Once forests have achieved a full canopy, their growth rate declines progressively with age. This work used a global data set with estimates from a wide range of forest types, aged 20‒795 years, of their annual photosynthetic production (gross primary production, GPP) and subsequent above- plus below-ground biomass production (net primary production, NPP). Both GPP and NPP increased with increasing mean annual temperature and precipitation. GPP was then unrelated to forest age whilst NPP declined progressively with increasing age. These results implied that autotrophic respiration increases with age. It has been proposed that GPP should decline in response to increasing water stress in leaves as water is raised to greater heights as trees grow taller with age. However, trees may make substantial plastic adjustment in morphology and anatomy of newly developing leaves, xylem and fine roots to compensate for this stress and maintain GPP with age. This work reviews the possibilities that NPP declines with age as respiratory costs increase progressively in, any or all of, the construction and maintenance of more complex tissues, the maintenance of increasing amounts of live tissue within the sapwood of stems and coarse roots, the conversion of sapwood to heartwood, the increasing distance of phloem transport, increased turnover rates of fine roots, cost of supporting very tall trees that are unable to compensate fully for increased water stress in their canopies or maintaining alive competitively unsuccessful small trees.

Abiotic and biotic factors that cause damage to forest trees also threaten the sustainability of forest resources. Although winter storms can be one of the most damaging forces, very few studies have focused on winter storm damage in Turkey. To prevent or minimize storm damage, we must evaluate the factors that influence the degree of damage and develop storm risk maps for the forested areas. Here, a GIS-based mathematical model (fuzzy logic) was used to develop such a risk map by considering risk factors such as tree species, tree age, crown density, site quality, topographical features (elevation, slope, aspect), climatic variables (wind, precipitation), and soil depth. The Alabarda Forest Enterprise Chief within the borders of Tavşanlı Forest Enterprise Directorate was selected as the study area due to high occurrence of storm damage in the region during winter 2015–2016. For model verification, the risk map of storm damage was compared to the actual areal distribution of storm damage reported by the Enterprise Directorate. The model based on fuzzy logic indicated that slightly more than half of the study area (52.49%) was under very low storm damage risk, 28.12% was under low risk and 19.19% was classified as high risk. A very small portion of the total study area was classified as very high risk. These results indicated a close relation with the storm damage map generated using Tavşanlı FED records. The results revealed that the most effective risk predictors for overall storm damage risk were wind direction and speed, followed by slope and site quality factors.

Seeds of Elaeagnus mollis (Elaeagnaceae) produce an edible oil and contain more vitamin E (Ve) than major oil-seed crops. Despite its economic value, there is no information on its genome sequence. Here, we used the Illumina platform to determine the seed transcriptome of E. mollis to identify the genes related to Ve biosynthesis and potential simple sequence repeat (SSR) markers. In total, 100,999 unigenes were obtained with an average length of 605 bp and N50 of 985 bp. Of these unigenes, 52,256 (51.7%) were annotated in at least one public database (NT, NR, PFAM, SwissProt, KOG, KO, and GO) in searches using blastn/x. The unigene annotation identified 15 unigenes encoding six enzymes (GGR, HPPD, HPT/VTE2, MPBQ-MT/VTE3, TC/VTE1, and γ-TMT/VTE4) putatively involved in Ve biosynthesis. In addition, 16,810 SSRs distributed in 14,057 unigenes were mined. Of these, 2820, 583, and 3423 SSRs were located in the 5′–UTR, coding sequence (CDS), and 3′–UTR regions, respectively, while the remaining 9984 SSRs had undetermined physical locations. The largest group of repeat motifs comprised mononucleotide repeats (70.76%), followed by dinucleotide (15.59%) and trinucleotide (12.10%) repeats. AG/CT (8.69%) and AAG/CTT (4.15%) were the main dinucleotide and trinucleotide repeats, respectively. Furthermore, 9597 SSR-specific primer pairs were designed. Among 100 primer pairs selected randomly to determine their usefulness, 53 proved to be efficient. To the our best of knowledge, this work is the first study of the E. mollis transcriptome and constitutes valuable genomics data for future genetic engineering studies to alter the amount of Ve. The identified potential EST-SSR markers can be used for population genetics studies and assisted-breeding of E. mollis.

