Toward improved understanding of the cell-wall density and porosity of wood determined by gas pycnometry

The main objective of this study was to evaluate the effect of sample preparation on cell-wall density and porosity using gas pycnometry. Native and thermally modified twin samples of Norway spruce (Picea abies (L.) Karst.), sycamore maple (Acer pseudoplatanus L.), and European ash (Fraxinus excelsior L.) were analyzed. The samples differed in terms of shape, geometry, and climatic state. On the one hand, the samples were oven dry as usual and, on the other hand, conditioned at 22 °C and 95 % relative humidity. Furthermore, the samples were processed using solvent exchange drying. In addition to helium, nitrogen was used as a displacement gas. The tests show i.a. how this can lead to misinterpretation of the cell-wall density or porosity of wood determined by gas pycnometry. The results show that native spruce has a lower cell-wall density and higher porosity compared with native maple and ash. Due to thermal modification, the cell-wall densities are decreased. The investigations show that the determined cell-wall density and porosity of the wood are strongly dependent on the sample geometry and climatic state. The cell-wall densities of all investigated wood species in the conditioned state at 22 °C and 95 % relative humidity are significantly higher compared with the oven-dry cell-wall densities.     

Spatial coexistence of American beech and sugar maple regeneration in post-harvest northern hardwood forests

Context

Fine scale regeneration patterns of coexistent species are influenced by regeneration mechanisms and microsite requirements. Spatial patterns may be either disjunct or overlapping, which will determine competitive effects and microsite dominance, and future forest composition.

Aims

Using American beech (Fagus grandifolia Ehrh.) and sugar maple (Acer saccharum Marshall) as an example, three hypotheses were tested: (1) random beech spatial patterns, (2) clumped spatial patterns of small sugar maple seedlings, and (3) disjunct beech and sugar maple patterns.

Methods

Individual stems were sampled in a contiguous grid of 1-m² quadrats across a 576-m² area at three sites. Densities were separated into three height classes (≤30 cm, 30–90 cm, and?>?90 cm, ≤4 cm diameter at breast height). Spatial statistics and regression were used to analyze spatial patterns and correlations.

Results

Beech and seedling sugar maple patterns were patchy, rejecting the first and not rejecting the second hypotheses. Hypothesis three was rejected because patches of the two species overlapped with advance regeneration beech overtopping sugar maple.

Conclusion

Patchy patterns of advance regeneration beech and post-harvest sugar maple establishment suggest spatiotemporal niche partitioning. Beech had a competitive height advantage following harvest, but sugar maple still occurred in beech-free patches and beneath overtopping beech at a fine scale. Self-replacing beech patterns will ensure the species will continue dominance unless a selective chemical or manual treatment is applied that removes beech and releases sugar maple.     

Analysis of the pore-size distribution and fiber saturation point of native and thermally modified wood using differential scanning calorimetry

The aim of this paper was to investigate pore-size distributions in the nano-diameter range of wood and their alteration due to thermal modification of wood using thermoporosimetry, and to find out what consequences can be derived regarding the biological durability. Thermoporosimetry is a technique that is based on the measurement using differential scanning calorimetry (DSC). The method is based on the fact that frozen water contained within small pores is at elevated pressure and therefore has a depressed melting temperature as a function of the appropriate pore diameter. In addition, the fiber saturation points (FSP) were determined by DSC. The former were performed in an isothermal-step method and the latter using the continuous heating-up method. Native and thermally modified twin samples of Norway spruce (Picea abies (L.) Karst.), Sycamore maple (Acer pseudoplatanus L.) and European ash (Fraxinus excelsior L.) were analyzed. The results clearly show that the pore shares of wood for the measurable diameter range between 4 and 400 nm decrease considerably in all studied wood species due to thermal modification of the wood. Furthermore, thermal modification of wood leads to a decreased FSP for all studied wood species. For evaluation as well as reproducibility of the results of pore-size distribution and FSP, the consideration of sensible heat and specific heat of fusion plays an important role. If this is not done, it can lead to misinterpretations.     

