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This paper discusses Helmedag's article concerning Faustmann's formula (Helmedag in Eur J For Res, 2018. 10.1007/s10342-018-1101-8). He computed the present value of a fully regulated forest, including standing timber and theoretical land values. He showed that the optimal rotation in a fully regulated forest would always be the one that maximized the sustainable forest net revenues. Helmedag concluded that the discount rate would have no significance for the optimal rotation in a fully regulated forest, while his solution would still fulfil the optimality condition implied by Faustmann's formula. Here, we refute this assertion. In fact, the assumption of a fully regulated forest has no impact on the optimal rotation period, or may even reduce it. We illustrate this by appropriately considering the actual costs of achieving a fully regulated forest with altered rotation. One must not ignore the alterations of the financial flows when changing the underlying rotation age in an established fully regulated forest. When the opportunity costs of the transition period are included, the optimal rotation becomes the same as that of a single even-aged forest, or shorter, depending on the transition regime. Under the optimal transition regime, the diminishing marginal rate of return for extending the rotation period in a fully regulated forest matches the discount rate, when we achieve the Faustmann rotation. We conclude that the optimal rotation period is independent of the status as fully regulated forest, provided efficient harvest operations during the transition period. [ABSTRACT FROM AUTHOR]

In recent years, it has become increasingly popular to consider the forest-based industries as a so-called cluster. The forest cluster includes forestry enterprises as well as a wide range of industries, all engaged in the processing and manufacturing of roundwood as well as of semifinished and finished wood, pulp and paper products. The purpose of this paper was to depict the inter-industry linkages of the German forest cluster with the help of an input-output table. In the past, it was often the case that the various interactions between the different industries of the forest cluster were not fully perceived by industry managers, governmental bodies or associations, probably due to the distorted representation of the forest-based industries in official statistics. In this sense, the present study aimed at providing crucial baseline information for the understanding of this still rather fragmented sector. The disaggregated input-output table shows the various flows of inputs (measured in monetary values) into the productive process and matches them with outputs. Moreover, two exemplary impact analyses are conducted. [ABSTRACT FROM AUTHOR]

Coppicing is a form of forest management in European broadleaved forests. While it is still practised in south-eastern Europe, in central and western Europe it was almost completely replaced by high forest management. Currently, there are increasing efforts to reintroduce coppice management into former coppice woods. However, little comprehensive knowledge is available about the extent and management of coppice reintroduction and the processes governing it. In this paper, we present an overview of localities in the Czech Republic where coppice reintroduction was taking place in 2020. We identified 8 localities and conducted 10 semi-structured interviews with experts involved in their management in order to understand what motivated them to restart coppicing and what obstacles they have had to face. The main motivation of site managers is nature conservation, while the most important obstacles are operational issues, such as bureaucracy, complicated land ownership and legal responsibilities or lack of workforce. Other motivating factors identified in other European countries (production of a renewable energy source and potential for rural employment) have so far played a minor role in the Czech Republic. We conclude that a major challenge for future forest policies will be to utilise the economic experiences of regions with active coppicing to foster the spread of coppice woods in order to combine renewable energy production with biodiversity conservation. [ABSTRACT FROM AUTHOR]

In the twenty-first century, it is crucial to see climate change not only as a risk that can cause large-scale forest disturbances but also as an opportunity for innovative approaches to forest management and silviculture of new resistant tree species, like the prospective black pine (Pinus nigra J. F. Arnold). This literature review compiles findings from 260 scientific papers. It presents a summary of research results of black pine potential in European forests from 1970 to 2023. It describes the importance of its taxonomy, area of distribution and introduction, ecological characteristics, production, silviculture, wood quality, threats, and pests, as well as the potential of this tree species in relation to global climate change. In Europe, black pine covers an area of over 9.5 million ha and is one of the most frequently planted tree species outside of its original range. This pine is an effective tree species for afforestation management in arid habitats, as well as in areas threatened by pollution or on reclamation sites. Moreover, it resists the negative effects of climate change exceptionally well, such as more intense heat waves and more frequent long-term droughts, especially in young stands with lower tree density. However, the consequences of climate change on growth are not homogeneous across black pine distribution ranges due to interpopulation variability. It also has a high production potential advantage, and the wood is easy to process for various purposes. Overall, black pine can be considered one of the most adaptable pine species to anthropogenic factors and ongoing climate change, and a valuable tree species in forestry for newly cultivated areas in Europe. [ABSTRACT FROM AUTHOR]

