Identification of Orthotropic Elastic Properties of Wood by a Synthetic Image Approach Based on Digital Image Correlation

This work aims to determine the orthotropic linear elastic constitutive parameters of Pinus pinaster Ait. wood from a single uniaxial compressive experimental test, under quasi-static loading conditions, based on two different specimen configurations: (a) on-axis rectangular specimens oriented on the radial-tangential plane, (b) off-axis specimens with a grain angle of about 60(radial-tangential plane). Using digital image correlation (DIC), full-field displacement and strain maps are obtained and used to identify the four orthotropic elastic parameters using the finite element model updating (FEMU) technique. Based on the FE data, a synthetic image reconstruction approach is proposed by coupling the inverse identification method with synthetically deformed images, which are then processed by DIC and compared with the experimental results. The proposed methodology is first validated by employing a DIC-levelled FEA reference in the identification procedure. The impact of the DIC setting parameters on the identification results is systematically investigated. This influence appears to be stronger when the parameter is less sensitive to the experimental setup used. When using on-axis specimen configuration, three orthotropic parameters of Pinus pinaster (ER, ET and νRT) are correctly identified, while the shear modulus (GRT) is robustly identified when using off-axis specimen configuration.

UAV-Based LiDAR Scanning for Individual Tree Detection and Height Measurement in Young Forest Permanent Trials

The installation of research or permanent plots is a very common task in growth and forest yield research. At young ages, tree height is the most commonly measured variable, so the location of individuals is necessary when repeated measures are taken and if spatial analysis is required. Identifying the coordinates of individual trees and re-measuring the height of all trees is difficult and particularly costly (in time and money). The data used comes from three Pinus pinaster Ait. and three Pinus radiata D. Don plantations of 0.8 ha, with an age ranging between 2 and 5 years and mean heights between 1 and 5 m. Five individual tree detection (ITD) methods are evaluated, based on the Canopy Height Model (CHM), where the height of each tree is identified, and its crown is segmented. Three CHM resolutions are used for each method. All algorithms used for individual tree detection (ITD) tend to underestimate the number of trees. The best results are obtained with the R package, ForestTools and rLiDAR. The best CHM resolution for identifying trees was always 10 cm. We did not detect any differences in the relative error (RE) between Pinus pinaster and Pinus radiata. We found a pattern in the ITD depending on the height of the trees to be detected: the accuracy is lower when detecting trees less than 1 m high than when detecting larger trees (RE close to 12% versus 1% for taller trees). Regarding the estimation of tree height, we can conclude that the use of the CHM to estimate height tends to underestimate its value, while the use of the point cloud presents practically unbiased results. The stakeout of forestry research plots and the re-measurement of individual tree heights is an operation that can be performed by UAV-based LiDAR scanning sensors. The individual geolocation of each tree and the measurement of heights versus pole and/or hypsometer measurement is highly accurate and cost-effective, especially when tree height reaches 1–1.5 m.

Servicios ecosistémicos de masas mixtas de pino resinero y pino albar: conservación de la biodiversidad y secuestro de carbono

La mayoría de estudios sobre los efectos positivos de la mezcla de árboles en el contexto de suministro de servicios ecosistémicos (SE) se centran en mezclas que combinan especies diferentes. Sin embargo, este efecto es poco conocido cuando se mezclan especies del mismo género. Por ello, evaluamos el efecto de la mezcla sobre el suministro de SE en seis tripletes [6 tripletes×3 rodales (2 rodales puros+1 rodal mixto) =18 parcelas) de pino albar (Pinus sylvestris L.) y pino resinero (P. pinaster Ait.) en el noroeste de España. En cada parcela, el suelo (una calicata de 50cm de profundidad), el sotobosque (diez inventarios de 1x1m) y el estrato arbóreo (a dos escalas espaciales; escala de vecindario: diez inventarios de 4m de radio/parcela; escala de rodal: un inventario de 15m de radio/parcela) fueron analizados. Los resultados de esta tesis contribuyen a comprender los mecanismos involucrados en el suministro de SE en rodales puros vs. mixtos de P. sylvestris y P. pinaster: las masas mixtas presentan una ventaja competitiva sobre los rodales puros en términos de conservación de la biodiversidad, secuestro de carbono, fertilidad edáfica y producción del estrato arbóreo. Teniendo en cuenta que estas mezclas están ampliamente distribuidas en España, parece oportuno proponer que se sigan promoviendo ya contribuyen a incrementar la fertilidad del suelo, la acumulación de carbono, a proporcionar un exceso de área basal en relación con masas puras, y a conservar la regeneración de especies endémicas y mantenimiento de la riqueza del sotobosque en suelos con menor contenido hídrico. Palabras clave: masas mixtas, masas puras, Pinus sylvestris, Pinus pinaster, servicios ecosistémicos

Primary Metabolite Adjustments Associated With Pinewood Nematode Resistance in Pinus pinaster

The pinewood nematode (PWN) Bursaphelenchus xylophilus is the causal agent of the pine wilt disease (PWD) and represents one of the major threats to conifer forests. The detection of the PWN in Portugal, associated with Pinus pinaster, increased the concern of its spread to European forests. Despite its susceptibility to PWD, genetic variability found among P. pinaster populations has been associated with heritable PWD resistance. Understanding the mechanisms underlying tree resistance constitutes a valuable resource for breeding programs toward more resilient forest plantations. This study investigated changes in anatomy, chlorophyll a fluorescence (ChlF), and primary metabolism in susceptible and resistant P. pinaster half-sib plants, after PWN inoculation. Susceptible plants showed a general shutdown of central metabolism, osmolyte accumulation, photosynthetic inhibition, and a decrease in the plant water status. The ChlF transient rise (OJIP curve) revealed the appearance of L- and K-bands, indicators of environmental stress. In contrast, resistant plants revealed a regulated defense response and were able to restrict PWN migration and cellular damage. Furthermore, the accumulation of γ-aminobutyric acid (GABA) and succinate suggested a role of these metabolites in PWD resistance and the possible activation of the GABA shunt. Altogether, these results provide new insights to the role of primary metabolism in PWD resistance and in the selection of resistant phenotypes for disease mitigation.

Effect of Density on Mediterranean Pine Seedlings Using the Nelder Wheel Design: Analysis of Biomass Production

BackgroundForest resilience should be improved to promote species adaptation and ensure the future of forests. Carbon stock is considered an indicator of resilience, so it is necessary to determine forest carbon stocks and how to improve them through forest management. The main objective of this study was to analyse biomass production and distribution among the components of four-year-old Pinus pinaster and Pinus halepensis trees. Young trees from a Nelder wheel experimental site were harvested and analysed. The effect of density could be included in the biomass analysis thanks to the Nelder wheel design. We tested densities from 1000 to 80000 seedlings/ha and analysed biomass by fitting different equations: (i) linear regressions to analyse biomass production; (ii) Dirichlet regressions to estimate the biomass proportions of each component and (iii) allometric equations to predict the biomass content of each component.ResultsResults from this innovative approach showed that density was a significant factor for Pinus halepensis. We observed a general increase of total biomass at lower densities and this positive effect increased root biomass proportion at the expense of aboveground biomass. Also, a new set of equations was developed for estimating above- and below-ground biomass in young Pinus pinaster and Pinus halepensis trees.Conclusionswe note the importance of belowground biomass and its value in total biomass production (approximately 20% of total biomass for both species). The effect of density on biomass production was only significant for Pinus halepensis, but the effect of density would have been different if root biomass had not been considered in the present study. Lower densities increased root biomass proportion at the expense of aboveground biomass. Currently, this positive effect is especially important in promoting management to improve tree resilience.