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Overall, this special issue aims to show how forest sector models may help decision making and provide useful insights, when it comes to climate change mitigation policies and their impact on forest sector.

International audience; This review compares the selection criteria, findings, and heterogeneity of systematic reviews with meta-analyses of cognitive outcomes among children considered very preterm at birth.

International audience; This paper considers the evaluation of the characteristics of the channel that arises in the context of cooperative broadcast in mobile ad-hoc networks (MANETs) with practical radios, and tackles the problem of detection with affordable frequency domain receivers. When multiple nodes use cooperative signalling to transmit a signal to a destination, their clock offsets, oscillator drifts, and non-negligible propagation delays yield an equivalent doubly-selective channel seen from any destination node's point-of-view. For demanding applications with high data rate requirements, this equivalent cooperative channel needs to be mitigated with physical layer signal processing. In the first part of the paper, statistical characteristics of the power-delay profile of the equivalent cooperative transmission channel are modelled to gain a better understanding of its behaviour. This preliminary analysis points out that equalization is required to successfully carry out cooperative broadcast. Next, conventional linear frequency domain equalizer (FDE) and a recently proposed non-linear FDE based on Bayesian inference, are considered for the equalization of the aforementioned channels. The detection performance of these receivers is evaluated in some critical channels which can jeopardize the robustness of the cooperative links, identified with the preliminary statistical analysis. Numerical results indicate that, non-linear but low-complexity frequency domain receivers are attractive solutions for cooperative broadcast, especially within high-data rate applications.

An original expectation propagation (EP) based message passing framework is introduced, wherein transmitted symbols are considered to belong to the multivariate white Gaussian distribution family. This approach allows deriving a novel class of single-tap frequency domain (FD) receivers with a quasi-linear computational complexity in block length, thanks to Fast-Fourier transform (FFT) based implementation. This framework is exposed in detail, through the design of a novel double-loop single-carrier frequency domain equalizer (SC-FDE), where self-iterations of the equalizer with the demapper, and turbo iterations with the decoder, provide numerous combinations for the performance and complexity trade-off. Furthermore, the flexibility of this framework is illustrated with the derivation of an overlap FDE, used for time-varying channel equalization, among others, and with the design of a FD multiple-input multiple-output (MIMO) detector, used for spatial multiplexing. Through these different receiver design problems, this framework is shown to improve the mitigation of inter-symbol, inter-block and multi-antenna interferences, compared to alternative single-tap FD structures of previous works. Thanks to finite-length and asymptotic analysis, supported by numerical results, the improvement brought by the proposed structures is assessed, and then completed by also accounting for computational costs., Comment: 15 pages, 15 figures, under review for IEEE Journal on Transactions on Communications

The increasing carbon dioxide (CO2) concentration in the atmosphere in combination with climatic changes throughout the last century are likely to have had a profound effect on the physiology of trees: altering the carbon and water fluxes passing through the stomatal pores. However, the magnitude and spatial patterns of such changes in natural forests remain highly uncertain. Here, stable carbon isotope ratios from a network of 35 tree-ring sites located across Europe are investigated to determine the intrinsic water-use efficiency (iWUE), the ratio of photosynthesis to stomatal conductance from 19012000. The results were compared with simulations of a dynamic vegetation model (LPX-Bern 1.0) that integrates numerous ecosystem and landatmosphere exchange processes in a theoretical framework. The spatial pattern of tree-ring derived iWUE of the investigated coniferous and deciduous species and the model results agreed significantly with a clear south-to-north gradient, as well as a general increase in iWUE over the 20th century. The magnitude of the iWUE increase was not spatially uniform, with the strongest increase observed and modelled for temperate forests in Central Europe, a region where summer soil-water availability decreased over the last century. We were able to demonstrate that the combined effects of increasing CO2 and climate change leading to soil drying have resulted in an accelerated increase of iWUE. These findings will help to reduce uncertainties in the land surface schemes of global climate models, where vegetationclimate feedbacks are currently still poorly constrained by observational data.

