Functional trade-offs are driven by coordinated changes among cell types in the wood of angiosperm trees from different climates.

Wood performs several functions to ensure tree survival and carbon allocation to a finite stem volume leads to trade-offs among cell types. It is not known to what extent these trade-offs modify functional trade-offs and if they are consistent across climates and evolutionary lineages. Twelve wood traits were measured in stems and coarse roots across 60 adult angiosperm tree species from temperate, Mediterranean and tropical climates. Regardless of climate, clear trade-offs occurred among cellular fractions, but did not translate into specific functional trade-offs. Wood density was negatively related to hydraulic conductivity (Kth ) in stems and roots, but was not linked to nonstructural carbohydrates (NSC), implying a functional trade-off between mechanical integrity and transport but not with storage. NSC storage capacity was positively associated with Kth in stems and negatively in roots, reflecting a potential role for NSC in the maintenance of hydraulic integrity in stems but not in roots. Results of phylogenetic analyses suggest that evolutionary histories cannot explain covariations among traits. Trade-offs occur among cellular fractions, without necessarily modifying trade-offs in function. However, functional trade-offs are driven by coordinated changes among xylem cell types depending on the dominant role of each cell type in stems and roots.

Non-structural carbohydrates and morphological traits of leaves, stems and roots from tree species in different climates.

OBJECTIVES: Carbon fixed during photosynthesis is exported from leaves towards sink organs as non-structural carbohydrates (NSC), that are a key energy source for metabolic processes in trees. In xylem, NSC are mostly stored as soluble sugars and starch in radial and axial parenchyma. The multi-functional nature of xylem means that cells possess several functions, including water transport, storage and mechanical support. Little is known about how NSC impacts xylem multi-functionality, nor how NSC vary among species and climates. We collected leaves, stem and root xylem from tree species growing in three climates and estimated NSC in each organ. We also measured xylem traits linked to hydraulic and mechanical functioning. DATA DESCRIPTION: The paper describes functional traits in leaves, stems and roots, including NSC, carbon, nitrogen, specific leaf area, stem and root wood density and xylem traits. Data are provided for up to 90 angiosperm species from temperate, Mediterranean and tropical climates. These data are useful for understanding the trade-offs in resource allocation from a whole-plant perspective, and to better quantify xylem structure and function related to water transportation, mechanical support and storage. Data will also give researchers keys to understanding the ability of trees to adjust to a changing climate.

Quantitative parametric imaging by ultrasound computed tomography of trees under anisotropic conditions: Numerical case study.

A method for the reconstruction of 2D tomographic images adapted to wood was presented, aiming to perform a nondestructive evaluation of standing trees. The proposed method takes into account the orthotropy property of wood material, performing an iterative process that approximated the curved rays. A slowness function was defined for every cell and a nonlinear regression allowed the mapping of the inner elastic constants. Four numerical configurations were tested representing real cases usually found in standing tree monitoring. These specific configurations allowed this work to focus on the analysis of the effect of anisotropy on image reconstruction. The reconstructed images using the proposed method were compared with a straight-ray reconstruction method (filtered back projection algorithm), highlighting a more detailed identification and quantification of the inner state of the anisotropic structure of the trunk.

Effect of wood anisotropy in ultrasonic wave propagation: A ray-tracing approach.

Ultrasonic nondestructive imaging methods allow analyzing the inner structures of trees, without altering their condition. In this study, we are interested in evaluating the influence of anisotropy condition in the wood on the ultrasonic waves time-of-flight (TOF) estimation, by means of a raytracing approach. This technique is used particularly in the field of exploration seismography to simulate wavefronts in elastic media. Wood sections from two species were tested. Defects in the wood were simulated by drilling holes. Defects were tested in two positions, centric and eccentric, and three different defect diameters were used for each position. First, experiments with healthy wood showed that the orthotropic behavior resulted in curved rays from the transmitter to every receiver, compared to the straight-line paths for the isotropic case, considering that the radial direction presents a higher wave velocity. Defects inside the wood resulted in low velocity propagation areas, that modified the trajectories compared to the healthy case. Centric defects resulted in larger TOF variations than eccentric defects. A combination of centric position and bigger size corresponded to a higher probability of decay detection using a tomographic image. To increase the tomographic image quality, curved rays should be considered when performing the image reconstruction.

Accuracy of coded excitation methods for measuring the time of flight: Application to ultrasonic characterization of wood samples.

