Wood Growth Research Articles

Soil Effects on Stem Growth and Wood Anatomy of Tamboril Are Mediated by Tree Age

Soil influences the growth of trees and the characteristics of the wood; but could this influence change during the ontogeny of trees? To answer this question, we analyzed the wood anatomy of 9-year-old trees and 2-year-old saplings of Enterolobium contortisiliquum, known as “tamboril”, growing in eutrophic and oligotrophic soil in the Brazilian Cerrado, and assessed the effect of age on plant–soil relationship. Sapwood samples were collected from the main stem, anatomical sections were prepared in the lab, and 12 anatomical wood traits were measured. Individuals in eutrophic soil had greater stem diameter and height than those in oligotrophic soil. Trees in eutrophic soil had vessel-associated parenchyma cells with abundant storage compounds. Fibers walls were 47% thicker and intervessel pits diameter were 14% larger in trees of eutrophic soil. A greater proportion of solitary vessels (74%) was observed in trees rather than in saplings (50%). The secondary xylem of trees was mainly formed by fibers (63%) whereas in saplings it was mainly formed by storage tissue (64%). Our study provides evidence that the influence of soil conditions on tree growth reflects variations in wood anatomical features. No significant response to soil type was observed in saplings, thus demonstrating that the relationship between soil type and wood growth is mediated by tree age. These findings help to develop reliable reforestation strategies in tropical ecosystems characterized by different levels of soil fertility.

Analyses of Microstructure and Dynamic Deposition of Cell Wall Components in Xylem Provide Insights into Differences between Two Black Poplar Cultivars

The chemical composition of the cell wall varies between species and even within the same species, and impacts the properties of the cell wall. In this study, the dynamic chemical compositions of the xylem cell walls of two black poplar cultivars, Populus × euramericana ‘Zhonglin46’ and Populus × euramericana ‘Neva,’ were investigated in situ using stimulated Raman scattering microscopy (SRS). Meanwhile, the pectin structural features were examined using immunofluorescence methods. The results showed that Neva displayed faster thickening of the fiber cell walls than Zhonglin46 did, and it had a greater cell wall thickness in mature xylem. A faster deposition speed of lignin and cellulose during xylem maturation was revealed in Neva. Significantly higher lignin contents were found in the mature xylem of Neva compared with those of Zhonglin46, while no obvious differences in cellulose deposition in mature xylem were observed between the two cultivars. The patterns of pectin deposition during xylem maturation were similar in the two cultivars, but more pectin was found in the mature xylem of Neva than in that of Zhonglin46. The chemical deposition patterns account for the anatomical feature differences between the cultivars. These results provide valuable insights into the chemical deposition and anatomical differences between cultivars, and they might be helpful in understanding the wood growth processes and facilitating the utilization of different poplar cultivars.

Experimental study on the complementary inverse reconstruction of tree growth state data by radar detection and 3D raster scan

Three-dimensional modeling of the growth characteristics of living wood is a difficult problem. In tree growth characteristics of nondestructive testing of data, how to process the image of tree growth defect and how to reconstruct the three-dimensional model of tree growth is the key technology, so the use of radar signal detection feedback internal growth of the trunk, using 3D raster scan reverse image processing techniques reverse reconstruct the 3D shape data of standing timber, realize the radar wave nondestructive test of lumber and 3D scanning and grating surface more stitching way as complementary is the effective solution. In this study, the feedback data of radar wave detection of internal defects of trees and the feedback data of root growth condition of trees were analyzed, so as to complete the digital data collection of invisible internal growth condition of trees. In this study, 3D grating method was used to scan wood specimens for inverse surface fitting modeling, and then the surface model of tree specimens was reconstructed by splicing multi-point markers on the scanned point cloud data, and the multi-surface grouping fitting method was used to successfully reduce the splicing error. Experimental results are obtained by stocking the trunk of the growth of internal defects inspection information, analyzes the testing information after statistical data for the chart, the experimental results of 3D scanning the reverse reconstruction is to obtain the stocking complex 3D data in the form of external information, through the application of this technology, the effective of the radar wave nondestructive testing technology is obtained with 3D scanning grating reverse reconstruction technology application in tree growth data sampling method, this method can empty of wood rotting pathological monitoring, trees outside surface can be three-dimensional characteristics of surface reconstruction. This conclusion is the application of ray detection technology and pattern recognition technology in the field of wood growth monitoring.