Peatlands are a major terrestrial carbon store and a persistent natural carbon sink during the Holocene, but there is considerable uncertainty over the fate of peatland carbon in a changing climate. It is generally assumed that higher temperatures will increase peat decay, causing a positive feedback to climate warming and contributing to the global positive carbon cycle feedback. Here we use a new extensive database of peat profiles across northern high latitudes to examine spatial and temporal patterns of carbon accumulation over the past millennium. Opposite to expectations, our results indicate a small negative carbon cycle feedback from past changes in the long-term accumulation rates of northern peatlands. Total carbon accumulated over the last 1000 yr is linearly related to contemporary growing season length and photosynthetically active radiation, suggesting that variability in net primary productivity is more important than decomposition in determining long-term carbon accumulation. Furthermore, northern peatland carbon sequestration rate declined over the climate transition from the Medieval Climate Anomaly (MCA) to the Little Ice Age (LIA), probably because of lower LIA temperatures combined with increased cloudiness suppressing net primary productivity. Other factors including changing moisture status, peatland distribution, fire, nitrogen deposition, permafrost thaw and methane emissions will also influence future peatland carbon cycle feedbacks, but our data suggest that the carbon sequestration rate could increase over many areas of northern peatlands in a warmer future.

Understanding the genetic basis of the timing of bud set, an important trait in conifers, is relevant for adaptation and forestry practice. In common garden experiments, both Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) show a latitudinal cline in the trait. We compared the regulation of their bud set biology by examining the expression of PsFTL2, a Pinus sylvestris homolog to PaFTL2, a FLOWERING LOCUS T/TERMINAL FLOWER 1 (FT/TFL1)-like gene, the expression levels of which have been found previously to be associated with the timing of bud set in Norway spruce. In a common garden study, we analyzed the relationship of bud phenology under natural and artificial photoperiods and the expression of PsFTL2 in a set of Scots pine populations from different latitudes. The expression of PsFTL2 increased in the needles preceding bud set and decreased during bud burst. In the northernmost population, even short night periods were efficient to trigger this expression, which also increased earlier under all photoperiodic regimes compared with the southern populations. Despite the different biology, with few limitations, the two conifers that diverged 140 million yr ago probably share an association of FTL2 with bud set, pointing to a common mechanism for the timing of growth cessation in conifers.

International audience; The rings on the cross-section of the branch of a tree show the number of its years, and the greater or smaller width of these rings show which years were wetter and which drier. They also show the direction in which the branch was turned, for the part that was turned towards the north grows thicker than that turned towards the south so that the centre of the stem is nearer to the bark that faces south than to that on the north side. " Leonardo da Vinci. Leonardo published his observations of stem asymmetry in his notes for a treatise on painting without any attempt at explanation. It must represent one of the earliest references to reaction wood in the literature, although there can be no doubt that carpenters and joiners had long been intuitively aware of its effects on the working and mechanical properties of timber. With the passage of time our understanding of why and how it is formed in the tree has increased, providing a scientific basis for folk knowledge, but despite extensive research, much remains to be explained. The last major work on this topic was the Magnum Opus of Timell (1986), which summarised current ideas on compression wood in gymnosperms. No equivalent work has, however, been produced dealing with tension wood, its counterpart in angiosperm dicotyledonous trees. This reflects to some extent the fact that hitherto, tension wood has been of less commercial importance, although this is now changing with the breeding and development of fast-growing temperate-hardwood species. This book is intended to bring the reader up-to-date with progress in research into reaction wood, particularly with reference to tension wood, but also the developments in compression wood research since the publication of Timell's definitive work.

International audience; The book is a fundamental reference source on reaction wood for wood scientists and technologists, plant biologists, silviculturists, forest ecologists, and anyone involved in the growing of trees and the processing of wood. It brings together our current understanding of all aspects of reaction wood, and is the first book to discuss both compression wood and tension wood.Trees produce reaction wood to maintain the vertical orientation of their stems and the optimum angle of each branch. They achieve this by laying down fibre cell walls in which differences in physical and chemical structure from those of normal fibres are expressed as differential stresses across the stem or branch. This process, while of obvious value for the survival of the tree, causes serious problems for the utilisation of timber. Timber derived from trees containing significant amounts of reaction wood is subject to dimensional instability on drying, causing twisting, bending and splitting. It is also difficult to work as timber, and for the pulp and paper industry the cost of removing the increased amount of lignin in compression wood is substantial. This has both practical and economic consequences for industry.Understanding the factors controlling reaction wood formation and its effect on wood structure is therefore fundamental to our understanding of the adaptation of trees to their environment and to the sustainable use of wood.The topics covered include:-Morphology, anatomy and ultrastructure of reaction wood-Cell-wall polymers in reaction wood and their biosynthesis-Changes in tree proteomes during reaction wood formation-The biomechanical action and biological functions of reaction wood- Physical and mechanical properties of reaction wood from the scale of cell walls to planks-The detection and characterisation of compression wood-Effects of reaction wood on the performance of wood and wood-based products- Commercial implications of reaction wood and the influence of forest management on its formation

