Showing papers in "Annals of Forest Science in 2009"

The influences of forest stand management on biotic and abiotic risks of damage

Abstract: • This article synthesizes and reviews the available information on the effects of forestry practices on the occurrence of biotic and abiotic hazards, as well as on stand susceptibility to these damaging agents, concentrating on mammal herbivores, pest insects, pathogenic fungi, wind and fire. • The management operations examined are site selection, site preparation, stand composition, regeneration method, cleaning and weed control, thinning and pruning, and harvesting. For each of these operations we have examined how they influence the occurrence of biotic and abiotic damaging agents, the susceptibility of European forests, and describe the ecological processes that may explain these influences. • Overall, we find that the silvicultural operations that have the largest influence on both biotic and abiotic risks to European forest stands are closely related to species composition and the structure of the overstorey. Four main processes that drive the causal relationships between stand management and susceptibility have been identified: effect on local microclimate, provision of fuel and resources to biotic and abiotic hazards, enhancement of biological control by natural enemies and changes in individual tree physiology and development. • The review demonstrates an opportunity to develop silvicultural methods that achieve forest management objectives at the same time as minimising biotic and abiotic risks. Mots-cles : sylviculture / peuplement / occurrence / sensibilite /

Natural stand structures, disturbance regimes and successional dynamics in the Eurasian boreal forests: a review with special reference to Russian studies.

Abstract: • This review summarizes early stand-scale studies of pristine forest structures, disturbance regimes and successional patterns carried out in boreal Eurasia. We attempt to reveal, characterize and classify stand dynamic types that can be used as templates for nature-based forest management. • The studies reviewed demonstrate multiple successional pathways in stand development in all types of pristine forests. All-aged stands driven by small-scale disturbances are formed over successional development of several hundreds of years. This endogenous development can be interrupted by standreplacing or partial disturbances leading to successions with even-aged or cohort-structured stands, respectively. In Western Europe, the most common disturbances are windthrows, surface fires and fluctuations in moisture regime; in Eastern Europe and Siberia, the most common disturbances are crown and surface fires and insect outbreaks. Type, return interval and severity of disturbances are strongly influenced by the site conditions and successional stage of a stand. • Based on characteristics of forest stands and disturbance regime, four main types of pristine boreal forest stand dynamics can be distinguished: (1) even-aged, compositional change dynamics, (2) evenaged, mono-dominant dynamics, (3) cohort dynamics and (4) fine-scale gap dynamics. These types can be mimicked in developing scenarios of ecological sustainable forest management in Eurasian boreal forests.

Stimulation of tree defenses by Ophiostomatoid fungi can explain attack success of bark beetles on conifers

Abstract: • Our aim is to present why the hypothesis, that Ophiostomatoid fungi play an important role in the establishment of most bark beetle species on living conifers, is valuable.• After summarizing knowledge about the relationships of bark beetles with conifers and fungi, we conclude that controversy results from misinterpretations when using fungal pathogenicity to demonstrate the role of Ophiostomatoid fungi in beetle establishment on host trees.• We demonstrate that fungal pathogenicity is not the right parameter to appreciate the role of fungus in beetle establishment on host trees. We argue that artificial low density inoculations that allow the appreciation of fungus ability to stimulate tree defenses and thus to help beetles in overcoming tree resistance must be used in complement to mass inoculations. In both cases, results must be expressed in terms of tree defense stimulation rather than in terms of tree killing. (i) Fungal species stimulating tree defenses are generally not those that grow the best in the sapwood. (ii) We argue that beetle development in the phloem, fungal invasion of the sapwood and phloem, and tree death, occur after tree defenses are exhausted, and that any fungus present in the beetle gallery could thus potentially invade the sapwood after defense exhaustion. • We conclude that stimulation of the tree defense reactions in both the phloem and the superficial sapwood is a real benefit brought by fungi to the beetles during the first phase of establishment (overcoming tree resistance).• Considering the origin of the bark beetle fungus associations attacking living trees and their general functioning based on stimulation of tree defenses, we develop three hypotheses: (i) any beetle species would be helped in its establishment in a given tree species by developing an association, even loosely, with a fungus species belonging to the Ophiostomatoid flora of that tree species; (ii) the necessity of a considerably low level of tree resistance for fungus extension into the tree is the selection pressure that has led fungi to develop their intrinsic ability to stimulate tree defenses, through their ability to grow into the phloem. This association can be completed by antagonistic fungal species controlling extension of the previous fungal species in the tree tissues; (iii) Beetle species using the strategy of overcoming tree resistance are associated with a fungal complex, of which species could assume three roles regarding relationships between beetles and trees: 1- to stimulate tree defenses in the phloem and superficial sapwood, 2- to grow into the sapwood after tree resistance is overcome, and 3- to control phloem extension of the first other two categories. Bringing nutrients to the beetle progeny can be a fourth role. • We propose that bark beetle – Ophiostomatoid associations can be categorized, based on associations’ frequency and complexity while taking into account beetle aggressiveness. We show that a close correspondence exists between beetles’ aggressiveness and the ability of their main associated fungal species to stimulate the defenses of their host tree.• We conclude with suggesting that most sapwood invading fungi might be “cheaters” which have taken advantage of the efficiency of the relationship between beetles and fungi that stimulate tree defenses.