Shear strength of furfurylated,N-methylol melamine and thermally modified wood bonded with three conventional adhesives

The shear strength of furfurylated, N-methylol melamine (NMM) and thermally modified wood bonded with emulsion polymer isocyanate, polyvinyl acetate (PVAc), and polyurethane (PU) adhesives was examined. Furfurylation and NMM modification of Scots pine had a significant negative effect on the bonding strength with all adhesives irrespective of the treatment intensity. The obtained low-shear strength values were related to the brittle nature of the wood after modifications rather to the failure of the bondline. PVAc showed a better bonding performance with both furfurylated and NMM modified wood while the combination of furfurylated wood and PU gave the highest reduction in bonding strength (47–51%). Shear strength also decreased significantly after thermal modification in both Scots pine (36–56%) and beech (34–48%) with all adhesives. With the exception of thermally modified beech samples bonded with PU, bondline was found to be the weakest link in thermally modified wood as it was revealed by the wood failure surfaces. Bondline thickness and effective penetration of adhesives did not relate to the shear strength of all modified wood materials. The lower shear strength of modified wood could be attributed to other factors, such as the reduced chemical bonding or mechanical interlocking of adhesives, and the reduced strength of brittle modified wood substrate.     

Promoting fungal pigment formation in wood by utilizing a modified decay jar method

The role of test block placement within a modified decay jar system for promotion of fungal pigments was investigated. Beech and sugar maple blocks were inoculated with common pigment producing fungi and incubated for 10?weeks. Blocks were placed either below the vermiculite or resting on its surface; no feeder strips were utilized. Amount of pigmentation differed with block placement with Arthrographis cuboidea (on sugar maple and beech) and Xylaria polymorpha (only on sugar maple) producing more pigment when placed on the surface of the vermiculite. The differences in pigmentation, however, were not necessarily due to moisture content differences within test blocks, as moisture content did not vary significantly by block placement with A. cuboidea. Results indicate that placement of wood above vermiculite may increase pigmentation; however, reasons for the increase appear to differ among fungi.     

Effects of shade on growth and mortality of maple (Acer pseudoplatanus), ash (Fraxinus excelsior) and beech (Fagus sylvatica) saplings

We compared shade tolerance of maple, ash and beech in the saplingstage from two sites with rich soils differing in water supply,growing in dense thickets underneath a beech shelterwood ofvarying canopy densities. Shade tolerance was described by twocomponents: mortality in shade and height growth in high light.At low light, beech showed the least mortality, maple the highestand ash in between on both sites. The decline with increasinglight was steepest in beech and more gradual with ash and maple.At 15 per cent above canopy light, all three species approachedzero mortality. Beech as the most shade-tolerant species hadthe highest survival rate under low light and the least lengthgrowth rate under high light (>17 per cent). Ash had a lowersurvival rate at low light than beech and a highest growth rateat high light. Maple showed a bit weaker trade-off with thelowest survival rate but a growth rate inferior to ash. On thebetter water-supplied site, height growth was significantlysuperior in all three species only under high light. On thebasis of these results, silvicultural conclusions are drawnwith respect to appropriate light levels and cutting types.     

Influence of browsing damage and overstory cover on regeneration of American beech and sugar maple nine years following understory herbicide release in central Maine

Northern hardwood stands, notably those with American beech (Fagus grandifolia Ehrh), sugar maple (Acer saccharum Marsh.), and yellow birch (Betula alleghaniensis Britton), are abundant across the forested landscapes of northeastern USA and southeastern Canada. Recent studies have reported an increasing dominance of American beech in the understory and midstory of these forests. Beech is a commercially less desirable tree species due to its association with beech-bark disease, and because it commonly interferes with the regeneration of other more desirable tree species. We examined hardwood regeneration characteristics nine years after application of a 3 × 4 factorial combination of glyphosate herbicide (0.56, 1.12, and 1.68 kg ha^?1) and surfactant concentrations (0.0, 0.25, 0.5, and 1.0% v v^?1) to release sugar maple regeneration from beech-dominated understories using three stands that received shelterwood seed cutting in central Maine. Measurements nine years after treatment showed that glyphosate rate increased both absolute (AD) and relative density (RD) of sugar maple regeneration, but not its height (HT). In contrast, beech AD, RD, and HT were all significantly reduced with increasing glyphosate rate. Post-release browsing by ungulates and a high residual overstory basal area resulted in reduced sugar maple HT. Our results indicated that glyphosate herbicide applied in stands that have been recently shelterwood seed cut can significantly increase the abundance of sugar maple regeneration. However, subsequent browsing damage combined with the negative influence of the residual overstory cover can limit the longer-term benefit of understory herbicide treatments. Subsequent removal of the overstory and browsing-control measures may be needed to promote sugar maple regeneration over beech in similar northern hardwood stands.     