This research investigates the mechanism of increased salinity tolerance of ectomycorrhizal fungi-inoculated P. sylvestris var. mongolica to provide a theoretical basis for the application of the fungus in saline soils. Growth effects due to inoculation of seedlings with Suillus luteus (a symbiotic ectomycorrhizal fungus), were determined in four kinds of saline–alkali soils. Growth and physiological indicators, including photosynthetic characteristics, plant height, biomass, photosynthetic pigments, catalase (CAT) and superoxide dismutase (SOD) enzyme levels, and malondialdehyde (MDA), an organic marker for oxidative stress, and soluble protein levels were determined. Mycorrhizal colonization rate decreased with increasing saline–alkalinity and growth of inoculated seedlings was significantly enhanced. Biomass and chlorophyll contents also increased significantly. SOD and CAT activities were higher than in non-inoculated seedlings. However, MDA content decreased in inoculated seedlings. Soluble protein content did not increase significantly. Inoculation with a symbiotic ectomycorrhizal fungus could enhance the saline–alkali tolerance of P. sylvestris var. mongolica. Growth and physiological performance of inoculated seedlings were significantly better than that of uninoculated seedlings. The results indicate that inoculated P. sylvestris var. mongolica seedlings may be useful in the improvement of saline–alkali lands.

Drought is considered the main environmental factor limiting productivity in eucalyptus plantations in Brazil. However, recent studies have reported that exposure to water deficit conditions enables plants to respond to subsequent stresses. Thus, this study investigates the ecophysiological acclimatization of eucalyptus clones submitted to recurrent water deficit cycles. Eucalyptus seedlings were submitted to three recurrent water deficit cycles and anatomical, morphological and physiological changes were analyzed. The results were: (1) Eucalyptus seedlings responded to water deficits by directing carbohydrates to root and stem growth; (2) Size and number of stomata were reduced; (3) Stomatal conductance decreased which allowed the plants to reduce water losses through transpiration, increasing instantaneous water use efficiency; (4) The relationship between gas exchanges and available water contents allowed the seedlings to uptake the retained soil water at higher tensions; and, (5) Physiological recovery from subsequent water deficits became faster. As a result of these changes, the eucalyptus seedlings recovered from the same degree of water stress more rapidly.

A comprehensive experimental design was developed to determine suitable conditions (volume, percentage of solvent, extraction temperature) for the ethanol extraction of phenolic compounds from ten tropical woody plants. Wenge, angelim vermelho, zebrano, merbau, tigerwood, angelim pedra, jatoba, angelim amargoso, massaranduba, and doussie woods were used in experiments. The effects of three independent variables and their interactions on the yields of cinnamic and benzoic acid derivates were analyzed using UHPLC-PDA. The most significant parameters were found to be solvent percentage, extraction volume, and extraction temperature. Optimal conditions for the extraction of phenolic compound contents were an 80 °C extraction temperature, a 30 mL extraction volume, and the use of pure water as the extraction solvent. The tested species of woods contained mainly cinnamic acid derivates. Water extracts after hydrolysis contained greater amounts of cinnamic acid derivates than those extracts from non-hydrolyzed material. The total phenolics content was highest in water extracts of tigerwood, wenge and merbau; however, the extract of merbau wood was a stronger radical scavenger in ABTS^+· assays: 34.11 ± 0.02 mM Trolox equivalents per g of dry extract. The main compounds possessing antioxidant activity in the extracts of vermelho wood assessed by UHPLC analysis were hydroxycinnamic acids.