Two finite element modelling approaches have been applied and compared to simulate direct shear tests of soils reinforced by roots. The "frictional behaviour" method used with solid elements predicted shear strength of the root-soil system 4.6-6.9% higher than that predicted with "embedded beam elements". This difference can be considered as negligible. Embedded beam elements were thus chosen to discretize digitized Maritime pine root systems in a tree anchorage model. Results exhibited contrasted mechanical responses when considering different root material properties.

International audience; A large database of invasive forest pathogens (IFPs) was developed to investigate the patterns and determinants of invasion in Europe. Detailed taxonomic and biological information on the invasive species was combined with country-specific data on land use, climate, and the time since invasion to identify the determinants of invasiveness, and to differentiate the class of environments which share territorial and climate features associated with a susceptibility to invasion. IFPs increased exponentially in the last four decades. Until 1919, IFPs already present moved across Europe. Then, new IFPs were introduced mainly from North America, and recently from Asia. Hybrid pathogens also appeared. Countries with a wider range of environments, higher human impact or international trade hosted more IFPs. Rainfall influenced the diffusion rates. Environmental conditions of the new and original ranges and systematic and ecological attributes affected invasiveness. Further spread of established IFPs is expected in countries that have experienced commercial isolation in the recent past. Densely populated countries with high environmental diversity may be the weakest links in attempts to prevent new arrivals. Tight coordination of actions against new arrivals is needed. Eradication seems impossible, and prevention seems the only reliable measure, although this will be difficult in the face of global mobility.

International audience

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METAGENE, a simulation tool based on finite loci approaches: new developments to consider phenotypic plasticity in forest tree breeding. Final Conference Noveltree project "Tree Breeding, Genomics and Evolutionary Biology"

Special Section on Heterogeneity and University-Industry Relations.-- et al., This paper provides a new and systematic characterization of 488 universities, from 11 European countries: Finland, France, Germany, Hungary, Italy, Netherlands, Norway, Portugal, Spain, Switzerland and UK. Using micro indicators built on the integrated Aquameth database, we characterize the European university landscape according to the following dimensions: history/foundation of university, dynamics of growth, specialization pattern, subject mix, funding composition, offer profile and productivity. © 2010 Elsevier B.V. All rights reserved., Funding support by the European Commission through the PRIME Network of Excellence – Aquameth project (coordinated by Andrea Bonaccorsi and Cinzia Daraio) is gratefully acknowledged.

International audience; Investigating the many internal feedbacks within the climate system is a vital component of the effort to quantify the full effects of future anthropogenic climate change. The stomatal apertures of plants tend to close and decrease in number under elevated CO2 concentrations, increasing water use efficiency and reducing canopy evapotranspiration. Experimental and modelling studies reveal huge variations in these changes such that the warming associated with reduced evapotranspiration (known as physiological forcing) is neither well understood or constrained. Palaeo-observations of changes in stomatal response and plant water use efficiency under rising CO2 might be used to better understand the processes underlying the physiological forcing feedback and to link measured changes in plant water use efficiency to a specific physiological change in stomata. Here we use time series of tree ring δ13C (Pinus sylvestris) and subfossil leaf (Betula nana) measurements of stomatal density and geometry to derive records of changes in intrinsic water use efficiency and maximum stomatal conductance in the Boreal zone of northern Finland and Sweden. We investigate the rate of change in both proxies, over the recent past. The two independent lines of evidence from these two different Boreal species indicate increased intrinsic water use efficiency and reduced maximum stomatal conductance of similar magnitude from pre-industrial times (ca. AD 1850) to around AD 1970. After this maximum stomatal conductance continues to decrease to AD 2000 in B. nana but intrinsic water use efficiency in i>P. sylvestris reaches a plateau. We suggest that northern boreal i>P. sylvestris might have reached a threshold in its ability to increase water use efficiency and we discuss the implication for modelling stomatal conductance in the land surface schemes of General Circulation Models.