Impregnation of Bombax ceiba and Bombax insigne wood with a N-methylol melamine compound

Methylated N-methylol melamine (NMM) is known for its ability to enhance physico-mechanical properties, anti-fungal ability, and hydrophobicity and was therefore used to impregnate two less used and non-durable wood species from Myanmar, Bombax ceiba and Bombax insigne. Solution uptake, weight percent gain and nitrogen content were increased by increasing melamine concentrations with B. ceiba always achieving higher values compared with B. insigne. According to the leaching results, a higher degree of condensation after curing as well as a better crosslinking of NMM could be obtained at higher temperatures. However, both curing temperatures used (90 and 120 °C) resulted in almost the same amount of nitrogen fixed in the cell wall. UV microspectrophotometry confirmed the penetration of the NMM into different morphological regions of wood tissues, which was again supported by the analysis of point measurement spectra of treated and untreated specimens.     

Development of canopy stratification during early succession in northern hardwoods

Canopy development on a 6-year-old strip cut was analyzed by measuring the heights to terminal buds and bud scale scars of the tallest individuals of each species present on 50 plots of radius 6 m. Phenology of height growth was monitored during the following growing season. Pin cherry (Prunus pensylvania L.), an intolerant short-lived tree, had the fastest growth rate and was on the average the tallest species from the second to the sixth year of regrowth. Although advance regeneration of sugar maple (Acer saccharum Marsh.) and beech (Fagus grandifoloa Ehrh.) were the tallest trees during the first growing season, their slower growth rate insured that they would not keep up with the pin cherry. Trembling aspen (Populus tremuloides Michx.), striped maple (Acer pensylvanicum L.) and yellow birch (Betula alleghaniensis Britt.) occupied an intermediate position in the canopy by the end of the sixth growing season, and showed relatively greater annual height increment than beech or sugar maple. Height growth phenology differed slightly for each species. Beech, ash (Fraxinus americana L.) and sugar maple commenced growth early, grew rapidly and set buds all by 1 August (beech by 15 June). Yellow birch, pin cherry and trembling aspen started growing as early as the others, grew more slowly at first but then grew for a longer period of time. Striped maple seemed to be somewhat intermediate. Growth phenology and growth rate are related to the tolerance and growth form type (e.g. determinate or indeterminate) of the species. The most tolerant species tend to be determinate in growth form, have slower growth rates and complete height growth earlier. The intolerant species tend to be indeterminate, have a faster growth rate and continue to grow for a longer period. These may be mechanisms by which many species can grow together and avoid adverse effects such as suppression.     

Characterization of lignin-derived products from Japanese beech wood as treated by two-step semi-flow hot-compressed water

Japanese beech (Fagus crenata) wood was treated by two-step semi-flow hot-compressed water (the first stage: 230 °C/10 MPa/15 min, the second stage: 270 °C/10 MPa/15 min), and produced lignin-derived products in the hot-compressed water-soluble portions at the first and second stages, and the final residue of the second stage was characterized with alkaline nitrobenzene oxidation method and gel permeation chromatographic analysis. As a result, the lignin-derived products at the first stage, where hemicellulose was also decomposed, consisted of lignin-based monomers and dimers and oligomers/polymers in the water-soluble portion. A large part of the oligomers/polymers was, however, recovered as the precipitate during 12 h setting after hot-compressed water treatment. By the analysis of nitrobenzene oxidation products, there were relatively higher contents of ether-type lignin in the precipitate at the first stage than in original beech wood. Since the ether linkages of lignin are more preferentially cleaved by this hot-compressed water, lignin-based polymeric fractions were flowed out from the porous cell walls from which hemicellulose was removed. On the other hand, at the second stage condensed-type lignin remained in the precipitate and residue. Based on these results, decomposition behavior of lignin in Japanese beech wood as treated by the two-step semi-flow hot-compressed water was discussed regarding the topochemistry of lignin structure.     