The contradiction between ecological maintenance and economic production is increasingly prominent with the rapid development of forestry. Uncovering the forestry eco-efficiency which integrates ecology, resources and economic production is the premise of mitigating the hazards of strict reliance on heavy inputs and improving the resource utilization efficiency in forestry. This paper applies a three-stage data envelopment analysis (DEA) model combined with the DEA-Malmquist approach to eliminate the interferences of external environment and random errors and reveal the evolution of real forestry eco-efficiency and its decomposition. Besides, it is beneficial to understand the convergence of forestry eco-efficiency for grasping the long-term efficient operation mechanism of ecological production. The empirical results demonstrate that the forestry eco-efficiency progress is closely related to an excellent environment and efficient internal management by comparing the results between stage I and stage III. Different environmental variables have different effects on the slack of different inputs in stage II. Moreover, the convergence analysis proves the existence of absolute convergence and conditional convergence of forestry eco-efficiency in the whole China and six regions; that is, the catch-up effect is observed in backward provinces. Hence, targeted policy suggestions are provided to achieve forestry return to its green essence. [ABSTRACT FROM AUTHOR]

This paper is the first to examine both technical efficiency and scale elasticity of the forest sector across different European (EU) regions in an uncertain environment. In doing so, a dataset from 29 EU forest sectors have been collected; where the input and output data have been assumed to be random while their prices (or importance weights) were known. A chance-constrained data envelopment analysis approach was derived from several directional value-based models aimed at evaluating technical efficiency in the first stage. The results indicated that the number of efficient EU forest sectors were reduced substantially with extremely weak efficiency dispersion (about 18%), and the total average technical efficiency scores were moderately reduced by 0.74 as well. However, in the second stage, the findings of the modified cost/revenue-based scale elasticity model interestingly revealed that almost 7% of the EU forest sectors are in increasing returns to scale regions, which means they are still attractive acquisition targets and have the opportunity to increase the level of outputs and shift to the fully efficient border and finally increase their overall efficiency. As the major conclusion, all of our applied stochastic data envelopment analysis models (specially the cost/revenue-based approach) have high discriminating power in order to clearly distinguish the efficiency of the EU forest sector. [ABSTRACT FROM AUTHOR]

Although native to Australia, Eucalyptus species are found throughout Europe. At present, they are located mainly in the Iberian Peninsula and Eucalyptus globulus is the most commonly planted species. Climate forecasts anticipate an expansion of Eucalyptus to other regions of Europe. The fast growth of E. globulus, together with its resprouting ability and wood properties, has promoted the use of this species in the Iberian Peninsula. The total volume of E. globulus harvested there was close to 14 million m3 in 2019. Eucalyptus species represent the main source of raw material for the pulp and paper industries and provide an important source of income to non-industrial owners. Being exotic fast-growing trees, their expansion has also been associated with negative environmental impacts. The species therefore poses a series of challenges, while also generating opportunities. The objectives of this review paper are: (1) to summarize the importance of Eucalyptus plantations in Europe; (2) to analyse the opportunities and challenges of this genus in present and future plantations in Europe; (3) to assess to what extent forest management, at both stand and landscape levels, can reduce negative impacts; (4) to make policy and management recommendations that may support the use of this genus in other European regions. These aims are accomplished based on a thorough literature review, particularly focused on research developed in the Iberian Peninsula. [ABSTRACT FROM AUTHOR]

