Key message
Decreasing stand density increases resistance, resilience, and recovery of
Quercus petraea
trees to severe drought (2003), particularly on dry sites, and the effect was independent of ...tree social status.
Context
Controlling competition is an advocated strategy to modulate the response of trees to predicted changes in climate.
Aims
We investigated the effects of stand density (low, medium, high; relative density index 0.20, 0.53, 1.04), social status (dominant, codominant, suppressed), and water balance (dry, mesic, wet; summer water balance − 182, − 126, − 96 mm) on the climate-growth relationships (1997–2012) and resistance (Rt), resilience (Rs), and recovery (Rc) following the 2003 drought.
Methods
Basal area increments were collected by coring (269 trees) in young stands (28 ± 7.5 years in 2012) of sessile oak (
Quercus petraea
) in a French permanent network of silvicultural plots.
Results
We showed that the climate-growth relationships depend on average site-level water balance with trees highly dependent on spring and summer droughts on dry and mesic sites and not at all on wet sites. Neither stand density nor social status modulated mean response to climate. Decreasing stand density increased Rt, Rs, and Rc particularly on dry sites. The effect was independent of tree social position within the stand.
Conclusion
Reducing stand density mitigates more the effect of extreme drought events on drier sites than on wet sites.
Key message
Xylem vulnerability to drought-induced embolism did not differ between stems and petioles of four woody species (
Betula pendula
,
Liriodendron tulipifera
,
Populus tremula
and
Olea ...europaea
). Our results, together with data compiled from published literature, indicate that hydraulic segmentation during drought stress is not consistently driven by difference in vulnerability to embolism between stem and terminal organs.
Context
Hydraulic failure and disconnection of distal organs during protracted drought stress is thought to protect large branches or trunks by reducing water loss and restricting the spread of embolism. Hydraulic segmentation and preferential sacrifice of distal organs such as leaves can be driven by two mechanisms: more negative water potentials at the terminal section of the hydraulic pathway and/or by higher vulnerability to xylem embolism of distal organs. Although vulnerability segmentation has been reported in the literature, the generality of this phenomenon is unclear, in part due to the methodological limitations related to direct measurement of xylem vulnerability to embolism in intact plants.
Aims
The objective of this study was to evaluate vulnerability segmentation between petioles and stems using non-invasive micro computed tomography (microCT).
Methods
Vulnerability to embolism was measured in leaf petioles and subtending stems of four woody species (
Betula pendula
R.,
Liriodendron tulipifera
L.,
Populus tremula
L. and
Olea europaea
L.) with contrasting drought tolerances. In addition, previously published vulnerability data for petioles and stems were compiled from the literature to investigate the commonality of hydraulic segmentation across a wide range of woody species, with the vulnerability curve methodology distinguished.
Results
Using non-invasive imaging on intact plants, we found no evidence of hydraulic segmentation between petioles and stems of four angiosperm tree species, regardless of mechanism. Moreover, the literature dataset indicated that little or no difference in vulnerability to embolism is present between petioles and stems when vulnerability curves were constructed using methods specifically measuring the dynamics of xylem tissue during dehydration (e.g. optical visualization, MicroCT).
Conclusion
Our results suggest that vulnerability segmentation between stems and distal organs (petioles and leaves) is limited when only xylem tissue is considered. Large differences in vulnerability between stems and leaves are likely to be driven by extra-xylary components, rather than xylem embolism.
The aging process, although not mandatory in the production of
cachaça
, adds sensory complexity to the beverage. During the aging process, several physicochemical reactions occur between the wood ...and the distillate, such as hydrolysis, oxidation, polymerization, and esterification. The phenolic compounds related to maturation, extracted from the wood, directly interfere in the chemical and sensory composition of the distillate. However, knowledge of wood composition is not enough to determine the sensory profile of
cachaça
, since this also depends on numerous factors such as the origin of the wood, wood species, barrel manufacturing, number of times the barrel was used, aging time, and composition of the beverage. This research explores, quantitatively and qualitatively, the influence of these factors on the extraction of phenolic compounds derived from lignin in
cachaça
aged up to 144 months in oak barrels of different origins using high-performance liquid chromatography. The content of phenolic compounds increased at an accelerated rate in the first years of aging. Nonetheless, the wood species and the number of times the barrels were used exhibited great influence on the evolution of aging, regardless of the aging time. Regarding the extraction of maturation indicators, each year of aging in new barrels corresponded to approximately 5 years of aging in extensively used barrels.