Climate change during the deposition of the Aptian Santana Formation (Araripe Basin, Brazil): Preliminary data based on wood signatures

This paper presents preliminary results of paleoclimatic signatures of conifer woods during the deposition of the basal Crato and topmost Romualdo members of the Santana Formation within the Tropical Equatorial Hot Arid Belt (late Aptian, Araripe Basin, Brazil). Analysis was carried out using standard thin sections, and the anatomical details were studied in transmitted light. The wood growth pattern from the lowermost laminated lacustrine carbonate level of the Crato Member was characterized by the absence of true growth rings and the common presence of wood growth interruptions, and could be linked to a tropical, equable but erratically humid environment. In an interlayered fine-to-coarse sandstone level attributed to a fluvio-deltaic interval, the wood growth pattern was homogeneous, lacking true growth rings, with weakly delineated growth interruptions over long radial distances. In this level the growth pattern could be related with a transition to a more equable tropical climate during a relatively humid period. In contrast, the wood pattern from the carbonate succession of the uppermost Romualdo Member, interpreted as a lagoon area with marine influence, showed true growth rings with abrupt ring boundaries and rings of variable width, also including frequent growth interruptions. This pattern could be linked to a monsoonal-like climate, subjected to distinct cyclical conditions and periodical droughts during the growing season.

Regionwide temporal gradients of carbon allocation allow for shoot growth and latewood formation in boreal black spruce

AbstractAimIn boreal ecosystems, phenological events display seasonal patterns. These patterns allow for the development of tissues during the short time window available for growth in cold climates. Primary and secondary growth, two expensive processes for plants, are supposedly modulated in time to optimize allocation of carbon to bud and woody tissues. We aimed to assess the phenology of primary and secondary meristems, testing their relationship over the closed black spruce stands of the commercially exploited forest region in Quebec, Canada.LocationQuebec, Canada.Time period2002–2016.Major taxa studiedGymnospermae.MethodsWe combined weekly scaled field observations with Moderate Resolution Imaging Spectroradiometer (MODIS) time series of the normalized difference vegetation index (NDVI) to extract timings of photosynthesis and meristem growth in five black spruce [Picea mariana (Mill.) B.S.P.] stands located along a latitudinal gradient and to assess their relationship. We then tested empirical models based on geographical position and seasonal temperatures to predict wood phenology (i.e., the onset and ending of earlywood and latewood formation), and compared its spatial patterns with existing predictions of bud phenology for the same study area.ResultsPhotosynthesis started at the beginning of May, 3 weeks before bud reactivation and the onset of wood growth. Latewood formation started in mid‐July, after shoot elongation was completed. For wood phenology models, the residual standard error ranged from 1 week to 12 days. Growth dynamics spatialized across the boreal forest of Quebec varied with the transition between the subarctic and humid continental climate.Main conclusionsShoot elongation and latewood formation were temporally separated, providing evidence of a trade‐off in structural carbon allocation between primary and secondary growth in trees. Spatial patterns of wood phenology predicted for the black spruce polygons are consistent with spatial patterns of bud phenology, demonstrating synchronized temporal dynamics of meristems at the regional scale.

