Effects of site on fibre, kraft pulp and handsheet properties of Eucalyptus globulus

? Eight-year old trees from two Eucalyptus globulus Labill. clones planted across three different sites in Tasmania, Australia, were sampled for wood and kraft pulp/handsheet properties.

? Site had a significant effect on all measured properties. Compared with the poor site (Parkham) the wood from the good site (West Ridgley) had on average 11 % lower wood density. The poor site had also greater microfibril angles, shorter fibres at lower pulp yields.

? The handsheets produced with pulp from the poor site resulted in comparatively higher bulkiness, lower burst, lower tear and tensile indices, lower zero span tensile strength, but higher opacity, higher light scattering and higher surface roughness. Significant height effects were found with all wood properties, and also with tear index, zero span tensile strength and opacity.

? Discriminant analysis showed that for 76 out of 100 handsheets the raw material source, i.e. growth site, could be predicted correctly using a set of handsheet properties with tear index and bulk index being most prominent.

? This is unique evidence that site conditions are strongly reflected in handsheet properties produced from Eucalyptus pulp.

     

Variation in the natural termite resistance of teak (Tectona grandis Linn. fil.) wood as a function of tree age

? Tree age is one of the most important factors to affect the natural durability of wood.

? The purpose of this study was to determine the natural termite resistance of heartwood and sapwood of teak (Tectona grandis Linn. fil.) for trees aged 8, 30 and 51 years. Reticulitermes speratus Kolbe was employed as a test termite using a no-choice feeding method.

? The heartwood and sapwood of all of the trees tested exhibited antitermitic activity. Based on the mean mass loss due to termite activity, the sapwood and heartwood regions of 8-year-old trees are the most susceptible to termites while the heartwood regions of the 30-year-old trees showed termite resistance similar to the termite resistance of 51-year-old trees.

? The mass loss is moderately correlated with n-hexane extractive content, total extractive content, brightness and redness of the wood.

     

Variations in water use by a mature mangrove of Avicennia germinans, French Guiana

? In the tropical intertidal zones, little is known on water uptake by mangroves. Transpiration rates are generally measured at leaf level, but few studies exist on water use at tree or stand levels.

? The objective of this study was to measure sap flow in trees of different sizes to appreciate the range of variation in water use that may exist in a site dominated by 80% mature Avicennia germinans.

? The results showed that from the dry to the wet season the mean water use increased from 3.2 to 5.3 dm³ d^?1 in small trees (DBH ～ 13 cm), from 11.5 to 30.8 dm³ d^?1 in medium trees (～24 cm) and from 40.8 to 64.1 dm³ d^?1 in large ones (～45 cm).

? Sapwood remained active up to a depth of 8 cm with radial variations within the stem. Weak correlations were obtained with VPD and net radiation.

? This study confirmed that transpiration was larger under low levels of salinity. Water use at stand level (～1900 living stems ha^?1) was estimated to be in the range of 5.8 to 11.8 m³ ha?1 d^?1 according to the season.

     

Site preparation and competing vegetation control affect loblolly pine long-term productivity in the southern Piedmont/Upper Coastal Plain of the United States

? A site preparation study was established in 1986 to evaluate the effect of different site preparation treatments on growth and yield of loblolly pine (Pinus taeda L.) plantations on the Piedmont and Upper Coastal Plain regions of the southern United States. Site preparation treatments included: (1) burn only, (2) chop-burn, (3) shear-pile-disk, (4) chop-herbicide-burn, (5) herbicide-burn, and (6) herbicide-burn-herbicide.

? The data from the available 19 installations at age 21 were analyzed with separate analysis of variance and a multilevel nonlinear mixed-effects modeling approach.

? The herbicide-burn-herbicide treatment significantly increased average Dbh, height, basal area and volume per hectare compared to all other treatments. The burn only treatment consistently ranked worst and was followed by the chop-burn treatment. The shear-pile-disk and chop-herbicide-burn treatments had similar overall growth pattern, and will approach the same level of pine volume as the herbicide-burn treatment.

? Loblolly pine mean annual increment in volume (m³ ha^?1 y^?1) at age 21 by treatment were: herbicide-burn-herbicide (17.9), shear-pile-disk (16.1), herbicide-burn (15.9), chop-herbicide-burn (15.4), chop-burn (14.3), and burn (11.2).

? An additional chop or herbicide treatment to the burn treatment significantly increased loblolly pine yield. Complete control of both herbaceous and woody completion enhanced long-term pine productivity.