Influence of light availability on growth, leaf morphology and plant architecture of beech ( Fagus sylvatica L.), maple ( Acer pseudoplatanus L.) and ash ( Fraxinus excelsior L.) saplings

In a field study, we measured saplings of beech, ash and maple growing in a fairly even-aged mixed-species thicket established by natural regeneration beneath a patchy shelterwood canopy with 3–60% of above canopy radiation reaching the saplings. Under low light conditions, maple and ash showed a slight lead in recent annual length increment compared with beech. With increasing light, ash and maple constantly gained superiority in length increment, whereas beech approached an asymptotic value above 35% light. A suite of architectural and leaf morphological attributes indicated a more pronounced ability of beech to adapt to shade than ash and maple. Beech displayed its leaves along the entire tree height (with a concentration in the middle crown), yielding a higher live crown ratio than ash and maple. It allocated biomass preferentially to radial growth which resulted in low height to diameter ratios, and expressed marked plagiotropic growth in shade indicating a horizontal light-foraging strategy. In addition, beech exhibited the highest specific leaf area, a greater total leaf area per unit tree height, a slightly greater leaf area index, and a greater plasticity to light in total leaf area. Ash and maple presented a “gap species” growth strategy, characterized by a marked and constant response in growth rates to increasing light and an inability to strongly reduce their growth rates in deep shade. In shade, they showed some plasticity in displaying most of their leaf area at the top of the crown to minimize self-shading and to enhance light interception. Through this, particularly, maple developed an “umbrella” like crown. These species-specific responses may be used for controlling the development of mixed-species regeneration in shelterwood systems.     

Tartaric acid catalyzed furfurylation of beech wood

European beech (Fagus sylvatica L.) is a major tree species of European forest which is underexploited because of its low dimensional stability and durability. Similarly to what has been developed with radiata pine, furfurylation might be the answer to optimize the utilization of local beech wood. Beech wood furfurylation process was studied using five different catalysts: maleic anhydride, maleic acid, citric acid, itaconic acid, and tartaric acid. Optimization of the furfurylation process was investigated for different catalyst and furfuryl alcohol (FA) contents, and different duration of polymerization. The following properties were studied: weight percent gain (WPG), leachability, anti-swelling efficiency (ASE), wettability, modulus of elasticity, modulus of rupture, Brinell hardness, and decay durability. Tartaric acid, never investigated up to now, was retained as catalyst to perform furfurylation due to its efficacy compared to other catalysts and its novelty. Wood modification with FA and tartaric acid as catalyst led to samples with high WPG even after leaching, improved ASE, and lower wettability with water. Increasing the polymerization duration increased the fixation of FA in treated wood. Most of all, treatment gave a significant improvement in mechanical properties and resistance to wood decaying fungi.     

Nutrient concentrations in roots, leaves and wood of seedling and mature sugar maple and American beech at two contrasting sites

Differences in sensitivity to soil conditions across tree species and developmental stage are important to predicting forest response to environmental change. This study was conducted to compare elemental concentrations in leaves, stems, and roots of (1) sugar maple (Acer saccharum Marsh.) seedlings vs. mature trees and (2) mature sugar maple vs. mature American beech (Fagus grandifolia Ehrh.) in two sites that differ in soil base saturation and pH. Both sites are located in Huntington Forest, NY, USA; one site (hereafter ‘H’) has higher soil pH and Ca, Mg, and Mn concentrations than the other site (hereafter ‘L’). Sugar maple growth at H (14.8 cm² year⁻¹ per tree) was much greater than at L (8.6 cm² year⁻¹ per tree), but the growth of beech was not different between the two sites. Leaves, roots, and stem wood of mature beech trees and sugar maple seedlings and mature trees were sampled for nutrient analysis. Foliar Ca, K, and Al concentrations were positively correlated with soil elements, but Mn concentrations were negatively correlated. Sugar maple differed more than beech between sites in foliar K and Mn concentrations. Root Mg and P concentrations reflected soil chemistry differences, in contrast to foliar concentrations of Mg and P, which were indistinguishable between the sites. In sugar maple, seedlings differed more than in mature trees in nutrient concentrations in roots, especially for Mg and Mn. Although beech was not as responsive to nutrient availability as sugar maple in foliar and root nutrient concentrations, Ca and Mg concentrations in beech wood were higher in H (52% higher for Ca and 68% higher for Mg), while sugar maple did not differ between sites. Sugar maple regeneration failure on acidic soils in the same region is consistent with our finding that sugar maple seedlings were very sensitive to nutrient availability. This sensitivity could ultimately contribute to the replacement of sugar maple by American beech in regions of low pH and base cations if base cation leaching by anthropogenic deposition and tree harvesting continues.     