Combining forest structure data and fuel modelling to classify fire hazard in Portugal

Abstract: • Fire management activities can greatly benefit from the description of wildland fuel to assess fire hazard. • A forest typology developed from the Portuguese National Forest Inventory that combines cover type (the dominant overstorey species) and forest structure defined as a combination of generic stand density (closed or open) and height (low or tall) is translated into fuel models. Fire behaviour simulations that accounted for the fire environment modification induced by stand structure resulted in an objective and quantitative assessment of fire hazard for 19 forest types.

Leaf water status and stem xylem flux in relation to soil drought in five temperate broad-leaved tree species with contrasting water use strategies

Abstract: • Five temperate broad-leaved tree species were compared with respect to their water consumption strategies under ample and restricted water supply. We measured synchronously leaf conductance (gL) in the sun canopy, xylem sap flux (Js) and leaf water potential (predawn, Ψpd and noon, Ψnoon) in adult trees in a mixed stand and related them to the fluctuations in vapor pressure deficit (D )a nd soil moisture. • Maximum gL was particularly high in F. excelsior, C. betulus and T. cordata and revealed a higher D sensitivity. Ψpd remained constantly high in A. pseudoplatanus, C. betulus and F. excelsior ,b ut decreased in T. cordata and F. sylvatica with decreasing soil moisture. • Jsd decreased linearly with decreasing soil matrix potential in all species except for F. excelsior. Apparent hydraulic conductance in the soil-to-leaf flow path (Lc) was higher in A. pseudoplatanus than in the other species. • F. sylvatica maintained a low maximum gL and reduced Jsd markedly upon drought, but faced severe decreases in Ψpd and Ψnoon. F. excelsior represents an opposite strategy with high maximum gL and stable Ψpd. • The species drought sensitivity increases in the sequence F. excelsior < C. betulus < T. cordata < A. pseudoplatanus < F. sylvatica.

Influence of several tree traits on rainfall partitioning in temperate and boreal forests: a review

Abstract: • In forests, rainfall is partitioned into intercepted water (IW), throughfall (TF) and stemflow (SF). We reviewed the majority of published works comparing water flows among tree species in temperate and boreal forests to test the effect of several tree traits on water flows. • We hypothesized that water flows differed between evergreen and deciduous species, and according to successional status and bark roughness. We also investigated that water flows would be explained by stand variables such as basal area. • Linear mixed models fitted on reviewed data showed that evergreens had a lower TF than deciduous trees (decrease of 13.9% of total precipitation year-round and 8.4% over the growing period). Similar results were found for conifers compared to broadleaves. TF also declined with the successional status from pioneer to late-successional tree species. SF decreased with bark roughness from smoother to rougher bark. Evergreens had water flows that were dependent on age of the stand, especially for TF which increased by 15.6% of total precipitation from young to adult forests. • The large scale of TF differences between tree genera together with specific transpiration amounts and rooting features highlighted in other studies should result in significant differences in soil water content among tree species. This may have consequences on stand fitness and growth, and understory vegetation.

