Intraspecific trait variation is a keystone variable in evolutionary biology as it contains information on past adaptational processes as well as future evolutionary potential of species. Recently, intraspecific trait variation has become an important data source for various research disciplines such as species distribution modelling, eco-evolutionary research, gene-environment associations, tree breeding and many more. Yet, systematic and rangewide data for long-living organisms such as trees are rare. This is partly because only a few old experiments on intraspecific trait variation still exist in Europe. What is more, their data are often stored in non-digital format and are therefore hardly findable, accessible, interoperable and reusable. Here we present a provenance trial dataset aiming to fill this gap by compiling information on intraspecific trait variation for 10 European tree species together with necessary metadata on trial sites and provenance origin. In total, measurements from more than 1,900 provenances growing in 75 trial sites across Europe provide nearly 1 million observations on growth, phenology, survival, competition, fructification, resilience, and other important life history traits. This OptFORESTS provenance trial data base was prepared as part of the European HORIZON OptFORESTS project. It represents one of the largest datasets on phenotypic variation in trees that has been published to date in terms of number of species and provenances tested and is the first initiative aiming at compiling such data across European countries with open access .

Ash dieback (ADB) has been threatening populations of European ash ( Fraxinus excelsior & F. angustifolia) ) for more than three decades. Although much knowledge has been gathered in the recent past, practical conservation measures have been mostly implemented at local scale. Since range contraction in both ash species is likely to be exacerbated already in the near future by westward expansion of the emerald ash borer and climate change, systematic conservation frameworks need to be developed to avoid long-term population-genetic consequences and depletion of genomic diversity. In this article, we address the advantages and obstacles of conservation approaches aiming to conserve genetic diversity in situ or ex situ during tree pandemics. We are reviewing 47 studies which were published on ash dieback to unravel three important dimensions of ongoing conservation approaches or perceived conservation problems: i) conservation philosophy (i.e. natural selection, resistance breeding or genetic conservation), ii) the spatial scale (ecosystem, country, continent), and iii) the integration of genetic safety margins in conservation planning. Although nearly equal proportions of the reviewed studies mention breeding or active conservation as possible long-term solutions, only 17 % consider that additional threats exist which may further reduce genetic diversity in both ash species. We also identify and discuss several knowledge gaps and limitations which may have limited the initiation of conservation projects at national and international level so far. Finally, we demonstrate that there is not much time left for filling these gaps, because European-wide forest health monitoring data indicates a significant decline of ash populations in the last 5 years.

Hybrid aspen, a hybrid between the European aspen and North American trembling aspen (Populus tremula L. x P. tremuloides Michx.), is a promising species because of its fast-growth and its suitability for multi-purpose use. However, models for predicting the age-dependent development of stand characteristics are still missing. The main objectives of this study were therefore to develop the models for predicting stand characteristics of hybrid aspen plantations and to validate the model applicability. The target response variables were stand basal area (BA), basal area-weighted mean diameter (DG) and basal area-weighted mean height (HG). Data were obtained from clonal hybrid aspen trials in southern Finland and southern Sweden. Multivariate mixed-effects modelling was used to estimate the parameters of seemingly unrelated regression for BA, DG, and HG. Model fit provided the following predictor variables: stand age (AGE), the number of trees per hectare (TPH), site index (SI), growing degree-days (GDD5), soil and site type, and thinning treatment. The chosen predictors differed slightly by response variable, but all parameters were highly significant (P < 0.0001), and model goodness-of-fit statistics presented high accuracy: RMSE of 2.59 m2 ha-1 for BA, 1.21 cm for DG, 1.05 m for HG in arithmetic scale. The applied simulations illustrated clear differences in the predicted development of stand characteristics when input variables SI, TPH or GDD5 changed. The developed models were assessed to be easily applicable and useful for predicting the stand and tree characteristics of clonal hybrid aspen plantations, especially for the stands with AGE < 30 years and TPH < 2000 trees ha-1.

Production of applicable and homogeneous biochar for soil amendment purposes would benefit from knowledge on how feedstock heterogeneity impacts key biochar pore properties and how the properties are transformed due to pyrolysis. This study aimed (1) to quantify how clonal differences and within-tree heterogeneity of a hybrid aspen feedstock (wood) impact biochar pore properties and (2) to estimate how pore properties of non-pyrolysed wood materials are transformed when pyrolysed into biochar. The study was conducted by collecting samples from a hybrid aspen ( Populus tremula L. × Populus tremuloides Michx.) clonal field trial. Key pore properties of non-pyrolysed and pyrolysed wood samples were quantified with 3D X-ray imaging and quantitative image analyses. The results demonstrated how pyrolysis shifted distinctively bi-modal pore size distributions of the wood samples towards smaller pore size regions. The bi-modal wood tissue structure controlled the pore structure also in the biochars. Due to decreasing cell wall thicknesses, the pyrolysis increased the porosity of the materials. While the thermal process homogenized differences in the wall thicknesses, the thicknesses of the feedstock were also shown to control the resulting thicknesses in the biochars. Mechanisms of biochar pore property formation can be considered important when designing applicable biochars for a chosen purpose. Clonal differences and within-tree heterogeneity had a direct impact only on the wall thicknesses and the pore diameters of vessels. These impacts can be of interest when planning feedstock utilization in biochar production. However, the results suggest that relatively homogeneous biochar can be produced from hybrid aspen feedstocks.