The structural characteristics of the tree crowns of Cunninghamia lanceolata var. Luotian (herein, Luotian), a natural variety of C. lanceolata (Chinese-fir, herein Lanceolata) in China, were analyzed using trunk and branch measurements and biomass determinations. Samples from two typical cultivated varietal populations were collected, including twenty-six 15–23-year-old trees of Luotian from a plantation, and nine 16–23-year-old trees of Lanceolata. Our results show that Luotian and Lanceolata samples differed significantly in crown structure, morphological indices, and biomass: (1) the oldest live branches on Luotian trees were 5–6 years old and 8–11 years old on Lanceolata. The ages of the live branches were not affected by the ages of the Luotian trees, while live branch ages increased with ages of Lanceolata trees; (2) the maximum branching order of Luotian was level two. Compared to Lanceolata, the average number of first-order lateral branches (i.e., branches emerging from the trunk) and the number of first-order lateral branch whorls per sample tree were 12.9% and 32.2% lower, respectively, in Luotian. However, the average number of branches within a single whorl was 21.8% greater in Luotian; the average number of branch whorls at crown height was 51.1% greater. Thus, the Luotian variety has thicker branches; (3) the average lateral branch angles in Luotian and Lanceolata sample trees were 105.2° and 61.4°, respectively. The branch angles in 53.0% of lateral branches on Luotian ranged from 105° to 135°, but 30° to 90° in 96% of the lateral branches on Lanceolata. Within the same crown layer, the average branch angle was 1.6–2.2 times greater in Luotian, and the angle was directly proportional to crown thickness; (4) the average base diameter and branch length on Luotian were 1.3 cm and 75.8 cm, respectively, and 1.6 cm and 112.2 cm for Lanceolata. For individual trees, branch growth differed significantly (p < 0.01) between Luotian and Lanceolata. However, the lateral branches grew at a similar rate among Luotian trees of different ages; (5) the average height to the lowest live branch on Luotian was 128.3% greater than on Lanceolata, resulting in a significant difference (p < 0.01) in crown size. Compared to the crowns on Lanceolata, the Luotian crowns were 45.3% higher and 41.1% wider, and the surface area, volume, and growth of the crown were 27.0%, 11.4%, and 2.4 times greater than for Lanceolata, respectively; and, (6) the biomass of Luotian and Lanceolata sample trees also differed significantly. The mean crown, branch, and leaf biomass for Luotian was 40.0%, 25.2%, and 54.1% of those for Lanceolata, respectively. However, the leaf biomass in each layer of the Luotian crown was higher than that of Lanceolata, and leaf biomass increased with crown thickness.

Quantifying fine root (≤ 2.0 mm in diameter) distribution and turnover is essential for accurately estimating forest carbon budgets. However, fine root dynamics are poorly understood, possibly because of their inaccessibility. This study quantifies fine root distribution and turnover rates for five representative Chinese temperate forests types. Fine root number, diameter, biomass, necromass, production, mortality, and turnover rates were measured using a minirhizotron over a 12-month period. More than 90% of the fine roots were < 0.5 mm in diameter, with thin fine roots at shallow layers, and thicker ones in deeper soil layers. The fine root dynamics were significantly different among the forest types. Coniferous plantations had fewer fine roots, less biomass, necromass, production and mortality but greater average diameters than fine roots of broadleaved forests. All traits, except for diameter, decreased along the soil profile. Fine root numbers and production exhibited a unimodal seasonal pattern with peaks occurring in summer, whereas biomass, necromass and mortality progressively increased over the growing season. The turnover rates of roots < 0.5 mm varied from 0.4 to 1.0 a⁻¹ for the five forest types, 0.5–1.0 a⁻¹ for the soil layers and 0.2–1.1 a⁻¹ for the seasons, with the largest turnover rate at the 0–10 cm depth in summer. The patterns of fine root numbers, biomass, necromass, production, mortality, and turnover rates varied with forest types, soil depths, growing season and diameter classes. This study highlights the importance of forest types and diameters in quantifying fine root turnover rates.

Eucalyptus camaldulensis Dehnh. and E. globulus Labill. are economically important species for wood and pulpwood materials. Representative heights for assessing whole-tree values of cell-type proportions (vessels, fibers, ray and axial parenchyma percentages) using increment cores were examined by analysis of within-tree variations. Pattern differences were evaluated between trees and species in both radial and axial directions by statistical data analysis (Moses test). In E. camaldulensis, within-tree variation of vessel percentage was generally higher in the upper and outer regions of the trunk. In contrast, E. globulus within-tree variation was unclear. In both species, although no clear pattern of fiber percentages was observed, within-tree variations of ray and axial parenchyma levels were higher in the lower and inner regions. Significant differences in patterns were observed in the axial variation between species for vessel percentages and in the radial variation between trees of E. camaldulensis for ray parenchyma percentages. The representative heights for assessing whole-tree cell-type proportions were 0.8 m above the ground for E. camaldulensis and 2.8 m for E. globulus, regardless of differences in tree height and pattern of within-tree variation of cell-type proportions.

Teak (Tectona grandis Linn. f.), one of the most-valued tree species in the world, is slow-growing with a long period until it can be harvested; therefore, ensuring that only high-quality seedlings or clones are selected for planting is critical. The main objective was to determine performance and repeatability of selected clones in terms of growth and survival rates in different micro-environments. A 2-year clonal trial using 41 clones and a local seedling of teak as a control were grown at 4 microsites differing in spacing, soil fertility and alley crops to assess tree height, diameter and survival rate that was evaluated in Purwakarta, West Java, Indonesia using a randomized complete block design with four replicates of each clone at each microsite. Teak growth was influenced by clone (p < 0.01), microsite (p < 0.05) and clone × microsite interaction (p < 0.01). The interaction clone × microsite resulted in several potential superior clones that differed in terms of growth rates at each microsite. On the basis of diameter only, superior clones (nos. 14, 18, 24, 30 and 37) were identified. Repeatability estimated was R _c ² = 0.84 for diameter and R _c ² = 0.77 for height. Growth performance of teak trees varied among microsites. Repeatability values for diameter and height characters were high. The effect of variable growth on each clone was influenced by genetic factors, environmental factors and the interaction of genetics × environment. Microsite significantly affected growth of teak clones. Clone × microsite interaction significantly affected growth of clones and led to the growth of superior clones at each microsite.