Comparison of community structures of Phoebe chekiangensis pure forests and heterogeneous mixed forests

Taking the 13 years pure artificial forest Phoebe chekiangensis and heterogeneous mixed forests in Tiantong mountain, Zhejiang Province as the research object, the characteristics of stand development, tree competition differentiation, tree height/breast diameter ratio and dominant wood growth were compared and analyzed from the perspective of ecology. The results show that compared with pure forests, the growth advantages of heterogeneous mixed-age forests were significant. Average breast diameter growth of stand increased 1.8%; the growth of single plant wood accumulation increased 7.4%. The relationship between tree height and diameter showed that the high growth of Phoebe chekiangensis individuals in the heterogeneous mixed forest was significantly promoted, and the high growth of the tree was 8.4% higher than that of pure forest. 1–5 grade wood scale sizes Phoebe chekiangensis in heterogeneous mixed forests and pure forests are ranked grade 3 (43.7%) > grade 2 (26.5%) > grade 4 (15.7%) > grade 1 (12.9%) > grade 5 (1.2%); grade 3 (34.7%) > level 2 (25.6%) > level 4 (20.0%) > level 1 (18.2%) > level 5 (1.2%); the straight-diameter structure shows a normal distribution, and the degree of differentiation of pure forests is greater than that of heterogeneous forests. The dominant trees of Phoebe chekiangensis pure forest and heterogeneous forest accounted for 18.2% and 12.9% of the total number of plants respectively, providing a reserve of 51.1% and 35.4% respectively, reflecting the contribution of dominant trees caused by the self-thinning effect.

Bioinspired thermochromic transparent hydrogel wood with advanced optical regulation abilities and mechanical properties for windows

The huge heat loss/gain through windows is the cause of great energy consumption in buildings. In addition, the traditional fabrication method for glass causes many environmental problems. Recently, transparent wood has emerged as a promising alternative to traditional glass because of its high transmittance, strong mechanical properties, excellent thermal insulation ability and sustainability. In this study, inspired by jellyfish, a thermochromic transparent hydrogel wood that can smartly regulate solar irradiation is proposed as a smart window material by impregnating Poly(N-isopropylacrylamide)-polyacrylamide hydrogel into delignified wood. The novel thermochromic transparent hydrogel wood inherits the excellent thermochromic properties of PNIPAM and strong mechanical properties of wood, showing advanced optical regulation ability (i.e. Tlum = 82.7% and 39.8% at the cold and hot states &ΔTsol = 38.1%), low transition temperature (i.e. Tc = 22.9 °C), mechanically robust (i.e. σ = 11.6 MPa along the axial direction) and low thermal conductivity (i.e. K = 0.37 W m−1 K−1 along the perpendicular direction of the wood growth). A field test conducted in October in Hong Kong shows that thermochromic transparent hydrogel wood can reduce the indoor air temperature by 4.3 °C. Furthermore, a computational simulation for an office building proves that 2.6–10.2% energy could be saved by thermochromic transparent hydrogel wood in four different climate-zone cities. Besides, thanks to the flexibility, thermochromic transparent hydrogel wood can be easily fitted on existing windows, demonstrating the great potential for use in energy-efficient buildings.

3D Reticulated Actuator Inspired by Plant Up-Righting Movement Through a Cortical Fiber Network.

Since most plant movements take place through an interplay of elastic deformation and strengthening tissues, they are thus ideal concept generators for biomimetic hingeless actuators. In the framework of a biomimetic biology push process, we present the transfer of the functional movement principles of hollow tubular geometries that are surrounded by a net-like structure. Our plant models are the recent genera Ochroma (balsa) and Carica (papaya) as well as the fossil seed fern Lyginopteris oldhamia, which hold a net of macroscopic fiber structures enveloping the whole trunk. Asymmetries in these fiber nets, which are specifically caused by asymmetric growth of the secondary wood, enable the up-righting of inclined Ochroma and Carica stems. In a tubular net-like structure, the fiber angles play a crucial role in stress–strain relationships. When braided tubes are subjected to internal pressure, they become shorter and thicker if the fiber angle is greater than 54.7°. However, if the fiber angle is less than 54.7°, they become longer and thinner. In this article, we use straightforward functional demonstrators to show how insights into functional principles from living nature can be transferred into plant-inspired actuators with linear or asymmetric deformation.