Pine plantations are an important wood source in Brazil, with Pinus taeda being most frequently planted. Most pinewood is directed to the paper and pulp industry, but there is an increasing demand for wood for solid end-uses, requiring large stems from longer rotations which can be obtained using P. taeda as the canopy in two-aged stands. We evaluated radial growth and wood density at different stem heights of P. taeda in the highlands of Southern Brazil over a production period of 36 years and subjected to shelterwood harvest. Cross-sectional disks were obtained from 15 trees in different stem heights; 10 were used for growth analyses and 5 for growth and density analyses. We used disk images and X-ray techniques for growth and density analyses, respectively. Samples were analyzed for ring (width and density), earlywood, and latewood (width, density, and proportion). Ring width varied between 0.4 and 1.7 cm, with the widest rings in the first years (3–5 years.) of growth. Ring density increased with age, with higher densities on the lower stem portions. Mature wood started to be formed from the 16th ring onwards. Shelterwood harvest affected both ring width and density, but the effects on ring width lasted for at least 5 years, while the effects on wood density were short-lasting. Mature P. taeda trees increased their size after the shelterwood harvest without compromising their wood density. Longer production periods of P. taeda as retained trees in the canopy of two-aged stands provide high-quality wood for structural purposes. [ABSTRACT FROM AUTHOR]

This paper aims to examine how the data envelopment analysis (DEA) technique can be applied to evaluate managerial ability and productivity growth for 29 European forest sectors over the period 2011–2020. Toward this end, we first applied DEA to evaluate the technical efficiency (TE) from both periodical-frontier and met-frontier perspectives in which results showed that the average TE was 0.645 and the annual operating efficiency of the years studied was reduced by 35%. A modified regression test is secondly developed in order to determine the effect of contextual variables on the log of TE. The findings showed that the regional density, time series and gross domestic product had the highest positive influence on improving the TE results, respectively. In the following, by considering the explanatory variables, a modified DEA-based Malmquist productivity index is used to calculate the productivity growth over the period 2011–2020. The results indicated that there was a decline of 12% for total factor productivity in 2019–2020 compared to 2014–2015 and 7% compared to 2015–2016 which is due to the uniform growth of technological change (TC) and efficiency change recession compared to previous periods. Hence, productivity growth is mainly due to frontier shift (TC). [ABSTRACT FROM AUTHOR]

The aim of this study was to measure and model the fuel consumption of cut-to-length (CTL) logging machinery in cutting and forwarding under Nordic harvesting conditions, and to clarify which factors had the greatest effect on the fuel consumption. In addition, the total annual fuel consumption and CO2eq emissions were calculated for CTL logging operations in Finland in 2020. The data were collected during a long-term follow-up study on the fuel consumption of harvesters and forwarders conducted between March 2018 and April 2019. The fuel consumption data were obtained from a total of 16 harvesters and 13 forwarders equipped with digital flow metres featuring an accuracy of ± 1% of the fuel volume measured. The engine power of the forest machines explained most of the hour-based fuel consumption. Correspondingly, the harvesting conditions of the forest stand best explained the cubic-metre-based fuel consumption. The fuel consumption of CTL logging operations (cutting and forwarding) averaged 1.4 L m−3 in final felling, and 3.1 and 2.2 L m−3 in first and later thinning, respectively. There was a large variation in the cubic-metre-based fuel consumption between individual machines, both for harvesters and forwarders. The total calculated fuel consumption in Finnish CTL operations in 2020 was 126.6 million L, with the calculated CO2eq emissions totalling 334,209 t (i.e. 5.7 kg m−3). Several measures to accelerate fuel and energy efficiency and reduce CO2eq emissions in CTL logging operations are discussed in the paper. [ABSTRACT FROM AUTHOR]

In the context of increasing heat periods and recurrence of droughts, and thus higher soil water depletion, we explored and quantified the role of understorey vegetation in ecosystem evapotranspiration in boreal and temperate forests. We reviewed and analysed about 200 papers that explicitly gave figures of understorey vegetation evapotranspiration relative to different stand features and traits. Understorey vegetation accounted on average for one-third of total ecosystem evapotranspiration during the growing season. Overstorey leaf area index (LAI) is the main variable that drives understorey evapotranspiration through radiation interception. Most data show that below an overstorey LAI of 2–3, the contribution of the understorey vegetation to ecosystem evapotranspiration increases exponentially, following the exponential increase of the climatic demand, i.e. potential evapotranspiration. Different factors have the potential to modulate this effect such as species composition and phenology, root distribution, and interaction with droughts. Consequently, managers must be aware that depending on understorey species present on site and stand structure, understorey vegetation can contribute significantly to a negative stand water balance. [ABSTRACT FROM AUTHOR]