Myeloblastosis (MYB) proteins constitute one of the largest transcription factor (TF) families in plants and play crucial roles in regulating plant physiological and biochemical processes, including adaptation to diverse abiotic stresses. These TF families contain highly conserved MYB repeats (1R, R2R3, 3R and 4R) at the N-terminus. Roles for MYB TFs have been reported in response to such stresses as dehydration, salt, cold, and drought. The characterization of Masson pine (Pinus massoniana) MYB TFs are reported, including the analysis of MYB TFs expression in seedlings under controlled conditions and two different phosphate (Pi) deficient treatments. By searching for conserved MYB motifs in full transcriptomic RNA sequencing data for P. massoniana, 59 sequences were identified as MYB TFs. Conserved domain structures and comparative functional and phylogenetic relationships of these MYB TFs with those in Arabidopsis were assessed using various bioinformatics tools. Based on microarray analysis, P. massoniana MYB genes exhibited different expression patterns under the two Pi deficiency conditions. Genes encoding MYB TFs that showed increased expression under critical Pi deficiency were identified, and some MYBs were differentially expressed only under conditions of severe Pi starvation. These results are useful for the functional characterization of MYB TFs that may be involved in the response to Pi deficiency and play divergent roles in plants.

The population structure and regeneration status of Magnolia punduana Hk. f. & Th., an endemic tree species of northeast India were investigated in fragmented forests in the Jarain Hills and in adjoining areas of Meghalaya state. The population structure was discontinuous in all the fragments with the absence of individuals in higher diameter classes. The number of individuals increased with the size of the fragment patches (p < 0.004). The density of mature trees (≥ 5 cm dbh) was high (24–30 individuals ha⁻¹) in the largest fragment (> 105 ha). The number of seedlings and saplings were also higher in the larger fragments. Human-related disturbances had a negative impact on the species population (p < 0.002). Variation in the population density in different forest patches has been attributed to fragment size, site characteristics and ongoing human disturbances. The restricted distribution of the species coupled with exploitation and habitat destruction underlines the need for its conservation.

Litterfall, which is influenced by physical and biological factors, is a major pathway for carbon and nutrient cycling in forest ecosystems. The purpose of this study was to investigate monthly litterfall production in three forests in Jeju Island differentiated by forest composition and precipitation: Cheongsu (Quercus glauca as the dominant species; low precipitation), Seonheul_b (Q. glauca as the dominant species; high precipitation), and Seonheul_m (Q. glauca and Pinus thunbergii as the dominant species; high precipitation). Litterfall was collected monthly from April to December 2015 and divided into leaf litter, twig, bark, seeds, and unidentified materials. Seasonal patterns of litterfall production varied across stands according to their species composition. However, the amount of leaf litterfall and total litterfall were comparable among stands, ranging from 362 to 375 g m⁻² for leaf litter and 524 g m⁻² to 580 g m⁻² for total litterfall. Oak leaf litter in May was the highest in all stands, while needle litter was the highest in December in Seonheul_m. High twig litterfall in July may be attributable to high rainfall with strong winds and storms during the rainy season. Although forest type and climate factor had no influence on litterfall amounts in this study, the pattern of litterfall production was species dependent, suggesting diverse effects on carbon and nutrient cycling in these forests.