Self-Densified Optically Transparent VO2 Thermochromic Wood Film for Smart Windows.

Optically transparent wood has emerged as a promising glazing material. Thanks to the high optical transmittance, strong mechanical properties, and excellent thermal insulation capability of transparent wood, it offers a potential alternative to glass for window applications. Recently, thermo-, electro-, and photochromic transparent woods that dynamically modulate light transmittance have been investigated to improve building energy efficiency. However, it remains challenging to widely replace windows with transparent wood because of its poor weather resistance. In this study, an environment-friendly thermochromic transparent wood film (TTWF) with thermal switching of transmittance is proposed and demonstrated. To achieve thermochromism, the bleached wood is impregnated with the vanadium dioxide (VO2)/polyvinyl alcohol composite. Due to the self-densification of cellulose microfibrils during the evaporation of solvents, the transparent wood is in the form of thin films, which can be attached on the inner face of a window to protect it from severe weather conditions, making the installation convenient and low-cost. Furthermore, the surface of VO2-TTWF is modified by octadecyltrichlorosilane to enhance the waterproof ability and achieve self-cleaning and antidust functions. The proposed VO2-TTWF shows great potential for application in energy-efficient buildings using sustainable materials with advanced optical properties (i.e., Tlum = 50.5%, ΔTsol = 3.4%, and haze = 70%) that are mechanically robust (i.e., σ = 130.6 MPa along the wood growth direction), have low-thermal conductivity (i.e., K = 0.29 W m-1 K-1 along the perpendicular direction to the wood fibers), and demonstrate hydrophobic self-cleaning and antidust functions (i.e., contact angle: 121.9°). An experiment, using a model house, showed that the VO2-TTWF attached on the inner face of the window could significantly reduce the indoor air temperature by 33.9 °C compared with a bare glass panel, proving that VO2-TTWF has potential to be applied as a new-generation energy-efficient material for smart windows.

Crown defoliation decreases reproduction and wood growth in a marginal European beech population.

Abiotic and biotic stresses related to climate change have been associated with increased crown defoliation, decreased growth and a higher risk of mortality in many forest tree species, but the impact of stresses on tree reproduction and forest regeneration remains understudied. At the dry, warm margin of species distributions, flowering, pollination and seed maturation are expected to be affected by drought, late frost and other stresses, eventually resulting in reproduction failure. Moreover, inter-individual variation in reproductive performance versus other performance traits (growth, survival) could have important consequences for population dynamics. This study investigated the relationships among individual crown defoliation, growth and reproduction in a drought-prone population of European beech, Fagus sylvatica. We used a spatially explicit mating model and marker-based parentage analyses to estimate effective female and male fecundities of 432 reproductive trees, which were also monitored for basal area increment and crown defoliation over 9 years. Female and male fecundities varied markedly between individuals, more than did growth. Both female fecundity and growth decreased with increasing crown defoliation and competition, and increased with size. Moreover, the negative effect of defoliation on female fecundity was size-dependent, with a slower decline in female fecundity with increasing defoliation for the large individuals. Finally, a trade-off between growth and female fecundity was observed in response to defoliation: some large trees maintained significant female fecundity at the expense of reduced growth in response to defoliation, while some other defoliated trees maintained high growth at the expense of reduced female fecundity. Our results suggest that, while decreasing their growth, some large defoliated trees still contribute to reproduction through seed production and pollination. This non-coordinated decline of growth and fecundity at individual level in response to stress may compromise the evolution of stress-resistance traits at population level, and increase forest tree vulnerability.

Hafting with a Living Tree: A Historical Review of the Alleged Practice of Growth-Assisted Hafting

ABSTRACT Despite facing the challenges of preservation and rarity of evidence in the archaeological record, hafting methods are a research pursuit of archaeologists seeking to explain the construction of weapons and tools. Various works have included references to a unique method of hafting, referred to in this article as growth-assisted hafting, which involved inserting a stone into a living tree branch and waiting for wood growth to encase the inclusion before harvesting and constructing the knife, club or axe. Such a method would lack toolmarks and exhibit some evidence in wood grain patterns and possible abnormal fiber build-up of continued tree growth around the inclusion. This paper is a historical review of the alleged practice based on accounts from around the world and how the practice has re-appeared in the modern primitive skills subculture.