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

Abstract: • 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.

Biomass component equations for Latin American species and groups of species

Abstract: • Studies dealing with the estimation of biomass, site productivity and the contribution of forests to the global carbon balance require the use of allometric equations. There have been a great number of equations developed to estimate biomass components of trees and shrubs in various ecosystems. However, there are less literature compilations that address the calculations of biomass components. • I report a total of 229 sets of allometric equations to estimate biomass components for 102 species in 72 different forest communities of arid, semi-arid, subtropical, tropical and temperate Latin-American ecosystems. • The selection of the appropriate allometric model is a key element in the accurate estimation of biomass, stand productivity, carbon stocks and fluxes, and as a consequence, it is important to apply special effort to the selection and estimation of biomass equations. • I also discuss statistical methods of parameter estimation and recommend the dissection of two conventional allometric equations when biomass studies are conducted on a wide range of diameters. In order to use nondestructive procedures of biomass estimation such as the fractal theory, the null hypothesis that the mean slope b value is equal to 2.67 was rejected for Latin American biomass

Climate-growth variability in Quercus ilex L. west Iberian open woodlands of different stand density

Abstract: • We present the longest tree-ring chronology (141 y) of Quercus ilex L. (holm oak), and discuss the species climate-growth relationships and the influence of stand density on tree sensitivity to climate. • Similarly to Quercus suber L., the most influential climatic variables upon holm oak growth were late spring and early summer precipitation, which enhanced growth, and high temperatures in the previous August and current July, which negatively affected growth. • High density stands responded to similar climatic factors as low density stands, but their response was generally weaker. Holm oak sensitivity to climate has increased in recent decades, which might be related to increasing temperatures in the region. Sensitivity was higher in low density stands. Additionally, the effect of summer stress on growth seems to have increased during the same period, similarly to other species in the Iberian Peninsula, suggesting that trees are more vulnerable to climatic changes. • Stand density could buffer the response to climate by smoothing climatic extremes. Nevertheless, the effect of competition might reverse this positive effect at the individual tree level. Precautions should be taken before providing management guidelines regarding the effect of climate change and stand density on holm oak.

Measuring wood density by means of X-ray computer tomography

Abstract: • Wood density is a characteristic of major interest. Usually, it is used as an indicator of wood quality; however, in the context of global change, it is increasingly used for biomass and carbon storage estimations. X-ray computer tomography is a method which enables quick estimates of wood density after applying a calibration procedure. • A review of the literature is presented in this article. Most of the previous studies have been performed in the 80’s or at the beginning of the 90’s. • In this study, the relationship between wood density and Hounsfield numbers was investigated using a recent medical scanner. A linear relationship was fitted using a calibration data set which consisted in tropical wood samples representing a large range of densities ranging between 133 and 1319 kg m−3, and then validated using an independent data set (mainly temperate tree species). The fitted relationships were very strong (R2 > 0.999), whichever the tested scanner settings, with slight but significant effects of the current voltage and reconstruction filters. The RMSE values computed from the validation data set ranged between 5.4 and 7.7 kg m−3 for densities ranging between 364 and 821 kg m−3. • In conclusion, this method of calibration enables the use of a medical scanner to obtain maps of wood density, in a fast and non destructive way, and with a very good accuracy. Very interesting perspectives are opened regarding biomass distribution within trees.