In a survey of the Bore–Anferara–Wadera forest to study the vegetation structure and regeneration status of woody plant species, 112 quadrats were systematically sampled along altitudinal transects to collect vegetation data. Nested sample plots of 30 m × 30 m and 5 m × 5 m were laid for collecting data on abundance and some variables of tree and shrub size. The regeneration status of woody species was assessed by counting all seedlings within the main sample plot. Woody plant species taller than or equal to 3 m were counted and their height and DBH measured. Density, frequency, basal area and importance value (IV) of woody plant species were computed. A total of 136 vascular plant species belonging to 119 genera and 63 families were recorded. The overall Shannon—Wiener diversity value was 3.84 and evenness was 0.78. Total density of trees and shrubs with DBH > 2 cm was 1047 ha⁻¹. Size class distribution of woody species across different DBH and height classes indicated a relatively high proportion of individuals at lower classes, suggesting impacts of past anthropogenic disturbances. Analysis of population structure and regeneration status of the forest revealed various patterns of population dynamics where some species were represented by only a few mature plants, suggesting that they are on the verge of local extinction and that immediate conservation measures should be taken. The results highlight the need for joint management and conservation measures by the government, local people and other stakeholders to abate the rapid rate of deforestation and promote sustainable utilization of the forest resources in this forest in southern Ethiopia.

The effects of vegetation restoration on matrix structure and erosion resistance of iron tailings were studied at dump sites in Malanzhuang, Qian’an, Hebei province, China. The restoration process involved soil spray sowing restoration model with Rhus typhina, soil and iron tailings admixture spray sowing restoration model with Amorpha fruticosa Linn. and six-hole brick restoration model with Pinus tabulaeformis Carrière.–Amorpha fruticosa Linn. mixed-forest, and direct restoration model with Hippophae rhamnoides and Sabina vulgaris. Results show that the composition and distribution of particles and aggregates were closely related to erosion resistance (P < 0.05), indicating that matrix structure of iron tailings play an important role in erosion resistance. The improvement in matrix structure of iron tailings by the different restoration models was in the order of R. typhina soil spray sowing >  A. fruticosa soil and iron tailings admixture spray sowing > mixed-forest six-hole brick >  H. rhamnoides direct restoration >  S. vulgaris direct restoration. The R. typhina soil spray sowing restoration model resulted in the greatest improvement in matrix structure of iron tailings, increasing the clay (10.6%) and large particle aggregates (18.7%) contents significantly (P < 0.01). Simultaneously, particle population, grading conditions (C _u = 28.86, C _s = 1.65), and aggregate stability (6.02) were significantly improved. The A. fruticosa soil and iron tailings admixture spray sowing restoration model, which effectively improved particle distribution (C _u = 8.51, C _s = 1.07), increased the number of large aggregates considerably (9.6%), thereby increasing aggregate stability (6.2). The six-hole brick model significantly increased the number of large aggregates (4.0%) and improved the stability of aggregates (6.2). H. rhamnoides direct restoration improved the stability of aggregates (5.1) but showed no other significant improvements. The effect of S. vulgaris direct restoration on matrix structure of iron tailings was not significant. Due to its dependence on matrix structure of iron tailings, the erosion resistance of R. typhina soil spray sowing restoration model was the greatest, while that of S. vulgaris direct restoration was the weakest. There was no significant difference in the erosion resistance of the other models. Overall, vegetation restoration supplemented by soil spray sowing restoration and engineering measures is superior to in situ direct vegetation restoration in the short-term. In-situ direct restoration has long-term ecological significance because of its advanced concept of near-natural restoration and the advantages of low cost, easy operation, and low secondary damage.

The purpose of this study was to quantify the changes in tree diversity and above-ground biomass associated with six land-use types in Kodagu district of India’s Western Ghats. We collected data on species richness, composition and above-ground biomass (AGB) of trees, shrubs and herbs from 96 sample plots of 0.1 ha. Totals of 83 species from 26 families were recorded across the land-uses. Tree species richness, diversity and composition were significantly higher in evergreen forest (EGF) than in other land-uses. Similarly, stem density and basal area were greater in EGF compared to other land-uses. Detrended correspondence analysis (DCA) yielded three distinct groups along the land-use intensities and rainfall gradient on the first and second axes, respectively. The first DCA axis accounted for 45% and second axis for 35% of the total variation in species composition. Together the first two axes accounted for over 2/3 of the variation in species composition across land-use types. Across the land-uses, AGB ranged from 58.6 Mg ha⁻¹ in rubber plantation to 327.3 Mg ha⁻¹ in evergreen forest. Our results showed that species diversity and AGB were negatively impacted by the land-use changes. We found that coffee agroforests resembled natural forest and mixed species plantation in terms of tree diversity and biomass production, suggesting that traditional coffee farms can help to protect tree species, sustain smallholder production and offer opportunities for conservation of biodiversity and climate change mitigation.