Wood anatomy, fire wounds and dendrochronological potential of Prosopis pugionata Burkart (Fabaceae) in arid Argentine Chaco

Abstract Prosopis pugionata (Fabaceae) is a halophyte tree species that grows exclusively in Argentina’s arid environments, whose woodlands are mainly affected by fires and overgrazing. Here, we describe the wood anatomy and fire wounds of P. pugionata and their relationship with plant size and bark thickness. Besides, we attempt to determine the potential of P. pugionata for dendrochronological studies in order to date fire events throughout time. We tested the hypothesis that P. pugionataforms datable fire wounds, allowing its use for dendrochronological studies. The study area is located in the arid Argentine Chaco region. Seventeen individuals, varying from 15 to 65 years of age, were randomly sampled and bole disks were taken at 0.3, 1.3 and 2.3 m high. P. pugionatais a diffuse and semi-ring-porous hardwood species with growth rings delimited by marginal parenchyma bands. The bark is longitudinally fissured, with an average thickness of 0.19 cm, and a scarce increase with age. Seventy-seven percent of the samples showed fire wounds (). We identified fire scars (70%) and marks (30%), and differentiated them by wood growth interruption in the former. Sixty-one percent of fire wounds affected less than 20% of the cambial perimeter and there were no significant effects of age, bole diameter, bole height and bark thickness on the cambial damage percentage. After cross-dating, P. pugionata showed a mean correlation value between series of 0.5, which represents an accurate potential for dendrochronological studies. Twenty wildfires were dated from 1943 to 2007 in the study area with a fire frequency of 0.40 fires/year and a mean fire interval of 2.5 years. Wildfires frequency increased from 1980 to 0.48 fires/year and a mean fire interval of 2 years. Our results indicate that P. pugionata has the potential to date fires, considering its potential for dendrochronological studies, its ability to survive recurrent fires and forms identifiable wound scars in the wood.

Paleoclimatic inferences based on wood growth interruptions in Late Triassic flood deposits from the southernmost Brazilian Gondwana

The goals of this study were to establish patterns in a silicified wood assemblage to depict the evolution patterns of the Triassic paleoclimate in southern Brazilian Gondwana during an interval of global arid to semi-arid climatic context, and the taphonomic process that led to the preservation of the so-called “Petrified Forest”, which is preserved in the central area of the state of Rio Grande do Sul. Analyses were developed with an assemblage of 13 permineralized conifer wood, using standard thin sections, whose anatomical details were studied in transmitted light. Ground-Penetrating Radar was used to obtain information about the depositional characteristics of the site. Main results are: true growth rings are absent in all samples, and the boundaries of the interruption zones are marked by an abrupt decline in cell diameter, but they are not accompanied by a reduction of cell wall thickness. The subsequent reversion to normal tracheid diameter is also abrupt, revealing the return of the previous growing conditions. Ground-penetrating Radar analyses confirmed that the Mata Sequence deposits correspond to a river. The identification of growth interruption zones in a Late Triassic wood assemblage in southernmost Brazilian Gondwana (Paleobotanic Garden of the city of Mata, RS) indicates the presence of tropical, temporarily dry climate conditions, characterized by irregular, short-term environmental disturbances to growth. The taphonomic process was related to a river-channel infilling depositional process, under the influence of high-energy flood events that dragged and buried the trees. Keywords: Wood growth patterns, Mata sequence, gymnosperms, Triassic climate, petrified forest.