     

High vs. low yielding oleoresin Pinus halepensis Mill. trees GC terpenoids profiling as diagnostic tool

? A discriminant study based on samples taken from high and low yielding oleoresin trees of two Greek populations, Chalkidiki and Euboia, was carried out. Oleoresin of Pinus halepensis Mill. was characterised by GC/MS analysis.

? The objectives of this study were: (i) to identify in detail the composition of the oleoresin of P. halepensis and in particular of high yielding trees (plus trees) (ii) to investigate a potential relationship between the oleoresin compounds and the oleoresin yield and (iii) to investigate any correlations among the compounds.

? About forty monoterpenes, sesquiterpenes and diterpenes were identified as main compounds representing 97.40% of the analyzed oleoresin. α-Pinene, methyl abietate, abietic acid, palustric acid, isopimaric acid and neoabietic acid were the major compounds. Efficient discrimination was achieved between the two populations and between the two groups of trees (high and low yielding). In both cases, the differentiation was due to the quantitative variability of certain compounds. High positive correlations were found among certain compounds.

? The results suggest that the oleoresin profile is a useful tool for the discrimination of trees according to their provenance or their oleoresin yield.

     

Correction of moisture effects on near infrared calibration for the analysis of phenol content in eucalyptus wood extracts

? Methods based on near infrared spectroscopy used to assess wood properties are susceptible to variations in physical parameters (temperature, grain size, etc.). As wood is a hygroscopically sensitive material, we studied the effects of moisture on near infrared absorbance and calibration to accurately determine the application potential of this technique under routine.

? A collection of Eucalyptus urophylla × E. grandis hybrid wood pieces were analysed to obtain reference calibration of polyphenol contents in wood extracts via NIR spectra acquired under constant moisture conditions. Other specimens from the same source were assessed to obtain spectra for eight moisture contents spanning a broad variation range. The effects of moisture on absorption and on estimates based on a reference model were analysed.

? An increase in moisture content prompted a rise in near infrared absorption over the entire spectrum and for water O-H absorption bands. The polyphenol content estimates obtained by assessing specimens against the reference calibration at variable moisture contents revealed prediction bias. Five correction methods were then tested to enhance the robustness relative to moisture.

? In-depth calibration and external parameter orthogonalization (EPO) were found to be the most efficient methods for offsetting this factor.

     

Radial distribution of quinones in plantation teak (Tectona grandis L.f.)

? Quinones are primarily responsible for the natural durability of teak.

? The previous paper in this series reported on the natural termite resistance of teak trees of different ages (8-, 30- and 51-year-old trees). In this study, the radial distribution of quinones (tectoquinone, lapachol, desoxylapachol and its isomer) and other components in the ethanol-benzene (1:2) extract were measured by means of gas chromatography.

? Significant differences in desoxylapachol or its isomer content were found among the outer heartwood of 8-, 30- and 51-year old trees, as well as between the inner and outer parts of the heartwood.

? All toxic quinone contents were positively correlated with the total extractive content. The highest correlation degree was measured in the isodesoxylapachol content.

? Although linearly related, only modest correlations were observed between the natural termite resistance parameters and the content of tectoquinone and isodesoxylapachol.

     

A generic model of thinning and stand density effects on forest growth, mortality and net increment

? For assessing forest thinning effects at large (i.e. continental) scale, data scarcity and technical limitations prevent the application of localized or individual-based thinning models.

? Here we present a simple general framework to analyze and predict the effects of thinning on growth and mortality, including the following stand density development. The effects are modeled in relative terms so that the model can be parameterized based on any thinning experiment that includes an unthinned control, regardless of site conditions and stand age.

? The model was tested against observed thinning effects on growth and mortality from five temperate and boreal species (all species pooled r ² = 0.51). It predicted a maximum increase in net stem biomass increment of 16% and a reduction in density-related mortality of 75% compared to un-thinned conditions at stand densities of around 70% of the maximum (increment optimal density).

? A sensitivity analysis revealed overlapping ranges of near optimal density (net increment within 95% of optimal) among all tested species, suggesting that one thinning scenario can be used for many species. The simple and general formulation of thinning effects based on only five parameters allows easy integration with a wide range of generic forest growth models.

     

Comparing volume growth in pure and mixed stands of Pinus sylvestris and Quercus pyrenaica

? In Mediterranean forestry, it is important to improve knowledge about mixed stands dynamics, including their productivity. Previous studies have focused on the interactions between different species (competition, reduction of competition and facilitation) depending on site, species composition and structure.