X-ray tomography as a tool for detailed anatomical analysis

Abstract: • Wood identification, anatomical examination and retrieval of quantitative information are important aspects of many research disciplines. Conventional light microscopy with a camera and (semi)-automatic image analysis software is an often used methodology for these purposes. More advanced techniques such as fluorescence, scanning electron, transmission electron, confocal laser scanning and atomic force microscopy are also part of the toolset answering to the need for detailed imaging. • Fast, non-destructive visualization in three dimensions with high resolution combined with a broad field of view is sought-after, especially in combination with flexible software. • A highly advanced supplement to the existing techniques, namely X-ray sub-micron tomography, meets these requirements. It enables the researcher to visualize the material with a voxel size approaching < 1 μm for small samples (< 1 mm). Furthermore, with tailor-made processing software quantitative data about the wood in two and three dimensions can be obtained. Examples of visualization and analysis of four wood species are given in this paper, focusing on the opportunities of tomography at micron and sub-micron resolution. • X-ray computed tomography offers many possibilities for material research in general and wood science in specific, as a qualitative as well as a quantitative technique.

Comparing needle and shoot phenology with xylem development on three conifer species in Italy

Abstract: • Since the 1960s biologists have been trying to assess factors affecting cambial activity and latewood formation. A comparison of the phenology of the apical and lateral meristems could add new clues in order to understand mechanisms of the growth dynamic in conifers. • This study compared needle and shoot growth with xylogenesis in Larix decidua, Pinus cembra and Picea abies during 2001 to verify if cambial resumption occurred after shoot and needle growth had begun, and if latewood initiation occurred when shoot lengthening was complete. • In pine and spruce, needle and shoot lengthening was synchronous between mid-June and August while larches showed an early development of the needles at the end of May with a later shoot lengthening. Cell production lasted from mid-May to the beginning of August, with the first differentiating cells observed at the end of May, which indicated a earlier reactivation of the cambium with respect to needle and shoot growth.The first latewood cells began wall thickening between July and August, during the termination of needle and shoot lengthening. • The hypothesis that cambial resumption occurs after shoot and needle elongation was rejected. The separation in time between apical growth and secondary wall thickening of latewood suggested the presence of an internal competition in resource allocation.

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

Abstract: • 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.

Effect of severe thermal treatment on spruce and beech wood lignins.

Abstract: • The structure, proportion and mode of assembly of lignin, celluloses and hemicelluloses have marked effects on the reaction mechanisms during thermal treatment and therefore have a strong influence on the quality of the final product. The effect of treatment conditions, including severe conditions (up to 553 K) and treatment duration (up to 8 h) on the structure of native spruce and beech lignins was studied. • Lignin content was determined by the Klason method and lignin structure was evaluated by thioacidolysis. • The results highlighted the strong reactivity of the native spruce and beech lignins towards severe heat treatments. The distinct susceptibility of syringyl (S) and guaiacyl (G) units towards thermal treatment is confirmed by comparing the data for beech and spruce samples. The most severe treatment of spruce wood (280 ◦ C) induced a dramatic enrichment in lignin content together with the almost complete disappearance of G lignin units, whereas a more moderate treatment substantially changed lignin structure by degradation reactions that affect the p-hydroxyphenyl (H) and G lignin units similarly. • Thioacidolysis revealed that the thermal treatment induces the appearance of vinyl ether structures in spruce lignins. The decreased yield of the G and S thioacidolysis monomers reflects the progressive disappearance of G and S lignin units only involved in β-O-4 bonds and the formation of condensed linkages in proportions related to treatment severity. In severe conditions, β-O-4 linked S units are more degraded than their G homologues.

The rise and fall of the black locust (Robinia pseudoacacia L.) in the “Siro Negri” Forest Reserve (Lombardy, Italy): lessons learned and future uncertainties

Abstract: • The alluvial forests of the Ticino valley have been greatly reduced in size and are now represented by only a small number of fragmented remnants. To study the natural development of the black locust, an invasive species, on relatively undisturbed lowland forests, two permanent plots were established in 2005 in the “Siro Negri” Forest Reserve. • The black locust became established almost exclusively between 1940 and 1960. The observed dynamic of the black locust in the Reserve was very similar to what has been observed in its native North American range: following the initial colonization, the black locust firmly established itself in the dominant and intermediate layers but did not regenerate. In addition to the absence of a significant younger population, the decline of the black locust is evident in an elevated mortality rate and higher proportion of black locust biomass in the total coarse woody debris (CWD) • Our results support the hypothesis that the best strategy to control the spread of black locust is to avoid disturbances that favour black locust colonization, and to wait for natural suppression of the species by other trees. Due to the lack of past reference conditions and the future uncertainties, ongoing monitoring will be needed to fully understand the dynamics of forest ecosystem change in the Reserve.