Growth–density relationship in mixed stands – Results from long-term experimental plots

Forest management mainly controls wood growth through the regulation of stand density. Knowledge of the growth–density relationship is based on numerous studies in pure stands. Currently, in times of more climate plasticity and more nature-oriented forests, silviculture with mixed stands is demanded of forest policy. It is well known that the competition mechanisms in mixed stands are different to those of pure stands. Hence, the question arises for forest managers whether the regulation of density must be different, too.In an attempt to answer this question, we investigated 481 stand surveys from 124 long-term experimental plots of European beech stands, mixed with conifers and also broadleaf trees. With generalized additive models, we estimated the influence of the density on stand volume growth and how it changed with stand development and shade tolerance of the admixed species. The density of the mixed stands was given on a relative scale. 100% density took into account the maximum species-specific density plus a mixed stand specific addition.We found that mixed stands have a constant growth level in the medium- to high-density phase (70–100%). Although we have tried to take into account the higher density in mixed stands, 10% of the stands outperformed the 100% benchmark and exhibited a growth gain in this over-dense phase (>100%). Finally, the growth-density response resembles a cubic function with a saddle or optimum between medium- to high-density phase and an increase of growth in the low-density and the over-density phase. The inclusion of stand development led to the oblation of the growth–density response in younger ages. The admixture of shade-intolerant species with beech caused a more intensified cubic course of the relationship.Finally, we could show that a short-term decrease of the density also has an effect on growth. In terms of growth, weak thinnings are better than severe thinnings. Thinnings from above have a significant positive effect on growth, especially for longer observation periods of up to 10 years.We concluded that mixed stands need an adapted thinning compared to pure stands. Regular, weak thinnings from above with a very high stand density enables maximum volume growth gains in European beech mixed stands. We could show that the growth-density relationship is conceptually different to pure stands, because mixing effect causes density section above 100%. However, the study emphasizes the need for a systematic experimental setup for a better understanding of intraspecific interactions at different densities.

Оценка влияния сжигания попутного газа на радиальный прирост Pinus sylvestris (Озёрное месторождение нефти, Пермский край, Россия)

The paper discusses the question of influence of associated gas flaring on radial growth of Pinus sylvestris. The studied area is Ozernoye oil field of Krasnovishersky district of Perm region (Russia). The main research method is dendrochronological analysis. The wood cores of Pinus sylvestris were selected in the summer of 2020 using a Pressler increment borer according to the standard methodology. Cores were taken from two plots. The main plot is 100 m from the associated gas flaring torch and background plot is 11 km from the torch. The calculation and measurement of the width of the radial growth of wood were made on the machine for measuring tree rings – LINTAB 6. Numerical parameters of wood growth obtained for both plots. The average value growth of wood at the main plot is 1.426 mm/year; at the background plot – 1.808 mm/year. The relative decrease of average growth of wood over 20 years before and after the start of associated gas flaring at the main plot 1.45 times higher than at the background plot. The radial growth decreases systematically at both plots for 20 years since the beginning of associated gas flaring. But the rates of decrease are 1.52–1.67 times higher near the torch. The trend for recovery, as well as increase in the growth values, 10-20 years after the start of associated gas flaring, was not revealed. Therefore, the explicit negative impact of associated gas combustion on the radial growth of wood in nearest forest were noted. Maximum growth rates at the main plot were noted for trees ages 0-55 years. It is not supporting the conclusions of some researches [7,37] that Pinus sylvestris has the most intense growth during 30-35 years old. Revealed [37] high levels of chemical and dust atmospheric contamination, reducing growth of wood, most likely cannot be achieved by the associated gas flaring by the single torch. Positive (fertilizing) influence of Ca, K, Na, Mg, Mn [29,30] compounds emissions is not marked as well. We guess that thermal – is the main negative factor for the plot near associated gas flaring. Our research could be continued to the studying of the influence of spatial, climatic aspects, volume and intensity of gas flaring process on the state of forest stand.

Timing of spring xylogenesis in temperate deciduous tree species relates to tree growth characteristics and previous autumn phenology.