There is increasing interests in the significant improvement of impregnation amount and efficiency in wood by the pre-treatment of compression. Thus, attention is paid to pre-treatment by compression ...for harder impregnation with resin because of the large viscosity and relatively large molecular weight of the resin. Low-molecular-weight phenol formaldehyde (PF) resin of solid content of 10–48% were impregnated by pre-treatment of compression at a compression ratio of 60% and 40% for poplar and Chinese fir, respectively, to systematically study the effects of solid content on the impregnation amount, weight gain percentage (WGP). In addition, the distribution of resin in wood was analyzed by profile density and was observed by confocal laser scanning microscope (CLSM), and the change of crystallinity index (C
r
I) of resin-impregnated wood was investigated by X-ray diffractometer. The results showed: (1) compared with immersion impregnation without compression, the impregnation by pre-treatment of compression, was much larger in amount and higher in efficiency for resins in all solid contents. In a solid content range of 10–48% and at a molecular weight of about 517, there was no significant difference of impregnation amount by compression among the resins at different solid content. (2) The WGP of poplar and Chinese fir increased with the increase of resin solid content. When the resin solid content increased from 10 to 48%, the WGP increased from 8.9 to 44.2% and from 5.2 to 24.9% for poplar and Chinese fir, respectively. (3) Resin is mainly distributed in vessels and tracheids despite a few being distributed in the fiber near the longitudinal end of the poplar specimens. With the increase of solid content, the resin distribution gradually changed from diffusing on the wall to depositing in the vessel or tracheid, while the resin distribution evenness along the longitudinal direction decreased. There was more resin deposited near the longitudinal end of Chinese fir at deeper depth than that of poplar. (4) The resin can be impregnated into the amorphous area of wood without causing any change in the crystallization area. The C
r
I decreases with the increase of resin solid content. After all, it is concluded that the pre-treatment by compression for wood impregnation with low-molecular-weight PF resin is effective for all the solid contents for both poplar and Chinese fir. The WGP increased with the increase of resin solid content, despite the decrease of evenness of resin distribution at high solid content.
In this paper, a set of improvements made in drill wear recognition algorithm obtained during previous work is presented. Images of the drilled holes made on melamine faced particleboard were used as ...its input values. During the presented experiments, three classes were recognized: green, yellow and red, which directly correspond to a tool that is in good shape, shape that needs to be confirmed by an operator, and which should be immediately replaced, since its further use in production process can result in losses due to low product quality. During the experiments, and as a direct result of a dialog with a manufacturer it was noted that while overall accuracy is important, it is far more crucial that the used algorithm can properly distinguish red and green classes and make no (or as little as possible) misclassifications between them. The proposed algorithm is based on an ensemble of possibly diverse models, which performed best under the above conditions. The model has relatively high overall accuracy, with close to none misclassifications between indicated classes. Final classification accuracy reached 80.49% for biggest used window, while making only 7 critical errors (misclassifications between red and green classes).
This study investigated the effects of pH, salinity, biomass concentration, and algal organic matter (AOM) on the efficiency of four commercial cationic flocculants. The tannin-based biopolymers ...Tanfloc SG and SL and the polyacrylamide polymers Flopam FO 4800 SH and FO 4990 SH were tested for flocculation of two microalgae models, the freshwater
Chlorella vulgaris
and the marine
Nannochloropsis oculata
. Both biomass concentration and AOM presence affected all polymers evaluated, whereas salinity and pH affected only Flopam and Tanfloc, respectively. A restabilization effect due to overdosing was only observed for Flopam polymers and increasing Tanfloc dose resulted in improved efficiency. Flopam polymers showed a significant decrease in the maximum quantum yield of photosystem II as function of polymer dose for
Chlorella
, which supported the need for toxicological studies to assess the potential toxicity of Flopam. In overall, Tanfloc was not affected by salinity nor presented potential toxicity therefore being recommended for the flocculation of both freshwater and marine species.