Pristine peatlands are carbon (C) accumulating wetland ecosystems sustained by a high water level (WL) and consequent anoxia that slows down decomposition. Persistent WL drawdown as a response to climate and/or land-use change directly affects decomposition: increased oxygenation stimulates decomposition of the old C (peat) sequestered under prior anoxic conditions. Responses of the new C (plant litter) in terms of quality, production and decomposability, and the consequences for the whole C cycle of peatlands are not fully understood. WL drawdown induces changes in plant community resulting in shift in dominance from Sphagnum and graminoids to shrubs and trees. There is increasing evidence that the indirect effects of WL drawdown via the changes in plant communities will have more impact on the ecosystem C cycling than any direct effects. The aim of this study is to disentangle the direct and indirect effects of WL drawdown on the new C by measuring the relative importance of 1) environmental parameters (WL depth, temperature, soil chemistry) and 2) plant community composition on litter production, microbial activity, litter decomposition rates and, consequently, on the C accumulation. This information is crucial for modelling C cycle under changing climate and/or land-use. The effects of WL drawdown were tested in a large-scale experiment with manipulated WL at two time scales and three nutrient regimes. Furthermore, the effect of climate on litter decomposability was tested along a north-south gradient. Additionally, a novel method for estimating litter chemical quality and decomposability was explored by combining Near infrared spectroscopy with multivariate modelling. WL drawdown had direct effects on litter quality, microbial community composition and activity and litter decomposition rates. However, the direct effects of WL drawdown were overruled by the indirect effects via changes in litter type composition and production. Short-term (years) responses to WL drawdown were small. In long-term (decades), dramatically increased litter inputs resulted in large accumulation of organic matter in spite of increased decomposition rates. Further, the quality of the accumulated matter greatly changed from that accumulated in pristine conditions. The response of a peatland ecosystem to persistent WL drawdown was more pronounced at sites with more nutrients. The study demonstrates that the shift in vegetation composition as a response to climate and/or land-use change is the main factor affecting peatland ecosystem C cycle and thus dynamic vegetation is a necessity in any models applied for estimating responses of C fluxes to changes in the environment. The time scale for vegetation changes caused by hydrological changes needs to extend to decades. This study provides grouping of litter types (plant species and part) into functional types based on their chemical quality and/or decomposability that the models could utilize. Further, the results clearly show a drop in soil temperature as a response to WL drawdown when an initially open peatland converts into a forest ecosystem, which has not yet been considered in the existing models. Luonnontilaiset suot ovat hiiltä sitovia ekosysteemejä. Niissä maaperän märkyydestä johtuva hapen niukkuus hidastaa orgaanisen aineen hajotusta. Ilmaston tai maankäytön muutos voi aiheuttaa suon pitkäkestoisen kuivumisen. Se vaikuttaa sekä suorasti että epäsuorasti hajotukseen ja sitä kautta hiilen kiertoon ja hiilitaseeseen. Merkittävin suora vaikutus on maaperän hapekkuuden lisääntyminen, mikä nopeuttaa hajotusta. Epäsuorasti kuivuminen vaikuttaa muuttamalla suon kasviyhteisöä: tyypillisten suokasvien, kuten rahkasammalten ja sarojen, biomassa, tuotos ja karikesyöte vähenevät, kun taas varpujen ja puiden lisääntyvät. Kasviyhteisössä ja sen karikesyötteessä tapahtuvilla muutoksilla voi olla suurempi vaikutus hiilen kiertoon kuin vedenpinnan alenemisella sinänsä. Näiden muutosten suuntaa ja merkitystä koko ekosysteemin hiilitaseelle ei kuitenkaan vielä tunneta riittävästi. Tässä työssä tarkasteltiin vedenpinnan tason vaikutusta suohon tulevan karikkeen määrään, kemiallisiin ominaisuuksiin, mikrobiaktiivisuuteen ja hajoamisnopeuteen, ja näiden lopputulemana tapahtuvaan uuden orgaanisen aineen kertymään. Kuivumisen suorien ja epäsuorien vaikutusten merkitystä arvioitiin vertailemalla ympäristötekijöiden (vedenpinnan taso sekä maan lämpötila ja kemialliset ominaisuudet) ja kasvillisuuden koostumuksen selitysvoimaa. Tätä tietoa tarvitaan, kun mallinnetaan soiden hiilen kiertoa muuttuvissa olosuhteissa. Lyhyt- (muutamia vuosia) ja pitkäkestoisen (muutamia vuosikymmeniä) kuivumisen vaikutuksia tutkittiin kolmella eri ravinteisuustasolla. Ilmaston vaikutusta arvioitiin lisäksi vertailemalla Pohjois- ja Etelä-Suomessa sekä Virossa sijaitsevia koealoja. Karikkeen kemiallisen koostumuksen ja hajotettavuuden arviointiin kokeiltiin perinteisten uuttomenetelmien ja regressiomallien lisäksi nopeaa ja edullista infrapunaspektroskopiaa ja monimuuttuja-analyysiä. Vedenpinnan aleneminen vaikutti kasvilajitasolla karikkeen laatuun, kariketta hajottavaan mikrobiyhteisöön ja karikkeen hajoamisnopeuteen. Nämä kuivumisen suorat vaikutukset olivat kuitenkin vähäisiä verrattuina karikkeen määrän ja koostumuksen muutosten epäsuoriin vaikutuksiin. Lyhytkestoisen kuivumisen vaikutukset tutkittuihin tunnuksiin olivat kaikkinensa melko vähäisiä. Pitkäkestoisen kuivumisen aikana karikesyöte kasvoi merkittävästi. Se johti orgaanisen aineen kertymän lisääntymiseen, vaikka hajotus samalla nopeutui. Kertyvän aineen laatu myös poikkesi selvästi luonnontilaisten soiden kertymän laadusta. Vaste vedenpinnan alenemiseen sekä nopeutui että voimistui suon ravinteisuustason noustessa. Tulokset osoittavat, että metsäojituksesta ja ilmaston kuivumisesta aiheutuvat muutokset soiden kasviyhteisöissä vaikuttavat oleellisesti hiilen kiertoon. Siksi kasvillisuusmuutokset on sisällytettävä malleihin, joilla arvioidaan hiilivirtojen vasteita muuttuviin olosuhteisiin. Muutokset on myös huomioitava riittävän pitkällä aikajänteellä. Työssä esitetään karikkeen kemiallisiin ominaisuuksiin ja hajoamisnopeuteen perustuvat soille tyypillisten kasvien toiminnalliset ryhmät, joita malleissa voidaan hyödyntää. Lisäksi työ osoittaa kuivumisen alentavan maan lämpötilaa huomattavasti, mitä malleissa ei ole otettu huomioon.