How drought affects tree and stand growth is an old question, but is getting unprecedented relevance in view of climate change. Stress effects related to drought have been mostly studied at the individual tree level, mostly investigating dominant trees and using their responses as indicator for the impact at the stand level. However, findings at tree and stand level may differ, as the stand responses include interactions and feedbacks that may buffer or aggravate what is observed at the individual tree level. Here, we trace drought effects on growth and development from tree to the stand scale. Therefore, we analyse annually measured data from long-term experiments in temperate and Mediterranean forests. With this analysis, we aim to disclose how well results of dominant tree growth reflect stand-level behaviour, hypothesizing that drought resistance of dominant trees' can strongly deviate from the overall sensitivity of the stand. First, we theoretically derive how drought responses at the stand level emerge from the tree-level behaviour, thereby considering that potential drought resistance of individual trees is modulated by acclimation and tree–tree interactions at the stand level and that the overall stress response at the stand level results from species-specific and size-dependent individual tree growth and mortality. Second, reviewing respective peer-reviewed literature (24 papers) and complementing findings by own measurements (22 experiments) from temperate and Mediterranean monospecific and mixed-species forests, we are able to reveal main causes for deviations of tree-level and stand-level findings regarding drought stress responses. Using a long-term experiment in Norway spruce (Picea abies (L.) KARST.) and European beech (Fagus sylvatica L.), we provide evidence that the species-dependent and size-dependent reactions matter and how the size–frequency distribution affects the scaling. We show by examples that tree-level derived results may overestimate growth losses by 25%. Third, we investigate the development of the growth dominance coefficient based on measurements gathered at the Bavarian forest climate stations. We show that drought changes stand biomass partitioning in favour of small trees, reduce social differentiation, and homogenize the vertical structure of forests. Finally, we discuss the drought-related consequences of the social class-specific growth reaction patterns for inventory and monitoring and highlight the importance of these findings for understanding site-specific stand dynamics, for forest modelling, and for silvicultural management. [ABSTRACT FROM AUTHOR]

In commercial forest plantations dominated by Norway spruce (Picea abies L. Karst), the typically densely rooted forest floor and a poor understory contribute to the formation of surface or shallow hypodermic runoff, which limits the redistribution of infiltrated water to deeper soil layers. Pit-mound microrelief is a natural legacy in forest soils that originate from historical tree uprootings. This paper analyses the hydrological processes associated within the pit-mound microrelief based on the monitoring of soil electrical resistance (Rx). In two forested slopes, paired-tube profile probes were used to monitor the dynamics of Rx along four transects through pit-mound pairs at different soil depths. Cross-corelation analysis was used to detect the time-lag responses of deeper soil layers as compared to surface horizons within 15 pre-selected precipitation periods per site. Unlike other microsites, the Rx of deeper soil layers at pit microsites were mostly correlated to the Rx of surface horizons with a time lag of 0–6 h, demonstrating a fast redistribution of infiltrated water throughout the soil profile. Our results indicate that the pit-mound microrelief on forested slopes can positively contribute to the retention and redistribution of infiltrated water to the subsoil, not only through direct infiltration from the soil surface but also likely by the disruption and redirection of shallow lateral flow. Thereby, the pit-mound microrelief may facilitate groundwater recharge similarly as the technical measures that are currently used in arid and semiarid regions. [ABSTRACT FROM AUTHOR]