? At the centre of this research are the possible differences between pure and mixed stands of Pinus sylvestris and Quercus pyrenaica in terms of density-growth relationships and volume growth per species.

? Using data from the second and third Spanish National Forest Inventory (606 plots), volume increment models for these species were fitted. Both species displayed a similar density-growth pattern for pure and mixed stands, with a maximum volume growth at maximum density. Volume increment per occupied area was also found to be greater in mixed stands as opposed to pure stands, suggesting a species interaction with reduced levels of competition in the former. However, the total volume growth was generally lower in mixed stands since the growth rate of oak is much lower.

? The results highlight the expedience of favouring P. sylvestris-Q. pyrenaica mixed stands with higher proportions of pine trees in order to gain the benefits of a more complex forest whilst retaining an acceptable level of wood production.

     

Diminished vessel diameter as a possible factor in the decline of European ash (Fraxinus excelsior L.)

? The aim of this work was to examine the anatomy and functioning of secondary xylem in stems in relation to the decline of European ash (Fraxinus excelsior L.).

? We tested the hypothesis that declining trees show changes in the structure of wood, which result in impaired water transport.

? Anatomical analyses were carried out on wood samples (comprising all annual rings formed during the 30 years life of the analysed trees) collected at breast height from the main stem of healthy, weakened and dead ash trees. The width of annual wood increments, the diameter and density of earlywood vessels were measured and the theoretical hydraulic conductivity index through the secondary xylem calculated by application of Hagen-Poisseuille’s formula.

? Anatomical characteristics changed both with the age of trees and in response to unfavorable factors. The largest vessels were observed in healthy trees, which implied that they had the highest hydraulic conductivity index, whereas trees considered to be in decline produce smaller vessels and hence had reduced conductivity.

     

Diachronic analysis of individual-tree mortality in a Norway spruce stand in the eastern Italian Alps

? Understanding tree mortality processes across time requires long term studies. Spatiotemporal patterns of mortality in a 200 years-old mono-layered Norway spruce stand were evaluated to determine what factors affected individual-tree mortality.

? We performed an analysis on two surveys (1993 and 2005) in a 1-ha permanent plot in the Paneveggio forest (Eastern Italian Alps). Tree diameter and age distribution between surveys were compared. We examined spatial patterns of living and dead trees before 1993, in 1993 and in 2005 using univariate and bivariate Ripley’s K(d) function, and a kernel estimator of local crowding. A logistic model was used to assess the effects of diameter, age, recent growth and competitive pressure on tree mortality.

? Spatial pattern analysis indicated mortality was associated to tree neighbourhood (neighbour effect at 2–5 m). An increment of regularization of tree spatial pattern occurred due to density-dependent mortality. Logistic regression showed tree diameter and recent growth were determinant on mortality risk during the monitoring period.

? Even if the stand is relatively aged, mortality dynamics are those typical of stem exclusion stage. Mortality was related to competitive dynamics, and small suppressed trees with slow growth rate had higher probability to die.

     

Is forest mushroom productivity driven by tree growth? Results from a thinning experiment

? Most of the edible forest mushrooms are mycorrhizal and depend on carbohydrates produced by the associated trees. Fruiting patterns of these fungi are not yet fully understood since climatic factors alone do not completely explain mushroom occurrence.

? The objective of this study was to retrospectively find out if changing tree growth following an increment thinning has influenced the diversity patterns and productivity of associated forest mushrooms in the fungus reserve La Chanéaz, Switzerland.

? The results reveal a clear temporal relationship between the thinning, the growth reaction of trees and the reaction of the fungal community, especially for the ectomycorrhizal species. The tree-ring width of the formerly suppressed beech trees and the fruit body number increased after thinning, leading to a significantly positive correlation between fruit body numbers and tree-ring width.

? Fruit body production was influenced by previous annual tree growth, the best accordance was found between fruit body production and the tree-ring width two years previously.

? The results support the hypothesis that ectomycorrhizal fruit body production must be linked with the growth of the associated host trees. Moreover, the findings indicate the importance of including mycorrhizal fungi as important players when discussing a tree as a carbon source or sink.

     

The potential of plantations of Terminalia superba Engl. & Diels for wood and biomass production (Mayombe Forest, Democratic Republic of Congo)

? In the 1940s–1950s, large limba (Terminalia superba Engl. & Diels) plantations were established in the Democratic Republic of Congo to reduce the pressure on the natural forests.

? The objective of this study was to evaluate the potential of these long-rotation plantations as production forests (timber) and carbon sinks.