Very early selection for solid wood quality: screening for early winners.

Abstract: • This article reviews the theoretical basis for indirect selection – where early selection is an example – and how correlated response is calculated. • The review is followed by a description of issues as to the choice of selection criteria that could explain the lack of substantial progress on breeding for wood quality. These include: the autoregressive nature of selection criteria, overemphasizing the importance of basic density as selection criterion, ignoring age-related trends of wood properties, using rotation age rather than technical thresholds as objective traits and ignoring that not all grades have identical marginal economic value. • Three data sets are either analyzed for the first time or reanalyzed under different assumptions, to explore the importance of these criticisms. • Finally, the use of critical value thresholds as very early selection criteria is suggested and discussed in the context of improving intrinsic corewood quality.

Ectomycorrhizal fungus (Paxillus involutus) and hydrogels affect performance of Populus euphratica exposed to drought stress.

Abstract: • Mycorrhizal fungi and hydrogels (water-absorbing polymers) can improve water availability for trees. The combination of both factors for plant performance under water limitation has not yet been studied. • To investigate the influence of the ectomycorrhizal fungus Paxillus involutus, hydrogel and the combination of both factors, a drought-sensitive poplar, Populus euphratica, was examined in this study. • After 16 weeks of inoculation, no ectomycorrhizas were found. Nevertheless, P. involutusinoculated poplars displayed increased concentrations of soluble sugars and osmolality, leading to an improved water status. Growth was diminished compared with non-inoculated P. euphratica .T he presence of hydrogels in the rooting medium resulted in increased biomass and higher plant water content and decreased the osmolality of plant tissues. Drought markedly decreased water contents in rooting medium and plants, and leaf chlorophyll fluorescence, and stimulated the root growth, concentrations of soluble sugars and osmolality in plants. Under drought conditions, P. euphratica exhibited osmoregulation by accumulation of low-molecular-weight carbohydrates. • These data indicate that adding hydrogels to soils may improve the plant performance. The reasons for improved osmoregulation by fungi and hydrogels were probably related to their stimulating influence on the formation of soluble carbohydrates under drought conditions. Mots-cles : secheresse / hydrogel / champignon mycorhizien / peuplier / hydrates de carbone

Effects of atmospheric and climate change at the timberline of the Central European Alps.

Abstract: • This review considers potential effects of atmospheric change and climate warming within the timberline ecotone of the Central European Alps. After focusing on the impacts of ozone (O3 )a nd rising atmospheric CO2 concentration, effects of climate warming on the carbon and water balance of timberline trees and forests will be outlined towards conclusions about changes in tree growth and treeline dynamics. • Presently, ambient ground-level O3 concentrations do not exert crucial stress on adult conifers at the timberline of the Central European Alps. In response to elevated atmospheric CO2 Larix decidua showed growth increase, whereas no such response was found in Pinus uncinata. Overall climate warming appears as the factor responsible for the observed growth stimulation of timberline trees. • Increased seedling re-establishment in the Central European Alps however, resulted from invasion into potential habitats rather than upward migration due to climate change, although seedlings will only reach tree size upon successful coupling with the atmosphere and thus loosing the beneficial microclimate of low stature vegetation. • In conclusion, future climate extremes are more likely than the gradual temperature increase to control treeline dynamics in the Central European Alps.

