 = 67.7%~90.9%). The transition wood between juvenile and mature wood of S. superba was from the 11th to the 16th year based on aggregative indicators from the pith to bark at breast height. Finally, when taken together, the wood anatomical properties of S. superba had regular radial variation. Breeding programs need to consider both growth and wood anatomical properties in the early stage, but they can be neglected in the mature stage. The formation of mature wood of S. superba occurred after the 16th year.

Radial variation of the stellar mass functions in the globular clusters M15 and M30: clues of a non-standard IMF?

ABSTRACT We exploit a combination of high-resolution Hubble Space Telescope and wide-field ESO-VLT observations to study the slope of the global mass function (αG) and its radial variation (α(r)) in the two dense, massive and post core-collapse globular clusters M15 and M30. The available data set samples the clusters’ main sequence down to ∼0.2 M⊙ and the photometric completeness allows the study of the mass function between 0.40 M⊙ and 0.75 M⊙ from the central regions out to their tidal radii. We find that both clusters show a very similar variation in α(r) as a function of clustercentric distance. They both exhibit a very steep variation in α(r) in the central regions, which then attains almost constant values in the outskirts. Such a behaviour can be interpreted as the result of long-term dynamical evolution of the systems driven by mass-segregation and mass-loss processes. We compare these results with a set of direct N-body simulations and find that they are only able to reproduce the observed values of α(r) and αG at dynamical ages (t/trh) significantly larger than those derived from the observed properties of both clusters. We investigate possible physical mechanisms responsible for such a discrepancy and argue that both clusters might be born with a non-standard (flatter/bottom-lighter) initial mass function.

Radial variation in tracheid lengths in dominant trees of selected coniferous species

The radial variation was examined for tracheid lengths of Norway spruce (Picea abies (L.) Karst.), European larch (Larix decidua Mill.), and Scots pine (Pinus sylvestris L.) wood from dominant trees coming from an even-aged stand, and growing under identical forest site and climatic conditions. The measurements were completed on macerated material. The variation of tracheid lengths in annual rings from the core to the bark was used for determination of the border between the juvenile and mature wood in the trunk cross-section. The boundary age between the juvenile and mature wood zones established for the examined species was comparable, as it was 25 annual rings for Scots pine and 29 for European larch and for Norway spruce. In the juvenile zone, the tracheid lengths increased 2.2-fold in Norway spruce wood, while in Scots pine and European larch wood it was approximately 1.7-fold. By contrast, in the mature wood zone the tracheid lengths was stabilized at a certain level, showing slight fluctuations. The differences in the tracheids length of early and late wood in the examined annual rings were also determined, and it was established that for the majority of annual rings they are statistically significant (p<0.05).