We studied infiltration and fractal mechanisms on sloping farmlands in a small watershed in Shandong Province in the rocky mountain areas of northern China. We studied soil fraction and soil water retention curves, and developed a soil infiltration model to analyze its quantitative relationship with soil particle size and pore dimensions under four types of land use, including sloping farmland, abandoned land, natural forest, and forest plantation (Malus pumila, Crataegus pinnatifida). Soil stability infiltration rate ranked as sloping farmland > abandoned land > natural forest > forest plantation. The sequence of soil particle size and pore dimension ranked as natural forest > forest plantation > abandoned land > sloping farmland. There were significant positive correlations between soil particle size and pore dimension, and both were positively correlated with the percent volume of silt and clay. They were negatively correlated with soil infiltration rate. The Horton model and the power function model were more suitable for simulating soil infiltration and the infiltration rate. We concluded that the soil in this area displayed typical fragments of rocky mountainous regions due to the loss of silt and clay caused by cultivation on sloping farmland. The uniformity and fractal dimensions of soil particle sizes and pore distribution decreased, thereby enhancing soil infiltration capacity and decreasing soil water retention capacity.

Floodplain forests with regular flooding regimes are the largest natural retentions areas in Croatia and are important as natural habitats for ungulates. The aim of this study was to determine the scale of mortality caused by flooding within these forests. Over a 10-year period, data on ungulate mortality (red deer, roe deer and wild boar), flood duration and flooded surface area were recorded. The study was conducted in primary (Posavske Šume—RET I) and secondary (Opeke II—RET II) retention areas within Lonjsko Polje Nature Park (Sava River region, Croatia). The longest flood period and the largest flooded surface area were recorded in RET I. Total ungulate mortality was 749 individuals, with 482 individuals in RET I and 267 individuals in RET II, predominantly wild boar. Flood mortality did not differ by gender. The highest mortality of wild boar was recorded for the juvenile and yearling age classes. Low mortality of red and roe deer can be attributed to their body size and ecological niches. Differences in mortality between the primary and secondary retention areas corresponded to differences in flood regimes, flood column heights and micro relief structures. In both retention areas, wild boar mortality and flood duration, i.e. flooded surface area, were positively correlated. Because the growth rate of the analysed ungulate populations was higher than the recorded mortality, no long-term effect of floods is expected on species abundance in these areas.

This study used near-infrared (NIR) spectroscopy to predict mechanical properties of wood. NIR spectra were collected in wavelengths 900–1700 nm, and spectra averaged by radial and tangential surface spectra were used to establish a partial least square (PLS) model based on correlation local embedding (CLE). Mongolian oak (Quercus mongolica Fisch. ex Ledeb.) was used to test the effectiveness of the model. The cross-validation method was used to verify the robustness of the CLE–PLS model. Ninety samples were tested as the calibration set and forty-five as the validation set. The results show that the prediction coefficient of determination (

A transfer learning system was designed to predict Xylosma racemosum compression strength. Near-infrared (NIR) spectral data for Acer mono and its compression strength values were used to resolve the weak generalization problem caused by using a X. racemosum dataset alone. Transfer component analysis and principal component analysis are domain adaption and feature extraction processes to enable the use of A. mono NIR spectral data to design the transfer learning system. A five-layer neural network relevant to the X. racemosum dataset, was fine-tuned using the A. mono dataset. There were 109 A. mono samples used as the source dataset and 79 X. racemosum samples as the target dataset. When the ratio of the training set to the test set was 1:9, the correlation coefficient was 0.88, and mean square error was 8.84. The results show that NIR spectral data of hardwood species are related. Predicting the mechanical strength of hardwood species using multi-species NIR spectral datasets will improve the generalization ability of the model and increase accuracy.

Eucalyptus urophylla, Acacia mangium, and Pinus caribaea are the primary species for the wood industry in Vietnam. Wood residues of these species were used to reinforce high-density polyethylene (HDPE) composites. The flexural or bending property, impact strength and surface color were evaluated after exposure to accelerated ultraviolet weathering up to 2000 h. The weathered surface was characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The results indicate that A. mangium/HDPE composites had the lowest color change and least fading, and remained stable after 1500 h exposure. FTIR spectroscopy showed that the oxidation of the composites increased in parallel with duration of exposure by assessing the concentration of carbonyl groups on the surfaces. SEM showed that all three species reinforced composites exhibited similar severe cracks after 1000 h; however, at the end of the weathering test, E. urophylla and P. caribaea composites were more severely cracked than A. mangium composites. A. mangium also had the highest flexural strength, impact strength and crystallinity during weathering. A. mangium is the most preferable among the three species to reinforce HDPE.