We explored the timing of spring xylogenesis and its potential drivers in homogeneous mature forest stands in a temperate European region. Three species with contrasting leaf development dynamics and wood anatomy were studied: European beech, silver birch and pedunculate oak. Detailed phenological observations of xylogenesis and leaf phenology were performed from summer 2017 until spring 2018. Cambium reactivation (CR) occurred before the buds of oak and birch were swollen, whereas these two phenological phases were concurrent for beech. On the other hand, initial earlywood vessels were fully differentiated (FDIEV) after leaf unfolding for all three species. Timing of CR was correlated to average ring-width of the last 10years (2008-17), tree diameter and, partially, with tree age. In addition, the timing of FDIEV was correlated to tree age and previous year's autumn phenology, i.e., timing of wood growth cessation and onset of leaf senescence. Multivariate models could explain up to 68% of the variability of CR and 55% of the variability of FDIEV. In addition to the 'species' factor, the variability could be explained by ca 30% by tree characteristics and previous year's autumn phenology for both CR and FDIEV. These findings are important to better identify which factors (other than environment) can be driving the onset of the growing season, and highlight the influence of tree growth characteristics and previous year's phenology on spring wood phenology, wood formation and, potentially, forest production.

Trace metals as indicators of tree rooting in bituminous soils

AbstractIn some reclamation practices, following bitumen mining in the Canadian Boreal forest, overburden containing low concentrations of hydrocarbons (<8% of bulk soil volume) is buried under suitable soils. Residual hydrocarbons may influence the growth of trees used in afforestation of reclaimed sites, thus determining whether roots interact with buried bitumen is a key to predicting reclamation success. As the organic fraction of bitumen is enriched in vanadium, nickel, molybdenum, and rhenium, dendrochemistry may be a method to determine whether tree roots are interacting with bitumen without disturbing soils. We analyzed trace concentrations of these metals in soil, soil pore water, and tree cores of Pinus banksiana growing on natural bitumen deposits and sites free of bitumen. If roots are present within bitumen and passively uptake trace metals during water transport and wood growth, metals enriched in bitumen should be present in higher concentrations in the woody tissue of trees growing in bituminous soils compared to trees growing in bitumen‐free soils. Concentrations of nickel in trees growing on shallow bitumen deposits were approximately 3× higher than those growing in bitumen‐free soils. The concentration of vanadium (1.33 μg kg−1 in younger wood and 3.21 μg kg−1 in older wood) was also elevated in trees on bituminous sites, though not significantly. Molybdenum concentrations decreased by ~25% in trees growing on bituminous sites, likely an outcome of soil pH. This research supports the use of dendrochemistry to investigate, and potentially monitor, tree rooting at depth in substrates with signature metals.

Direct response of tree growth to soil water and its implications for terrestrial carbon cycle modelling

Wood growth constitutes the main process for long-term atmospheric carbon sequestration in vegetation. However, our understanding of the process of wood growth and its response to environmental drivers is limited. Current dynamic global vegetation models (DGVMs) are mainly photosynthesis-driven and thus do not explicitly include a direct environmental effect on tree growth. However, physiological evidence suggests that, to realistically model vegetation carbon allocation under increased climatic stressors, it is crucial to treat growth responses independently from photosynthesis. A plausible growth response function suitable for global simulations in DGVMs has been lacking. Here, we present the first soil water-growth response function and parameter range for deciduous and evergreen conifers. The response curve was calibrated against European larch and Norway spruce in a dry temperate forest in the Swiss Alps. We present a new data-driven approach based on a combination of tree ring width (TRW) records, growing season length and simulated subdaily soil hydrology to parameterize ring width increment simulations. We found that a simple linear response function, with an intercept at zero moisture stress, used in growth simulations reproduced 62.3% and 59.4% of observed TRW variability for larch and spruce respectively and, importantly, the response function slope was much steeper than literature values for soil moisture effects on photosynthesis and stomatal conductance. Specifically, we found stem growth stops at soil moisture potentials of -0.47MPa for larch and -0.66MPa for spruce, whereas photosynthesis in trees continues down to -1.2MPa or lower, depending on species and measurement method. These results are strong evidence that the response functions of source and sink processes are indeed very different in trees, and need to be considered separately to correctly assess vegetation responses to environmental change. The results provide a parameterization for the explicit representation of growth responses to soil water in vegetation models.