Species variables or environmental variables as indicators of forest biodiversity: a case study using saproxylic beetles in Maritime pine plantations

Abstract: • To assess the sustainability of plantation forest management we compare two types of biodiversity indicators. We used the species richness of saproxylic beetles as a case study to test the “species” and “environmental” indicator approaches. We compared single species abundance or occurrence and deadwood volume or diversity as predictor variables. • Beetles were sampled with flight interception traps in 40 Maritime pine plantation stands. The volume and diversity of deadwood was estimated with line intersect and plot sampling in the same stands. Predictive models of species richness were built with simple linear or Partial Least Square regressions. • Deadwood variables appeared to be good predictors of saproxylic beetle richness at the standscale with at least 75% of variance explained. Deadwood diversity variables consistently provided better predictive models than volume variables. The best environmental indicator was the diversity of deadwood elements larger than 15 cm in diameter. • By contrast, the use of “species variables” appeared to be less relevant. To reach the quality of prediction obtained with “environmental variables”, the abundance or occurrence of 6 to 7 species – some of which are difficult to identify – had to be used to build the indicator.

Modelling ozone fluxes to forests for risk assessment: status and prospects

Abstract: • Risk assessment of ozone effects on forests is gradually moving from concentration-based exposure metrics to a more complicated approach that requires modelling of ozone fluxes to trees. • This study reviews the status of the DO3SE stomatal flux model employed within the Convention on Long-range Transboundary Air Pollution, describing a range of applications and identifying major research needs, especially in the context of support that could be provided by the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests. • The most urgent development need for DO3SE is the modelling of the soil moisture status and its effect on stomatal conductance. Furthermore, the data related to the physical characteristics and the seasonal dynamics of physiological activity of vegetation continue to pose problems. • There is a clear need for more extensive validation of models and risk estimates using more rigorous statistical procedures and comparisons with flux networks and satellites. • The current large-scale forest monitoring activities provide only limited possibilities for flux modelling, but could be enhanced by introducing a new monitoring strategy outlined here.

Simplified and improved somatic embryogenesis of hybrid larches (Larix × eurolepis and Larix × marschlinsii). Perspectives for breeding

Abstract: • Development of clonal propagation method, such as somatic embryogenesis, has numerous applications such as mass-production of genetically improved plants and the amenability of embryogenic cultures to cryogenic storage. Since the 90’s, researchers at INRA have engaged in research on somatic embryogenesis in Larix species (Larix × eurolepis, Larix × marschlinsii). • The aim of this work was to improve and to simplify all steps of somatic embryogenesis and to apply this protocol to the new hybrid variety REVE-VERT. • The somatic embryogenesis initiation frequency from immature zygotic embryos was high (65%) on a medium with reduced plant growth regulator concentrations (2.2 µ Mo f 2.4-dichlorophenoxyacetic acid and 2.3µM of 6-benzyladenine). Simplified cryopreservation method (no need of programmable freezer) of the embryonal masses resulted in 100% recovery of cryopreserved lines. Maturation of a large number of somatic embryos was greatly improved when embryonal masses were dispersed on filter paper placed on medium containing high concentration of gellan gum (8 g·L −1 ). Under these conditions, 94% of the lines matured somatic embryos that developed into plantlets. Clearly ageing and cryopreservation did not reduce embryogenic potential of embryonal masses. • Requirements for the effective integration of somatic embryogenesis into the larch breeding programme are discussed.

A merchantable volume system for Pinus sylvestris L. in the major mountain ranges of Spain

Abstract: • Accurate estimation of stem volume makes it possible to estimate the monetary value of one of the many commodities and services that forests provide to society, i.e. timber. • In the present study a compatible volume system for Scots pine in the major mountain ranges of Spain (the Pyrenees, Southern Iberian Range, Northern Iberian Range, Soria and Burgos Mountains, Central Range and Galician Mountains) was developed with data from 2 682 destructively sampled trees. Several well-known taper functions were evaluated. A second-order continuous-time autoregressive error structure was used to correct the inherent autocorrelation in the hierarchical data, allowing the model to be applied to irregularly spaced and unbalanced data. • The compatible segmented model of Fang et al. (2000) best described the experimental data. It is therefore recommended for estimating diameter at a specific height, height to a specific diameter, merchantable volume, and total volume for the six mountain ranges analyzed. • The non-linear extra sum of squares method indicated differences in mountain range-specific taper functions. A different taper function should therefore be used for each mountain range in Spain.