International audience; Hantaviruses belong to the Bunyaviridae family. While usually hosted by wild mammals, they are potentially pathogenic for humans, and several serologically distinct groups associated with different syndromes have been identified. Yet, investigations have mostly been conducted where human infections by hantaviruses constitute a real and well-identified public health problem, i.e., the holarctic and neotropical areas. Some hantaviruses have also been described from a Suncus murinus in India and a Bandicota indica in Thailand. In addition, recent investigations in Cambodia revealed new Hantavirus types. More recently, two new Hantavirus species were described: Sangassou from a Hylomyscus simus, and Tanganya from a Crocidura theresae, both from Africa (Guinea), thus strongly questioning the current views about geographic range, evolution, and epidemiology of hantaviruses. In such a framework, we have conducted a survey of Hantavirus diversity in Southeast Asia which allows us to isolate the Thailand virus and address questions about the taxonomy of their rodent hosts. Here we present a molecular analysis of representatives of all currently known Hantavirus species, thus allowing the comparison between the newly described ones with a large range sample of rodent hantaviruses. Our results clearly point to the presence of a particular lineage of hantaviruses in Southeast Asia. It also strongly suggests that new viruses, additional mammalian hosts and different related syndromes in humans are likely to be discovered in the near future, particularly in Southeast Asia and in Africa, where Muridae rodents are highly diversified. Furthermore, additional work is also urgently needed to investigate the hantaviruses associated with Crociduridae and Soricidae.