Determining the competitor selection methods for spatial explicit competition indices is important for individual tree growth modelling and forest management. There is a lack of systematic comparisons on these methods for natural mixed forest, however. In this paper, subplots with the area of 0.0625 ha were randomly sampled from 3 one-hectare remeasured and stem-mapped plots and repeated 200 times for natural spruce-fir-broadleaf mixed forests in northeast China with a bootstrapping method. Totally 600 subplots were used to examined the optimal competitor selection methods. Nine distance-dependent competition indices (CIs) and nine main competitor selection methods were tested by including them in the individual tree basal area growth models. After the analysis of the difference in the performance between partial model (only DBH was included) and full model (both DBH and CIs were included), we found that the difference among the statistically valid methods was weak (the increase in the adjusted coefficient of determination were 0.042 to 2.014%, the mean square errors were 0.060 to 2.851%). According to the magnitude and consistency of the contribution of the selection methods for a CI and the sensitivity to distinguish the competition effects on tree growth among the constituent tree species, we comprehensively concluded that the optimal competitor selection method was dependent on the CI, but the difference among these methods was weak. In addition, the CI from Alemdag (Alemdag IS (1978) Evaluation of some competition indexes for the prediction of diameter increment in planted white spruce. Information Report Forest Management Institute (Canada) No. FMR-X-108.) with the gradually expanding radius of circle method and 8 m radius of influence circle was the best combination which could efficiently detect the difference in competition effects on tree growth among tree species groups. [ABSTRACT FROM AUTHOR]

The lack of multi-dimensional data is one of the major gaps which limit the knowledge and the assessment possibilities of European forests. Nowadays, the most extensive and complete data on the European forest statuses are given by National Forest Inventories (NFIs) which provide information about the extent of forest's resources and their composition and structure. Traditionally, NFIs collect data related to trees, with a limited consideration of other habitat components, such as ground vegetation. This information which goes beyond the mere arboreal component is instead essential for a more complete forest biodiversity assessment. This paper is aimed at introducing the ICP Forests LI-BioDiv database which resulted from BioSoil Forest Biodiversity, a large collaborative European project. This database is organized as a multi-dimensional forest geodatabase that contains forest structure and vegetation records collected in 19 European countries in the period of 2005–2008. The data were acquired from 3311 geocoded plots where several different types of data were gathered: stand-level general information, tree-level data, deadwood, canopy closure and floristic composition. This paper is structured in order to: (1) give a clear overview of the raw data available in the database and to (2) present an elaboration of raw data to calculate simple plot-level forest variables (biomass, deadwood volume, alpha diversity). On the basis of the results we achieved, the LI-BioDiv database appears useful mainly for research purposes aimed at studying cross-relationships between multiple forest variables and not for an operative use for monitoring and assessing European forest. In particular, we hope that this contribution can stimulate scientists to carry out cross-analysis of the database for defining future forest biodiversity indicators that could be introduced into the field protocols of the NFIs in Europe. [ABSTRACT FROM AUTHOR]

As non-industrial private forest owners own a large share of forests in Europe, their management choices can largely affect the delivery of forest ecosystem services of different types: provisional, regulation and cultural. The literature is rich in studies exploring the delivery of both provisional services (timber or wood products) and cultural ones (recreation or amenity). However, fewer researches have addressed the delivery of regulation services like regulation of climate, carbon sequestration or preservation of habitats. The paper intends to contribute to this scarce literature with a Southern European case study. It analyses whether non-industrial private forest owners from an Italian alpine region would be willing to deliver additional (i.e. beyond legal requirements) quantities of regulation forest ecosystem services, whether they would do so with or without payment, and what affects such willingness. Three services are analysed: habitat improvement, soil conservation and carbon sequestration. Three multinomial logit models are estimated on a sample of 106 non-industrial forest owners. The results show, among others, that the willingness to deliver regulation forest ecosystem services is enhanced when the service impacts also on the property scale: this result concurs with the literature which shows that non-industrial private forest owners very often maximise not only their profit but also their overall utility by considering the self-consumption of services. The paper concludes by providing indications for targeting and tailoring active forest management policies focused on non-industrial forest owners of Italian alpine regions. [ABSTRACT FROM AUTHOR]