Ultrasound computed tomography (USCT) using the transmission mode is a way to detect and assess the extent of decay in wood structures. The resolution of the ultrasonic image is closely related to the different anatomical features of wood. The complexity of the wave propagation process generates complex signals consisting of several wave packets with different signatures. Wave paths, depth dependencies, wave velocities or attenuations are often difficult to interpret. For this kind of assessment, the focus is generally on signal pre-processing. Several approaches have been used so far including filtering, spectrum analysis and a method involving deconvolution using a characteristic transfer function of the experimental device. However, all these approaches may be too sophisticated and/or unstable. The alternative methods proposed in this work are based on coded excitation, which makes it possible to process both local and general information available such as frequency and time parameters. Coded excitation is based on the filtering of the transmitted signal using a suitable electric input signal. The aim of the present study was to compare two coded-excitation methods, a chirp- and a wavelet-coded excitation method, to determine the time of flight of the ultrasonic wave, and to investigate the feasibility, the robustness and the precision of the measurement of geometrical and acoustical properties in laboratory conditions. To obtain control experimental data, the two methods were compared with the conventional ultrasonic pulse method. Experiments were conducted on a polyurethane resin sample and two samples of different wood species using two 500 kHz-transducers. The relative errors in the measurement of thickness compared with the results of caliper measurements ranged from 0.13% minimum for the wavelet-coded excitation method to 2.3% maximum for the chirp-coded excitation method. For the relative errors in the measurement of ultrasonic wave velocity, the coded excitation methods showed differences ranging from 0.24% minimum for the wavelet-coded excitation method to 2.62% maximum for the chirp-coded excitation method. Methods based on coded excitation algorithms thus enable accurate measurements of thickness and ultrasonic wave velocity in samples of wood species.

Stochastic modelling of tree architecture and biomass allocation: application to teak (Tectona grandis L. f.), a tree species with polycyclic growth and leaf neoformation.

Background and aims: For a given genotype, the observed variability of tree forms results from the stochasticity of meristem functioning and from changing and heterogeneous environmental factors affecting biomass formation and allocation. In response to climate change, trees adapt their architecture by adjusting growth processes such as pre- and neoformation, as well as polycyclic growth. This is the case for the teak tree. The aim of this work was to adapt the plant model, GreenLab, in order to take into consideration both these processes using existing data on this tree species. Methods: This work adopted GreenLab formalism based on source-sink relationships at organ level that drive biomass production and partitioning within the whole plant over time. The stochastic aspect of phytomer production can be modelled by a Bernoulli process. The teak model was designed, parameterized and analysed using the architectural data from 2- to 5-year-old teak trees in open field stands. Key results: Growth and development parameters were identified, fitting the observed compound organic series with the theoretical series, using generalized least squares methods. Phytomer distributions of growth units and branching pattern varied depending on their axis category, i.e. their physiological age. These emerging properties were in accordance with the observed growth patterns and biomass allocation dynamics during a growing season marked by a short dry season. Conclusions: Annual growth patterns observed on teak, including shoot pre- and neoformation and polycyclism, were reproduced by the new version of the GreenLab model. However, further updating is discussed in order to ensure better consideration of radial variation in basic specific gravity of wood. Such upgrading of the model will enable teak ideotypes to be defined for improving wood production in terms of both volume and quality.

Integrated dataset of anatomical, morphological, and architectural traits for plant species in Madagascar.

In this work, we present a dataset, which provides information on the structural diversity of some endemic tropical species in Madagascar. The data were from CIRAD xylotheque (since 1937), and were also collected during various fieldworks (since 1964). The field notes and photographs were provided by French botanists; particularly by Francis Hallé. The dataset covers 250 plant species with anatomical, morphological, and architectural traits indexed from digitized wood slides and fieldwork documents. The digitized wood slides were constituted by the transverse, tangential, and radial sections with three optical magnifications. The main specific anatomical traits can be found within the digitized area. Information on morphological and architectural traits were indexed from digitized field drawings including notes and photographs. The data are hosted in the website ArchiWood (http://archiwood.cirad.fr).

Sound quality assessment of wood for xylophone bars.

Xylophone sounds produced by striking wooden bars with a mallet are strongly influenced by the mechanical properties of the wood species chosen by the xylophone maker. In this paper, we address the relationship between the sound quality based on the timbre attribute of impacted wooden bars and the physical parameters characterizing wood species. For this, a methodology is proposed that associates an analysis-synthesis process and a perceptual classification test. Sounds generated by impacting 59 wooden bars of different species but with the same geometry were recorded and classified by a renowned instrument maker. The sounds were further digitally processed and adjusted to the same pitch before being once again classified. The processing is based on a physical model ensuring the main characteristics of the wood are preserved during the sound transformation. Statistical analysis of both classifications showed the influence of the pitch in the xylophone maker judgement and pointed out the importance of two timbre descriptors: the frequency-dependent damping and the spectral bandwidth. These descriptors are linked with physical and anatomical characteristics of wood species, providing new clues in the choice of attractive wood species from a musical point of view.