Anatomical Atlas of the Quail's Ear (Coturnix coturnix)

This study aims to enhance the anatomical knowledge of the ear of the adult quail (Coturnix coturnix) through the creation of a scaled 3D model utilizing data from micro‐CT images. In addition, 17 annotated histological sections of the quail's ear are aligned to their 3D position in the model. The resulting anatomical atlas provides an intuitive insight into the 3D anatomy and can be used for medical education. The model also allows measuring anatomical structures and can thus serve as reference for the quail's auricular anatomy and as a basis to evaluate clinical diagnostic imaging results.     

Regional mixed-effects height–diameter models for loblolly pine (<Emphasis Type="Italic">Pinus taeda</Emphasis> L.) plantations

A height–diameter mixed-effects model was developed for loblolly pine (Pinus taeda L.) plantations in the southeastern US. Data were obtained from a region-wide thinning study established by the Loblolly Pine Growth and Yield Research Cooperative at Virginia Tech. The height–diameter model was based on an allometric function, which was linearized to include both fixed- and random-effects parameters. A test of regional-specific fixed-effects parameters indicated that separate equations were needed to estimate total tree heights in the Piedmont and Coastal Plain physiographic regions. The effect of sample size on the ability to estimate random-effects parameters in a new plot was analyzed. For both regions, an increase in the number of sample trees decreased the bias when the equation was applied to independent data. This investigation showed that the use of a calibrated response using one sample tree per plot makes the inclusion of additional predictor variables (e.g., stand density) unnecessary. A numerical example demonstrates the methodology used to predict random effects parameters, and thus, to estimate plot specific height–diameter relationships.     

An assessment of potential of hybrid poplar for planting in the Virginia Piedmont

Poplar species grow well across the temperate zone, but hybrid varieties have not previously been evaluated for planting in the Virginia Piedmont region. The top 12 clones in height growth and rust resistance from a screening trial involving 98 hybrid poplar varieties of three taxa (Populus deltoides × P. maximowiczii, DxM; P. deltoides × P. nigra, DxN; P. deltoides × P. trichocarpa, DxT) were selected for planting in replicated yield trials at two locations in the Virginia Piedmont. Results through the first four growing seasons showed that the DxM taxon had the most rapid height development. It was, however, the taxon most affected by a late spring frost at the Appomattox-Buckingham State Forest site and by Septoria stem canker at the Reynolds Homestead site. Analysis of variance of clonal and location effects showed highly significant differences among replicates within location and among clones within taxon. Among seven clones within the DxM taxon, pairwise comparison tests of height growth identified two groups: a group of four better clones that were significantly different (p = 0.05) from a second group of three. These early results suggest that multi-selection criteria, including growth, disease and frost resistance, are important when developing hybrid poplar clones for planting in the Piedmont region.     

木豆杂种优势利用研究进展

自1974年发现木豆雄性不育株以来,国际上不断对木豆核雄性不育(GMS)和核质互作雄性不育(CGMS)基因及其种质资源进行研究和挖掘,最终实现了木豆杂种优势的成功利用。本文系统总结了过去30多年来,国际上木豆杂种优势机理、表现及授粉方式等基础研究,GMS、CGMS不育系及其配套制种体系研究,杂种优势强度研究,以及木豆杂交种生产技术研究进展。提出了木豆杂种优势利用的具体研究方向和展望。     

Growth of young loblolly pine trees following pruning

Pruning loblolly pine trees is sometimes practiced to improve wood quality even though reduced growth following treatment may occur. Two experiments were established in February 2000 in the Piedmont region of Virginia, USA, to examine the impact of timing and intensity of pruning on subsequent growth of young loblolly pine trees. Results of one study indicated that there is a window of opportunity during the early portion of stand development where up to 50% of the live crown length can be removed without a significant loss of long-term height or diameter growth. Within a year following pruning at ages 3, 6 and 9 (all pruning treatments occurred prior to crown closure), crown mass had been restored and growth comparable to an unpruned control resumed. By age 11 there were no significant differences in cumulative height or dbh of any of the one-lift pruning treatments and the control. Findings from a second study planted at closer spacings where pruning treatments occurred at crown closure (age 6) showed that pruning some of the trees in a loblolly pine plantation does not result in a loss of long-term height or diameter growth or crown dominance for the pruned trees as compared to their unpruned neighbors. For both studies, growth reductions following pruning were small and transitory.     

Modulus of elasticity declines with decreasing planting density for loblolly pine (Pinus taeda) plantations

Context

Loblolly pine is often grown in intensively managed plantations for wood production. In order to fully evaluate the effects of management practices on wood quality and ultimately value, it is necessary to relate mechanical properties to management practices.

Aims

The aim of this study was to evaluate the effect of planting density on mechanical properties of lumber recovered from loblolly pine trees from a 27-year-old spacing trial and develop prediction equations for modulus of elasticity and modulus of rupture from stand, tree, and board characteristics.

Methods

Regression methods were applied to sample trees from three planting densities (2,989, 1,682, and 746 trees ha^?1) and used to relate mechanical properties of lumber extracted from the trees to stand, tree, and board characteristics.

Results

Initial planting density was found to be correlated with modulus of elasticity and, to a lesser extent, with modulus of rupture. Including board characteristics and utilizing the visual grade and board position as regressors produced improved prediction equations.

Conclusions

The mean modulus of elasticity declines with decreasing planting density while the variability increases, suggesting that planting density is a surrogate for frequency and size of knots. Thus, lower planting densities, while producing more lumber, may produce proportionally fewer boards of greater modulus of elasticity than higher planting densities.     

Modeling production and decay of coarse woody debris in loblolly pine plantations

Forest management can have large impacts on the production and yield of coarse woody debris (CWD) in terrestrial ecosystems, yet few modeling tools exist to inform such efforts. The goal here was to develop a set of prediction equations for use in conjunction with loblolly pine (Pinus taeda L.) modeling and inventory systems to estimate CWD yields at scales ranging from individual trees to whole plantations. Permanent field plots from a 21-year study of thinning effects on plantation growth and yield across the commercial range of the species in the southern United States were surveyed to obtain sample data on CWD volume, density, and mass. Measured CWD properties were combined with inventory records of tree mortality over the study duration to characterize CWD production, decay and yield in a series of prediction equations. The resulting equations predict CWD attributes of dead trees including dry weight (kg) and fraction of standing versus downed woody material based on the time since death (years), tree diameter at breast height (cm) and height (m) at time of death and geographic coordinates of latitude and longitude. A stand-level equation predicts total CWD yield (Mg ha⁻¹) for thinned or unthinned stands based on plantation age, stem density (trees ha⁻¹), and the average height of dominant and codominant trees (m). Piece-level equations predict dry density (kg m⁻³) or nitrogen concentration (%) of CWD pieces based on their position (standing or down), ordinal decay classes, and latitude. The tree and stand-level prediction equations are designed for use in GIS or growth and yield modeling systems. The piece-level equations are designed to be used in inventory applications that survey CWD. The equations should facilitate the accurate and facile determination of mass, carbon, and nitrogen contents of CWD in planted loblolly pine forests of the southern United States.