This study was conducted to examine the characteristics of dominant height growth and develop site index models for clonal hybrid aspen plantations in southern Finland. Data were obtained from repeatedly measured clonal hybrid aspen trials with varying initial spacing: 2.5 m x 2.5 m (1600 trees ha(-1)), 3.0 m x 3.0 m (1200 trees ha(-1)), 3.5 m x 3.5 m (800 trees ha(-1)), and 5.0 m x 5.0 m (400 trees ha(-1)). The total number of data points in the analysis was 389 for the age of 3-20. Within the range of observed data, the dominant height grew linearly over age and was significantly different due to the initial planting density; growth was higher when the planting was denser. Using the initial density effect, dominant height growth models were developed based on the Chapman-Richards function through nonlinear mixed-effects modelling. The density variable was found to be statistically the best variable when modifying only the shape parameter of the Chapman-Richards function. All fixed-effects were significant for both models, with and without the density effect. The residual plots of the model did not show any bias over the predicted value, stand age or planting density. The predicted dominant height was higher with increasing initial density. The predicted dominant height increment was faster with higher planting densities until the age of 14 years. The anamorphic site index curves were presented with base age of 20 years including the planting density effect. The overall pattern of site index curves was consistent with those observed in previous studies. The models developed in this study can be used to estimate the dominant height and site index of hybrid aspen plantations in southern Finland.

ABSTRACT Vegetatively propagated hybrid aspen (Populus tremula × P. tremuloides) is one of the fastest growing tree species in Finland. To study clonal variation in element concentrations in wood, bark and branches, and the amount of elements bound in above-ground biomass, seven clones were selected from a field trial in Southern Finland, when the trees were 13 years old. Significant clonal differences in the growth and allocation of biomass in stem wood, stem bark and branches were found. On average, the biomass consisted of 56% of stem wood, 10% of stem bark and 34% of branches. The clone with the highest total biomass production also had the highest fraction of biomass allocated to branches (43%). The study also revealed significant clonal differences in the concentrations of most of the studied elements in wood, bark and branches, and in the amounts of elements bound in the leafless above-ground biomass. For most of the elements, the highest concentrations were found in the stem bark followed by branches. Hybrid aspen bark was especially rich in Ca compared to some other broad-leaved tree species. There were also significant clonal differences in the amount of heavy metals (Cd, Cu and Zn) bound in the biomass.

This study aims to promote comprehensive utilization of woody biomass by providing a knowledgebase on the utility of aspen bark as a new alternative source for fossil-based chemicals. The research focused on the analysis of clonal variation in: (1) major chemical components, i.e., hemicelluloses, cellulose, and lignin; (2) extraneous materials, i.e., bark extractives, and suberic acid; (3) condensed tannins content and composition; and (4) screening differences in antioxidative properties and total phenolic content of hot water extracts and ethanol-water extracts of hybrid aspen bark. Results of this study, the discovery of clonal variation in utilizable chemicals, pave the way for further research on added-value potential of under-utilized hybrid aspen and its bark. Clonal variation was found in notable part of chemicals with potential for utilization. Based on the results, an appropriate bark raw material can be selected for tailored processing, thus improving the resource efficiency. The results also indicate that by applying cascade processing concepts, bark chemical substances could be more efficiently utilized with more environmentally friendly methods.

Hybrid aspen (Populus tremula x P. tremuloides) is one of the fastest growing tree species in Finland. During the mid-1990s, a breeding programme was started with the aim of selecting clones that were superior in producing pulpwood. Hybrid aspen can also be grown as a short-rotation crop for bioenergy. To study clonal variation in wood and bark properties, seven clones were selected from a 12-year-old field trial located in southern Finland. From each clone, five trees were harvested and samples were taken from stem wood, stem bark and branches to determine basic density, effective heating value, moisture and ash content. Vertical within-tree variation in moisture content and basic density was also studied. The differences between clones were significant for almost all studied properties. For all studied properties there was a significant difference between wood and bark. Wood had lower ash content (0.5% vs. 3.9%), basic density (378 kg m(-3) vs. 450 kg m(-3)) and effective heating value (18.26 MJ kg(-1) vs. 19.24 MJ kg(-1)). but higher moisture content (55% vs. 49%) than bark. The values for branches were intermediate. These results suggest that the properties of hybrid aspen important for energy use could be improved by clonal selection. However, selecting clones based on fast growth only may be challenging since it may lead to a decrease in hybrid aspen wood density.