Two different types of sampler were used for the collection of humic-rich porewaters from ombrotrophic bogs at background and contaminated sites: a syringe-type sampler, which required manual filtration and dialysis chambers (peepers) where samples were filtered in situ. Concentrations of 10 trace elements Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, V and Zn have been determined in the collected porewater samples using inductively coupled plasma-sector-field-mass spectrometry. The accuracy of the analytical procedures was evaluated by the regular analyses of the two certified riverine water reference materials SLRS-2 and SLRS-4, respectively. For the syringe-type sampler, four different 0.45 μm syringe filters were tested. Low blank values together with sufficiently low filtration artefacts were obtained using unwashed GD/XP filters (Whatman). When pre-cleaned filters were used, Cu and Mo showed strong filtration artefacts. Mean metal concentrations of filtrates differed by up to five times, depending on the filter type used. Overall blank values of the sampling devices were as follows (ng l-1): Cd 1, Co 9, Cr 50, Cu 70, Mn 200, Mo 20, Ni 100, Pb 4, V 10, Zn 1000. The contribution of atmospheric dust during the on-site filtration might have enhanced overall blank levels of Cr, Cu and Zn when protective covers were not used during sample collection/on-site filtration. Metal concentrations at background sites were at ng l-1 levels except for Zn and Mn (low μg l-1). With the exception of Co and Mn, dialysis chambers were not suitable for sampling porewaters at these concentration levels. © 2005 Elsevier B.V. All rights reserved.