? Five different plantations, between 50 and 58 years old, were sampled. Over a sample surface of more than 73 ha, the diameter above buttresses of 2 680 trees, bole height of 265 trees and tree height of 128 trees was measured.

? To estimate the commercial volume, a nonlinear power law regression was used (R ² = 0.95). A power law variance function was applied to counter heteroscedasticity of the residual plot. Estimates of commercial tree and stand volume at 50 to 58 y were 5.6 ± 4.1 m³ and 183.9 ± 135.0 m³ ha^?1. Stand volumes appear low but are explained by a large decrease in tree density. However, the mean volume increment of 3.2–3.7 m³ ha^?1 y^?1 corresponds well with teak plantations of a similar age. For limba, aboveground biomass and carbon estimates of this study (resp. 108.4 and 54.2 Mg ha^?1) differ significantly from those of existing aboveground biomass models (resp. 135.7–143.9 Mg ha^?1 biomass and 67.9–72.0 Mg ha^?1 C). All aboveground biomass and carbon estimates for T. superba stands were lower than for the estimates of young fast-growing plantations like Tectona grandis L. f., Eucalyptus spp. and Acacia spp. (≤ 30 y).

     

Lifespan and mortality of old oaks — combining empirical and modelling approaches to support their management in Southern Sweden

? Old oaks (Quercus robur L.) play an important role in the southern Scandinavian landscape by providing habitat for a wide range of species, a large proportion of them being currently on the National Redlists.

? To provide support for the management of these trees, we review data on oak mortality and formulate a mortality-driven stochastic model analysing interactions between mortality rate, oak recruitment rate into 100–150 age class, and amount of oaks older than 200 years.

? Empirical annual mortality rates varied between 0 and 13% with average 1.68%. Trees older 200 years had an average mortality rate of 1.1%. Oaks in the high density forests showed higher mortality (3.2%) as compared to the trees growing in the low density forests (1.2%). A 400-year long modelling exercises indicated that under current mortality rates (regular mortality being centred around 1% annually; and irregular mortality 7% with average return time of 13 years) the long-term maintenance of 20 trees older than 200 years per ha would require an input rate of 1 to 5 trees × year^?1 × ha^?1 into the 100–150 years old class.

? The modelling highlighted the importance of initial oak abundance affecting amount of old trees at the end of shorter (100 years) simulation period.

     

Physical properties of wood in thinned Scots pines (Pinus sylvestris L.) from plantations in northern Spain

? The physical properties of wood and the associated variations within and between trees were evaluated by analysing 770 small specimens of clear wood from 11 Pinus sylvestris L. trees thinned from 3 plantations.

? Within-tree variations in basic density or volumetric shrinkage increased with cambial age and decreased with increasing ring width. The effect of the height in the stem on wood properties was considered indirect and height was not included as an explanatory variable in the mixed models proposed to estimate basic density and volumetric shrinkage.

? The models had random components for the intercept parameter and explained 52.5% of the total variance in basic density and 56% of the total variance in volumetric shrinkage. Linear shrinkage in the direction of the grain was extremely variable.

? Between-tree variation and between-plot variation in the physical properties of wood were high, considering that all trees sampled were growing in similar sites and stands. It would then be desirable to predict physical properties of wood on living trees in order to use the quality of wood as a criterion for timber tree selection in thinnings.

     

Tree diameter, height and stocking in even-aged forests

? Empirical observations suggest that in pure even-aged forests, the mean diameter of forest trees (D, diameter at breast height, 1.3 m above ground) tends to remain a constant proportion of stand height (H, average height of the largest trees in a stand) divided by the logarithm of stand density (N, number of trees per hectare): D = β(H ? 1.3)/ ln(N).

? Thinning causes a relatively small and temporary change in the slope β, the magnitude and duration of which depends on the nature of the thinning.

? This relationship may provide a robust predictor of growth in situations where scarce data and resources preclude more sophisticated modelling approaches.

     

Effects of climate variables on intra-annual stem radial increment in Pinus cembra (L.) along the alpine treeline ecotone

? Within the alpine treeline ecotone tree growth is increasingly restricted by extreme climate conditions. Although intra-annual stem growth recorded by dendrometers can be linked to climate, stem diameter increments in slow-growing subalpine trees are masked by changes in tree water status.

? We tested the hypothesis that intra-annual radial stem growth in Pinus cembra is influenced by different climate variables along the treeline ecotone in the Austrian Alps. Dendrometer traces were compared with dynamics of xylem cell development to date onset of cambial activity and radial stem growth in spring.