Hytönen J., Beuker E., Viherä-Aarnio A. (2018). Hybridihaavan kloonien välinen puun, kuoren ja oksien tiheyden, kosteuden ja lämpöarvon vaihtelu. Metsätieteen aikakauskirja 2018-9992. Tutkimusseloste. 3 s. https://doi.org/10.14214/ma.9992 Yhteystiedot 1Luonnonvarakeskus (Luke), Luonnonvarat, Kokkola; 2 Luonnonvarakeskus (Luke), Tuotantojärjestelmät, Savonlinna; 3 Luonnonvarakeskus (Luke), Tuotantojärjestelmät, Helsinki Sähköposti jyrki.hytonen@luke.fi Hyväksytty 18.04.2018 Seloste artikkelista Hytönen J., Beuker E., Viherä-Aarnio A. (2018). Clonal variation in basic density, moisture content and heating value of wood, bark and branches in hybrid aspen. Silva Fennica vol. 52 no. 2 article id 9938. https://doi.org/10.14214/sf.9938

In trees, the change from juvenile to adult vegetative phase can last for years. In Populus tremula L., this phase change is characterized by a morphological change in leaf shape, as leaves in the seedling phase typically are sharp-tipped, while saplings and trees have round-tipped leaves. In an open-field experiment, we studied the separate and combined effects of enhanced temperature and UVB radiation on 2-year-old P. tremula plantlets undergoing phase change. The concentration of salicylates was higher in the seedling-phase plants than in tree-type plants. In contrast, the concentration of condensed tannins was higher in the tree-type plants but only under ambient temperature. Enhanced temperature increased growth of the plants and the concentration of some salicylate compounds, and it decreased concentrations of flavonoids, phenolic acids, and condensed tannins. In addition, in the seedling-phase plants, the severity of rust infections decreased and herbivore damage increased under warming. The effects of enhanced UVB radiation were weaker, as concentrations of only two flavonoid compounds increased under enhanced UVB radiation. Based on our results, climate change may have a moderate delaying effect on the physiological development of both sexes of P. tremula, which may lead to lowered performance in their normal habitat in the future.

Changing climate is expected to cause range shifts and reduced growth in Norway spruce (Picea abies (L.) Karst). In order to mitigate these changes, genetic variation between populations can be utilized in selecting alternative tree origins that are better suited to the new conditions. The aim of this study was to examine the intraspecific differences in the climatic drivers of radial growth in Norway spruce. We used tree-ring data from seven Norway spruce provenance experiments in Finland, located in different climatic conditions and including a large variety of provenances. The annual ring-width indices were studied with hierarchical clustering, correlation analysis with climate variables, pointer year analysis and linear models to identify the provenance differences in growth variation and its climatic control, and compare them on a latitudinal gradient. The cluster analysis revealed patterns of provenance differences in growth variation: north European and central European provenances were grouped in separate clusters within sites, although with some exceptions. Largest provenance differences in climate-growth responses were found in relation to winter and spring temperatures. In the southern provenances warm winters were typically associated with faster growth whereas for the northern provenances the correlations varied from non-significant to negative. In addition, the pointer year analysis showed negative growth anomalies only in the southern provenances for years with exceptionally cold winters. These patterns may reflect the physiological differences between the provenances relating to, for example, cold tolerance and the timing of spring phenology. As the climate warming in Europe is predicted to be strongest during the winter months, acknowledging the intraspecific growth responses to climate in Norway spruce becomes increasingly important. (C) 2016 Elsevier B.V. All rights reserved.

Summary We studied the effect of climate warming on H eterobasidion root rot in boreal forests by measuring respiration activity of pure cultures of H eterobasidion parviporum in Norway spruce ( P icea abies ) sawdust and by linking these data to temperature data obtained from three spruce forests located along a north‐south transect stretching from northern G ermany to northern F inland. The pure cultures applied in this investigation were homokaryotic, but in a separate investigation, we found no significant difference between the activity of homo‐ and heterokaryotic isolates. We also found that the temperature response curves of growth and respiration rates of this fungus were similar and propose that respiration reflects the general activity of H . parviporum . The respiration data were scaled up to annual cumulative respiration activity using daily temperature measurements from soil and air in the spruce forest sites. The annual respiration activity of H . parviporum showed a linear relationship with the average annual air temperature. An increase in the annual air temperature by 5°C would raise the annual activity of H . parviporum in spruce roots in northern Finland, southern Finland and northern Germany by 91%, 53% and 40%, respectively. This increase remains below the predicted increase in forest growth in northern Finland but exceeds considerably the predictions for southern Finland. According to the previous literature, a number of other decay fungi show a similar activity response to temperature as H. parviporum, suggesting that this result can be generalized to decay fungi with similar ecological habits.

Vegetation-related response variables adopted in the ICP Forests are related to health, growth, phenology, and diversity. Their assessment and measurement is subject to errors, which need to be controlled and documented. To do this, data quality requirements (DQRs) and intercomparison exercises were implemented. During 2009 and 2010, 111–260 field crews took part in different exercises organized across Europe. Results revealed that, while for some variables (e.g., tree diameter, standing basal area, ozone injury, species diversity) DQRs were substantially achieved, problems still exist for other measurements/calculations (tree height, volume and increment, crown base height, crown symptoms identification and description). In some cases, achievement of DRQs was partly due to relaxed DQRs. While the recent progresses in Quality Assurance/Quality Control for field surveys are promising, further effort is necessary to sharpen DQRs, refine standard operating procedures, and reinforce training.