Improvement of mechanical properties of thermally modified hardwood through melamine treatment

Specimens of beech, ash, lime and poplar were thermally modified (T) and treated with an aqueous solution of melamine (M) resin to investigate the mechanical changes after combined (double) modification (TM). Density, solution uptake, weight percent gain, bulking and equilibrium moisture content were recorded to ensure proper treatment. Samples for Brinell hardness and three-point bending were cured at 120°C under dry conditions. The WPGs of the two treatment groups M and TM were similar, but bulking of TM specimens was negative. This might indicate an incomplete penetration into the thermally modified cell wall in combination with a potential leaching of soluble hemicellulose components by the alkaline impregnation solution. The decreased hardness of heat-treated wood was substantially increased by melamine treatment (combined modification). Both modifications and their combination slightly increased the modulus of elasticity. The modulus of rupture was increased after melamine treatment, decreased after thermal modification and combined modification. The work in bending was severely reduced for all treatments. Melamine treatment of thermally modified wood was carried out successfully and some mechanical properties were improved. Double-modified wood with increased modulus of rupture (MOR) and extraordinary surface hardness would be suitable for non-structural outdoor applications such as decking and cladding.

Abbreviations: ANOVA: Analysis of variance; EMC: Equilibrium moisture content; EMC_R: Reduced (corrected) equilibrium moisture content; IB: Impact bending strength; M: Melamine treated; MOE: Modulus of elasticity; MOR: Modulus of rupture; MUF: melamine-urea-formaldehyde resin; OD: Oven dry density; R: Untreated references; RH: relative humidity; SC: Solid content; SU: Solution uptake; T: Thermally modified; TM: Thermally modified and melamine treated (double modification); WB: Work in bending; WPG: Weight percent gain     

TEM/FE-SEM studies on tension wood fibres of Acer spp., Fagus sylvatica L. and Quercus robur L.

Tension wood (TW) fibres from maple, beech and oak were analysed with special emphasis on the cell wall fine structure and deposition of aromatic compounds within the gelatinous layer (GL). For this purpose, transmission electron microscopy (TEM) was applied after section staining with potassium permanganate. There was evidence for the occurrence of aromatic compounds in the GLs of fibres of all three species. Some GLs showed a concentric sub-layering. Hence, conclusions about the biosynthetic activities during cell wall formation in TW could be derived. Additional information about structural characteristics of TW fibres were obtained by means of field emission electron microscopy. High-resolution micrographs of cell walls were used for measurements of diameter and microfibril angle (MFA) of cellulose aggregates (CAG). CAG of 7 nm were observed although their diameter varied greatly in the GLs. MFA in the secondary wall of TW was slightly smaller than in opposite wood. The microscopic methods provided complementary ultrastructural and topochemical information on tension wood fibres. The subcellular localisation of aromatic compounds and the observations of the ultrastructural morphology will contribute to the understanding of origin and functionality of TW and its characteristic GL.     

Forest fire effects in beech dominated mountain forest of Iran

Most of world's forests of different climates have a history of fire, but with different severities. Fire regimes for broadleaf deciduous forests have return intervals that vary from many decades (or less) to centuries (or more). Iran has a total of 1.2 million ha of temperate forest in the north, where fires burn about 300–400 ha annually. This study focused on the impact of fire on forest structure, tree species quality, and regeneration composition (specially beech) in the Chelir forest of northern Iran. The results showed that forest fires changed the structure and had different effects on tree species composition between burned and control areas. Thin barked species such as oriental beech (Fagus orientalis Lipsky) and coliseum maple (Acer cappadocicum Gled.) have been affected more than those with thick bark, like hornbeam (Carpinus betulus L.) and chestnut-leaved oak (Quercus castaneifolia C.A. Mey). The density of oriental beech regeneration in the unburned area was greater than in the burned area, while the quantity of regeneration of hornbeam, coliseum maple and velvet maple (Acer velutinum Boiss) was higher in burned area. Forest fire had a greater effect on oriental beech quality, and changed regeneration composition in the burned area. Fire prevention activities should be considered as a silvicultural treatment for preserving these valuable forests.     