? Daily fluctuations in stem radius reflected changes in tree water status throughout the treeline ecotone. Extracted daily radial increments were significantly correlated with air temperature at the timberline and treeline only, where budburst, cambial activity and enlargement of first tracheids also occurred quite similarly. A close relationship was detected between radial increment and number of enlarging tracheids throughout the treeline ecotone.

? We conclude that (i) the relationship between climate and radial stem growth within the treeline ecotone is dependent on a close coupling to atmospheric climate conditions and (ii) initiation of cambial activity and radial growth in spring can be distinguished from stem re-hydration by histological analysis.

     

Ranking larch genotypes with the Rigidimeter: relationships between modulus of elasticity of standing trees and of sawn timber

? Direct assessment of modulus of elasticity (MOE) on standing trees is attractive for breeders to evaluate genotypes prior to selection: this can be done using the Rigidimeter, a bending-based measurement device.

? In this study, we tested its reliability to properly rank genotypes by relating trunk MOE with MOEs estimated with a vibrating analysis system (Bing) on different types of conditioned wood specimens from the same trees (boards and standardised 2×2×30 cm-clear-wood specimens). One hundred and ten trees from different genotypes of hybrid larch (Larix × eurolepis) were tested.

? Mean trunk MOE was 7 300 MPa with a similar value obtained for sawn boards. Clear-wood specimens MOE increased from pith to bark from less than 6 000 MPa to nearly 9 000 MPa. Moderate correlations (r = 0.48–0.61) were found at the individual tree level between trunk MOE and MOE of wood samples.

? Single specimen MOE was shown to be strongly related to a linear combination of trunk MOE and sample position.

? At the genotype mean level, trunk MOE was highly correlated with wood samples MOE (r = 0.80–0.91). Ranking of genotypes based on trunk MOE was mostly consistent with that based on standardised specimens.

? It was concluded that besides other operational advantages which are discussed, the Rigidimeter is a valuable tool for breeders to routinely evaluate and rank genotypes for stiffness prior to further selection.

     

A comparison of mortality rates between top height trees and average site trees

? Although comparisons between methods of selecting trees for site index estimates are well documented in the literature, little is known on mortality rates of different canopy tree cohorts used for that purpose.

? This study was initiated to test the hypothesis that the mortality rates of top height trees are lower than those of codominants only or a combination of codominant and dominant trees. To test this hypothesis, we used records from a network of permanent sample plots in Québec and studied the fate of different cohorts of site trees for five different species.

? Our results did not show clear evidence of lower mortality rates for top height trees. Instead we found that depending on the species, top height trees have lower (Populus tremuloides, Pinus banksiana), higher (Picea mariana, Abies balsamea) or equal mortality rates (Betula papyrifera) than codominant trees or codominant and dominant trees combined.

? These results suggest a tendency for shade intolerant species to maintain lower top height tree mortality rates over time when compared to shade tolerant species. In the latter case, it is also shown that spruce budworm epidemics (Choristoneura fumiferana) did not change the pattern of mortality rates of site trees of A. balsamea.

     

Gender, neighboring competition and habitat effects on the stem growth in dioecious Fraxinus mandshurica trees in a northern temperate forest

? This study analyses the sex ratios, and the effect of gender, neighboring competition and habitat factors on the stem growth of dioecious F. mandshurica trees in the Changbai Mountains of North-Eastern China.

? The general sex ratio of the flowering trees did not significantly deviate from 1:1. The sex ratio varied among age classes. A female-biased sex ratio was found in the age classes of 65–75 years and 85–95 years, but departure from 1:1 was not significant in other age classes.

? An analysis of variance revealed that the growth rate was extremely sensitive to gender and tree size, as shown by a highly significant gender-related and size-dependent effect. Male trees had a faster stem growth rate than female trees, and the assumption is that trade-offs between reproductive and vegetative processes can induce the difference in stem growth rate between genders.

? Stem growth rates are positively affected by soil moisture and tree size for both genders at all considered neighborhood distances. The growth rates of female trees were negatively affected by neighboring competition from other female trees at all neighborhood distances between 1 and 10 m, but were not significantly affected by male trees. The growth rates of male trees were negatively affected by neighboring competition from male trees for neighborhood distances between 3 and 10 m, but were not significantly affected by female trees.

? These results suggest that intrasexual competition (male-male competition and female-female competition) may cause difference in stem growth for both genders. Intersexual differences in sensitivity to neighboring plants are considered to be an important factor driving gender-specific growth patterns.