Freezing injury in primary and secondary needles of Mediterranean pine species of contrasting ecological niches

Abstract: • Pine seedlings show a marked ontogenetic difference between primary and secondary needles, the latter prevailing with a different timing among species. • Using the electrolyte leakage method following an artificial freezing test, we aimed at (1) determining the differences in freezing tolerance between primary and secondary needles in eight pines of contrasting thermal habitats: P. canariensis, P. pinea, P. halepensis, P. brutia, P. pinaster, P. nigra, P. sylvestris and P. radiata, (2) evaluating the relation between freezing tolerance and sclerophylly and (3) relating freezing tolerance with the climate of origin. • Primary needles were significantly more sensitive to freezing than secondary needles in Pinus halepensis, P. brutia, P. pinaster and P. nigra, whereas no differences were found in P. canariensis, P. pinea and P. radiata. LT50 was uncorrelated with needle sclerophylly but very highly correlated with the mean temperature of the coldest month at the seed source. • Results support an adaptive role of secondary needles in the mountain Mediterranean pines P. nigra, P. pinaster and P. brutia, while the more complex responses in coastal Mediterranean pines can be interpreted in the light of seedling ontogeny and species’ ecological niches.

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

Abstract: Keywords: Tectona grandis / extractives / tectoquinone / desoxylapachol / tree age Abstract • 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 heart- wood 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 re- sistance parameters and the content of tectoquinone and isodesoxylapachol. Mots-cles : Tectona grandis / extractibles / tectoquinone / desoxylapachol / âge des arbres

Drought susceptibility and recovery of transplanted Quercus rubra seedlings in relation to root system morphology

Abstract: • Transplant shock, implicated by depressed seedling physiological status associated with moisture stress immediately following planting, limits early plantation establishment. Large root volume (Rv) has potential to alleviate transplant shock because of higher root growth potential and greater access to soil water. • We investigated impacts of drought and transplant Rv on photosynthetic assimilation (A), transpiration (E), stomatal conductance (gs), predawn leaf xylem water potential (ΨL), and growth of northern red oak (Quercus rubra L.) seedlings to explain mechanisms associated with susceptibility to transplant shock. One year-old barerooot seedlings were graded into four Rv categories and either well watered or subjected to drought consisting of low, medium, or high moisture stress by discontinuing irrigation at 22-day intervals for 3 months. Thereafter, all treatments were re-watered to examine recovery.

Establishment limitation of holm oak (Quercus ilex subsp ballota (Desf.) Samp.) in a Mediterranean savanna - forest ecosystem

Abstract: • Tree recruitment in Mediterranean savannas is generally hampered, in contrast with the original oak forests where these savannas are derived from. We asked whether this difference in recruitment success can be explained by differential post-dispersal survival. For one year we monitored experimentally cached holm oak acorns in a savanna — forest ecosystem in Central Spain, and recorded cache pilferage, type of pilferer, boar rooting, seedling emergence, seedling survival and the cause of mortality. • Cache pilferage was significantly lower in savanna (8%) than in forest (21%). However, the higher cache survival was more than offset by lower seedling emergence and, particularly, by nine times higher seedling mortality in savanna, mainly due to desiccation. Wild boar rooting did not differ between experimental caches and controls without acorns, indicating that individual cached acorns do not trigger rooting activity. • Our results indicate that the difference in post-dispersal survival between savanna and forest is due to lower emergence and, primarily, higher seedling mortality in savanna, not to higher cache pilferage. Absence of safe sites such as shrubs, abundantly present in the forest, may well explain the lack of recruitment in the savanna. Management measures appear necessary for long-term persistence of Mediterranean savannas in general.