Detection of incipient decay in tree stems with sonic tomography after wounding and fungal inoculation

Picus^® acoustic tomography was used to map incipient stages of fungal decay in the sapwood of standing Douglas fir, beech, oak, and sycamore trees 2, 16, and 27 months after wounding and artificial inoculation with brown-, soft-, and white-rot decay fungi. Some wood properties were additionally measured before (velocity of sound) and after (moisture content, weight loss, and density of sound, discoloured and/or decayed wood) tree felling (28 months). With the exception of Trametes versicolor in sycamore, wood decay was not evident from the tomograms in any host-fungus combination. In comparison to measurements after two months, the device recorded a reduction in sound velocity in some host-fungus combinations after 16 and 27 months. In beech, there was a significant reduction in sound velocity after inoculation with Ganoderma applanatum, Kretzschmaria deusta, and Trametes versicolor. Similarly, a reduction in sound velocity was recorded in sycamore inoculated with Kretzschmaria deusta and Trametes versicolor. In all these combinations, losses in wood weight and wood density were also found. Results showed that the detection of incipient fungal decay at the periphery of tree stems needs to be improved such that tomograms of the Picus^® acoustic tomograph are capable of identifying decay progressing from the sapwood inwards.     

Preparation of Chinese fir wood/MMT nanocomposites and the factors affecting it

The nano intercalation compounding of wood and MMT has important implications for the modification of wood and for the development of new materials. With water-soluble phenol formaldehyde resin as an intermediary, the nanocomposites of Chinese fir (Cunninghamia lanceolata) wood and montmorillonite (MMT) were prepared via three impregnation methods, i.e. normal pres-sure, once and twice vacuum methods. Based on the weight percent gain (WPG) of impregnated wood, the effects of compounding wood and MMT in term...     

Evolution of CO2 during the fixation of chromium containing wood preservatives on wood

Summary A titration procedure was used to confirm carbon dioxide evolution from wood treated with solutions containing chromic acid and to quantify the effects of species (red pine vs soft maple), solution concentration and reaction temperature on the rate and amount of CO₂ evolved. Small blocks or chips were vacuum treated with either chromated copper arsenate (CCA) wood preservative or chromic acid solutions and the release of CO₂ monitored until the reaction was complete. Significant volumes of CO₂ were measured. This is attributed to the oxidation and subsequent decarboxylation of primary hydroxyl groups on wood constituents. The ratio of moles of CO₂ produced to moles of chromium added to the wood ranged from about 0.07 to 0.24 depending on the wood species, solution properties and fixation conditions. This accounted for from 9 to 32% of the total oxidation potential of the hexavalent chromium applied. The relative amounts of CO₂ produced were higher for maple than for red pine. The rate of CO₂ evolution was also higher in the maple samples, consistent with the higher rate of chromium reduction in soft maple compared to red pine. The amount of C0₂ produced was approximately proportional to the amount of hexavalent chromium in the CCA treating solution although the ratio of CO₂ produced to chromium added to the wood increased slightly with increasing solution concentration. The relative amounts of CO₂ produced increased with increasing fixation temperature over the 50–90 °C range in both species. The rate of CO₂ evolution was accelerated as the fixation temperature was increased. The rates and amounts of CO₂ produced were similar for CCA and Cr0₃ treatments containing the same concentration of chromic acid. Copper and arsenic components of the CCA solution did not appear to have any effect on the decarboxylation reaction.We gratefully acknowledge the financial support of the Natural Sciences and Engineering Research Council of Canada, Natural Resources Canada;, LPB Poles Inc., Masson Quebec, Timber Specialties Ltd., Campbellville Ontario and Guelph Utility Pole Co. Ltd., Guelph Ont. for this study.     

The effects of wood species and treatment retention on kinetics of CCA-C fixation reactions

Reaction kinetics of fixation of CCA-C (chromated copper arsenate type C) preservative was studied at 30°C in ground wood of trembling aspen, red pine, and red maple at treatment retentions of 4.0, 6.4, 9.6, and 30 kg/m³, and red maple pre-extracted with hot water at retentions of 6.4 and 30 kg/m³. Reaction orders of cumulative Cr, Cu, and As reactions decreased gradually during the fixation if calculated by Van’t Hoff’s method. With Essen’s method, CCA fixation was best approximated as follows: Cr—3rd order reaction during the first 24 h, and 1st order reaction for the rest of the fixation period; Cu—2nd order reaction; and As—1st order reaction in red pine and aspen, and 2nd order in red maple. Rates of reaction decreased with increased CCA solution concentration for Cr and Cu, and increased for As, except in red maple. Reaction rates for all CCA elements were significantly higher in rapidly fixing red maple than in regularly fixing red pine and aspen, and were higher in unextracted than pre-extracted red maple. Modeling of CCA fixation kinetic for the whole fixation period enabled comparison of fixation reactions among wood species, preservative components, and treatment retentions.