•
Key message
Decomposition of forest herb species litter was not always completed in less than a year and was not always faster than decomposition of tree leaf litter in an oak-hornbeam forest in ...Western Poland. Litter decomposition of herbaceous plants is connected with their life strategy and functional traits of their leaves.
•
Context
Forest understories are frequently ignored in ecological research on decomposition, although they play an important role in biomass and nutrient cycling in forest ecosystems.
•
Aims
We hypothesized that the decomposition process of herbaceous species was completed in less than a year, as opposed to tree leaf litter. The second aim of our study was to determine if life strategy affects the rate of litter decomposition.
•
Methods
We performed the decomposition experiment in the oak-hornbeam forest in Czmoń (Western Poland) using the litter bag method to determine decay constants (
k
) for all species studied. The influence of species identity, functional group, and functional traits of leaves and other effects on the decomposition process was assessed.
•
Results
The decomposition process was significantly dependent on the functional group of plants, time of exposure in the field, species identity, and precipitation. We found a significant correlation between leaf traits and decay rates of the species studied.
•
Conclusion
Litter decomposition of herbaceous plants is connected with their life strategy and functional traits of their leaves in an oak-hornbeam forests.
Key message
The history of the relationship between plant growth and water consumption is retraced by following the progression of scientific thought through the centuries: from a purely ...philosophical question, to conceptual and methodological developments, towards a research interest in plant functioning and the interaction with the environment.
Context
The relationship between plant growth and water consumption has for a long time occupied the minds of philosophers and natural scientists. The ratio between biomass accumulation and water consumption is known as water use efficiency and is widely relevant today in fields as diverse as plant improvement, forest ecology and climate change. Defined at scales varying from single leaf physiology to whole plants, it shows how botanical investigations changed through time, generally in tandem with developing disciplines and improving methods. The history started as a purely philosophical question by Greek philosophers of how plants grow, progressed through thought and actual experiments, towards an interest in the functioning of plants and the relationship to the environment.
Aims
This article retraces this history by following the progression of scientific questions posed through the centuries, and presents not only the main methodological and conceptual developments on biomass growth and transpiration but also the development of the carbon isotopic method of estimation. The history of research on photosynthesis is only touched briefly, but the development of research on transpiration and stomatal conductance is presented with more detail.
Conclusion
Research on water use efficiency, following a path from the whole plant to leaf-level functioning, was strongly involved in the historical development of the discipline of plant ecophysiology and is still a very active research field across nearly all levels of botanical research.
A novel X-ray scanner system to identify the positions of knots in logs is described. The scanner has a simple, low-cost design that is suitable for use in medium and smaller sawmills. It makes X-ray ...measurements in an oblique direction as the log moves longitudinally past the X-ray source and line-detector. This unconventional oblique measurement direction creates a more side-on view that better reveals the spatial arrangement of the knots within the log. This view, when combined with the knowledge that all knots start from along the pith and radiate outwards gives sufficient information to identify knot orientations in space. Experimental oblique X-ray measurements on a sample log are described, followed by the processing and analysis of the measured radiographs, and a comparison of the results with independent measurements of knot locations. With the knot identification algorithms developed, knot axial position could be identified within 11 mm, and knot circumferential orientation with a root mean square (rms) error of 7.9°–11.6° when using a single view X-ray scanner, or 5.6°–7.7° when using a dual view scanner.
Mechanical properties of wood–plastic composites are influenced by a particle size and surface morphology of wood flour. Generally various sizes of wood flour are produced from single solid wood even ...if the single process is used. If the different particle size of wood flour is produced from different wood tissue such as earlywood (EW) and latewood (LW), not only particle size but also density and chemical composition of wood flour might influence the mechanical property of final products. This study aims to investigate the relationship between particle size and their origin; EW and LW. EW and LW were separately milled to produce the EW and LW flour by dry and wet milling. Hyperspectral images ranging 400–1000 nm for each wood flour were used as training data. Discriminant model of EW and LW flour developed by PLS-DA showed over 0.77 of accuracy. Then the EW and LW were dry and wet milled together and screened by three different sieve openings to obtain different particle size wood flour. Discriminant model was applied for the hyperspectral images of each size of wood flour to estimate the EW and LW ratio. The result showed that increasing sieve opening resulted in the increasing ratio of LW for dry milled wood flours. The results suggest that the EW was easily pulverized than LW.
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