The structure and the mechanical properties of wood of Norway spruce (Picea abies [L.] Karst.) were studied using small samples from Finland and Sweden. X-ray diffraction (XRD) was used to determine the orientation of cellulose microfibrils (microfibril angle, MFA), the dimensions of cellulose crystallites and the average shape of the cell cross-section. X-ray attenuation and x-ray fluorescence measurements were used to study the chemical composition and the trace element content. Tensile testing with in situ XRD was used to characterise the mechanical properties of wood and the deformation of crystalline cellulose within the wood cell walls. Cellulose crystallites were found to be 192 284 Å long and 28.9 33.4 Å wide in chemically untreated wood and they were longer and wider in mature wood than in juvenile wood. The MFA distribution of individual Norway spruce tracheids and larger samples was asymmetric. In individual cell walls, the mean MFA was 19 30 degrees, while the mode of the MFA distribution was 7 21 degrees. Both the mean MFA and the mode of the MFA distribution decreased as a function of the annual ring. Tangential cell walls exhibited smaller mean MFA and mode of the MFA distribution than radial cell walls. Maceration of wood material caused narrowing of the MFA distribution and removed contributions observed at around 90 degrees. In wood of both untreated and fertilised trees, the average shape of the cell cross-section changed from circular via ambiguous to rectangular as the cambial age increased. The average shape of the cell cross-section and the MFA distribution did not change as a result of fertilisation. The mass absorption coefficient for x-rays was higher in wood of fertilised trees than in that of untreated trees and wood of fertilised trees contained more of the elements S, Cl, and K, but a smaller amount of Mn. Cellulose crystallites were longer in wood of fertilised trees than in that of untreated trees. Kraft cooking caused widening and shortening of the cellulose crystallites. Tensile tests parallel to the cells showed that if the mean MFA is initially around 10 degrees or smaller, no systematic changes occur in the MFA distribution due to strain. The role of mean MFA in defining the tensile strength or the modulus of elasticity of wood was not as dominant as that reported earlier. Crystalline cellulose elongated much less than the entire samples. The Poisson ratio νca of crystalline cellulose in Norway spruce wood was shown to be largely dependent on the surroundings of crystalline cellulose in the cell wall, varying between -1.2 and 0.8. The Poisson ratio was negative in kraft cooked wood and positive in chemically untreated wood. In chemically untreated wood, νca was larger in mature wood and in latewood compared to juvenile wood and earlywood. Tausta Puulla on aina ollut suuri merkitys suomalaisille, asumusten ja tarve-esineiden raaka-aineesta puu- ja paperiteollisuuteen. Puun tehokas hyödyntäminen edellyttää tietoa puun rakenteen kasvumekanismeista, yhteyksistä rakenteen muodostumisen ja ympäristöolosuhteiden välillä ja yhteyksistä rakenteen ja käyttöominaisuuksien välillä. On tärkeää tuntea esimerkiksi lannoituksen vaikutus puun rakenteeseen, jotta voidaan arvioida mitä lannoitetusta puusta kannattaa valmistaa. Käytettäessä puuta rakennusmateriaalina on hyvä tietää, minkälaiset ovat lujuusominaisuudet nuorpuussa lähellä ydintä tai pintapuussa lähellä kuorta. Kattavan tiedon saamiseksi täytyy tutkimus ulottaa soluseinien rakenteeseen asti. Soluseinän rakenneyksiköiden välisten vuorovaikutusten tuntemus auttaa ymmärtämään, miksi puusolujen rakenne on juuri sellainen kuin on, ja miten puun tilavuuden ja massan vuosittainen kasvu heijastuu kulloinkin muodostuvien soluseinien rakenteeseen. Tutkimusaineisto ja -menetelmät Työssä tutkittiin kasvuolosuhteiden ja jälsisolukon iän vaikutusta Suomessa tai Ruotsissa kasvaneen kuusen (Picea abies [L.] Karst.) solukon rakenteeseen ja etsittiin yhteyksiä rakenteen ja mekaanisten ominaisuuksien välillä. Menetelminä käytettiin röntgensäteilyn diffraktiota ja absorptiota, röntgenfluoresenssianalyysiä, optista mikroskopiaa ja vetokokeita solujen pituussuunnassa. Mittaukset suoritettiin Helsingin yliopistossa, Metsäntutkimuslaitoksella, Kielin yliopistossa sekä synkrotronisäteilylaboratorioissa Grenoblessa (European Synchrotron Radiation Facility ESRF) ja Hampurissa (Hamburger Synchrotronstrahlungslabor HASYLAB). Tulokset Selviä muutoksia havaittiin puusolukon ja soluseinien rakenteessa jälsisolukon iän kasvaessa ytimestä pintaan siirryttäessä. Kiteisen selluloosan muodostamat selluloosakristalliitit olivat keskimäärin pidempiä ja leveämpiä pintapuussa kuin nuorpuussa. Selluloosamikrofibrillien suuntajakauman keskiarvo ja moodi siirtyivät kohti solujen pitkittäissuuntaa jälsisolukon iän kasvaessa. Samanaikaisesti havaittiin solujen poikkileikkauksen muodon muuttuminen pyöreästä nelikulmaiseksi. Lannoituksella ei ollut vaikutusta mikrofibrillien suuntajakaumaan tai solujen poikkileikkauksen muotoon. Toisaalta puusolukon tiheys oli pienempi, alkuainekoostumus muuttui ja selluloosakristalliitit olivat pidempiä lannoituksen aikana muodostuneessa puussa. Vetokokeisiin yhdistetyt röntgendiffraktiomittaukset paljastivat monimutkaisen vuorovaikutuksen soluseinien selluloosamikrofibrillien ja niiden ympäristön välillä. Mikrofibrillien suuntajakauma ei systemaattisesti muuttunut venytyksen aikana eikä suuntajakauma suoraan selittänyt näytteiden murtolujuutta tai kimmomodulia. Sen sijaan solukon tiheydellä oli selvä vaikutus kemiallisesti käsittelemättömien näytteiden murtolujuuteen ja kimmomoduliin. Kemiallisesti käsittelemättömien näytteiden vetokokeissa selluloosakristalliittien selluloosaketjut venyivät ja samanaikaisesti niiden välimatka pieneni. Ligniinin poisto solukosta sulfaattikeitolla vaikutti tähän siten, että selluloosaketjujen venymisen ohella niiden välimatka kristalliiteissa kasvoi.