Wood properties and transcriptional responses of poplar hybrids in mixed cropping with the nitrogen-fixing species Robinia pseudoacacia.

Cultivation of fast-growing tree species is often confined to marginal land. Mixed cropping with Robinia pseudoacacia, a legume tree species that forms a symbiosis with N2-fixing bacteria, has been proposed to be a measure to improve soil fertility and to achieve beneficial effects on the cocultivated tree species. The goal of our study was to examine the influence of a Robinia mixture on wood chemistry, anatomy and gene expression in poplar. We hypothesized that annual wood growth is stimulated in species mixtures due to the positive effects of Robinia on nitrogen availability and complementary resource use. Alternatively, we hypothesized that competition, especially for water, has negative effects on the wood growth of poplar. We used two commercial biomass clones, Hybride 275 (H275, Populus trichocarpa×Populus maximowiczii) and Max1 (Populus nigra×P. maximowiczii), which were planted at two locations with contrasting soil fertility in monoculture or mixed plots with Robinia to investigate the annual wood increment, wood nitrogen and δ13C, wood anatomy (length, cell wall thickness, lumina and frequencies of fibers and vessels) and transcriptional profiles in the developing xylem of 4-year-old stems. In a mixture with Robinia, the annual stem increment was reduced, nitrogen in wood was enhanced, δ13C in wood was decreased, vessel and fiber frequencies were increased and fiber lengths and fiber lumina were decreased. Transcriptional profiles showed stronger differences between the genotypes and sites than between mono and mixed cultivation. The transcriptional abundances of only one gene (the putative nitrate transporter, NRT1.2) and one gene ontology term ('immune system process') were significantly enriched in wood-forming tissues in response to the mixture, irrespective of the poplar genotype and growth location. Weighted gene coexpression network analyses extracted gene modules that linked wood nitrogen mainly to vessel traits and wood δ13C with fiber traits. Collectively, molecular and anatomical changes in poplar wood suggest beneficial effects on the water and N supply in response to the mixture with Robinia. These alterations may render poplars less drought-susceptible. However, these benefits are accompanied by a reduced wood increment, emphasizing that other critical factors, presumably light competition or allelopathic effects, overrule a potential growth stimulation.

Unique 3D interpenetrating capillary network of wood veneer for highly efficient cross flow filtration

Natural wood is mainly comprised of numerous long, partially aligned channels which are connected by micropores (such as ray cells, pits) providing high-efficiency nutrient transportation corridor. Here, thin wood veneer (the thickness of 400 μm) was used to design catalytic membrane for water treatment with reversed-tree transport pathways. As filtering direction is nearly perpendicular to wood growth direction, wood veneer possesses abundant sinuous water channels based on partially aligned and interconnected cell lumens which provide long enough micro reaction and suitable water transfer pathways in a greatly reduced thickness. Meanwhile due to a small rotary cutting angle, large number of incisions of vessels and fibers were formed ensuring large inlet area for fluid transport. And mussel-inspired polydopamine (PDA) was used to modify the surface of wood pores with highly active functional groups. Then, Pd nanoparticles could be in situ grown and immobilized onto wood channels via these groups (Pd/PDA/wood veneer). On account of the unique 3D interpenetrating capillary network structure, Pd/PDA/wood veneer shows a highly efficient water treatment for methylene blue (MB) solution. The flux of Pd/PDA/wood veneer can reach 3462 L/(m2h) with high MB removal efficiency (> 95%), meanwhile it shows good mechanical strength and flexibility. The designed thin wood veneer with unique structure exhibits promising results for practical wastewater treatment and even wider applications such as solar-thermal conversion, microreactor design.