Deforestation and forest degradation in Papua New Guinea

Abstract: • The Government of Papua New Guinea (PNG) has played a prominent part in recent negotiations for “rainforest nations” to be compensated for reducing greenhouse gas emissions from deforestation or forest degradation (DFD). • A new report “The State of the Forests of Papua New Guinea” claims that rates of DFD in PNG are much higher than have previously reported. It suggests more than half of PNG’s remaining forests will have disappeared or be damaged beyond recovery by 2021. • We argue that this claim is incorrect. The report overestimates the area of intact primary forest in 1972 and the impact of traditional land use practices on forest cover. Much of what the RSLUP report considers as deforestation is part of a cycle of traditional clearance for farming, fallow and regrowth that has been occurring for hundreds of years. • The assumption that areas impacted by harvesting or shifting cultivation will inevitably degrade and become non-forest is also not supported by observation of cutover forest in PNG. A considerable proportion of cutover forest areas will recover carbon stocks after harvesting. • It is argued that traditional land use practices and forest recovery processes need to be considered in assessing greenhouse gas emissions from deforestation and degradation in countries with complex land use histories such as PNG.

Phenotypic variation in the phenology of ascospore production between European populations of oak powdery mildew

Abstract: • Oak powdery mildew severity (Erysiphe alphitoides) is usually mild in Europe because epidemics start late in spring, at the end of the first oak growth unit maturation. However, the disease can occasionally be very severe when strong infection occurs early during the development of the first growth unit, suggesting that host-pathogen synchrony in spring could be a critical factor in disease severity. • We studied the timing of ascospore production in a given environment for four E. alphitoides populations sampled from SW France to the Czech Republic to determine whether this trait shows variation within Europe. • Timing of ascospore production was clearly influenced by environmental factors as chasmothecia from a single origin showed very different dates of optimal ascospore production when transferred for overwintering in locations with different climate. In common garden experiments, no differences were observed between populations for the date of optimal ascospore production. • Results suggest little genetic differentiation for timing of ascospore production for E. alphitoides populations across Europe and therefore a lack of local adaptation to their host phenology. Availability in ascospore inoculum is limited during host budburst, explaining the low infection usually observed on the first oak growth unit.

Temporal trends in the foliar nutritional status of the French, Walloon and Luxembourg broad-leaved plots of forest monitoring

Abstract: Two decades after the launching of the monitoring program of forest ecosystems in Europe (ICP forests), a unique data set is now available regarding the foliar nutritional status of the main broad-leaved species growing in much-diversified sites (soil, climate). This study focuses on the foliar concentration time series (1993 to 2005) of the French (RENECO-FOR), Walloon and Luxemburg broad-leaved plots. The aim is to show long-term trends while taking the inter-plot and inter-annual variability into account. Two kinds of statistical processing were used to analyze the data on foliar chemistry: principal component analysis (PCAs) and linear mixed models. In general, the main temporal trends reveal a decrease in the foliar P concentration and a decrease in the foliar Ca concentration, except for European beech on acid soils. These temporal patterns confirm the trends previously observed and could be explained by the joint actions of several processes that influence tree nutrition in the long term: tree age, N and S deposition, harvesting and climate.

High resolution temporal variation in wood properties in irrigated and non-irrigated Eucalyptus globulus

Abstract: • Environmental determinants of wood properties variation were examined in Eucalyptus globulus ,a globally important hardwood plantation species, in southern Tasmania, Australia. • Radial variation in wood properties, measured with the SilviScan system, were re-scaled from distance to time abscissa using stem radial growth data measured with dendrometers. With this re-scaled data it was possible to evaluate how water availability and temperature affected wood density, microfibril angle (MFA) and fibre and vessel transverse dimensions in irrigated and non-irrigated trees. • Wood density, fibre radial diameter and MFA were sensitive to water availability. Wood density increased and fibre radial diameter decreased in response to reduced water availability. When high water availability was maintained, wood density was negatively correlated with temperature. Together, temperature and soil matric potential explained about 60% of temporal variation in wood density variation. In contrast MFA was not related to temperature but decreased with increasing water stress. Slower growing trees also had lower MFA than faster growing trees. Slower growing trees had a larger number of vessels per unit area of wood than faster growing trees within this even aged stand. However, vessel radius to the 4th power was significantly higher in faster growing trees than in slower growing trees. • Overall, E. globulus wood properties were sensitive to temporal changes in environmental conditions (particularly water availability) and associated growth rates. The data provided support for the hypothesis that growth rates are hydraulically mediated.