The leaf area index (LAI) is a crucial vegetation parameter that characterizes leaf sparsity and canopy structure, and the study of the spatial distribution pattern of the forest LAI and its environmental response can help to reveal the adaptive capacity of forest vegetation to climate change in semiarid areas. In this paper, a remote sensing inversion model of the LAI, which pertains to the forest ecosystem of Xinglong Mountain in the transition zone between the Qinghai‒Tibet Plateau and Loess Plateau, was established by combining an optical instrumentation method, a remote sensing inversion method, and a generalized additive model (GAM). The results showed that (1) the Meris terrestrial chlorophyll index (MTCI) linear regression model provided the greatest explanatory power for the LAI in the Xinglong Mountain forest, with R2 = 0.88 and RMSE = 0.32. (2) The LAI was influenced mainly by the altitude, slope, profile curvature, aspect, planform curvature, temperature, precipitation, and evapotranspiration. According to the single-factor GAM, altitude (R2 = 0.43) explained most of the total variation in the LAI, followed by precipitation (R2 = 0.36). According to the multifactor GAM, the above influencing factors could explain 84.2% of the total variation in the LAI, which was significant (P < 0.001). (3) Interaction analysis revealed that the LAI was significantly influenced by the interaction between topographic and meteorological factors (P < 0.001). It was revealed that the topography of Xinglong Mountain is fragmented, the vertical band spectrum of vegetation is notable, and the forest LAI exhibits high spatial heterogeneity under the interaction between topographic and meteorological factors, reflecting the environmental response mechanism of vegetation growth in forest ecosystems in ecological transition zones. [ABSTRACT FROM AUTHOR]

Recently, the connection between multispecies tree planting and the production of high-quality wood has received much attention. The branch diameter (BOD\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$BOD$$\end{document}) is a crucial factor that influences tree growth and wood quality. Research on BOD\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$BOD$$\end{document} in mixed plantations has lagged behind that on monocultures, where the effects of trees, stands, and competitive forces on the BOD\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$BOD$$\end{document} have been extensively studied. In this paper, 105 Manshurian ash (Fraxinus mandshurica Rupr.) and 105 Changbai larch (Larix olgensis Henry) trees from different row-wise mingling patterns on plantations in northeastern China were destructively sampled to construct two-level mixed-effects BOD\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$BOD$$\end{document} models. We examined how tree vigor and species mixture affect BOD\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$BOD$$\end{document} at various positions within the crown. The results showed that in addition to tree vigor, competition and stand structure had impacts on mixed plantation BOD\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$BOD$$\end{document}. Furthermore, in mixed plantations, the BOD\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$BOD$$\end{document} of Changbai larch was affected by intraspecific and interspecific competition, while that of Manshurian ash was affected only by intraspecific competition. The BOD\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$BOD$$\end{document} in the upper crown was strongly influenced by the position of the branches, while the BOD\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$BOD$$\end{document} in the lower crown was strongly influenced by tree vigor, competition, and stand structure. The introduction of a two-level mixed-effects model significantly improved the prediction accuracy of BOD\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$BOD$$\end{document}, for which the R2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${R}^{2}$$\end{document} values were 0.85 and 0.88 for Manshurian ash and Changbai larch, respectively. The size of branches is an important factor affecting wood properties and prices, and it is a variable that is important to control. The quantitative simulation of BOD\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$BOD$$\end{document} provides a theoretical basis that can inform silvicultural and management plans and that can determine the appropriate proportion of species based on actual timber quality requirements and stand development needs. [ABSTRACT FROM AUTHOR]

In Germany, Douglas fir (Pseudotsuga menziesii Franco) is seen as a valuable species for future cultivation in times of climate change. Local seed production in seed stands and seed orchards may secure that local adaptation is transferred to the next generation, but small population sizes could lower genetic diversity and thus future adaptability. Here we analyse the transfer of genetic diversity from parent to offspring generation in four older German seed orchards. We detected low pollen contamination rates due to high levels of spatial isolation. Even with a relatively low number of 40 clones, seed orchard design with randomized and repeated planting of clones led to low selfing rates, and despite uneven parental contributions, the number of successful parents and the level of genetic intermixture were high enough to allow the transfer of an adequate part of the genetic diversity to the next generation. Larger numbers, however, might be needed to reliably conserve the entire genetic diversity over succeeding generations. Conclusions on the establishment of future seed orchards and regarding areas requiring further research are drawn at the end of the paper. [ABSTRACT FROM AUTHOR]

As a generalization, harvested timber is extracted from forests either as trees or stems by skidders or as logs by forwarders. Coupled with harvesters, forwarders team up to form cut-to-length (CTL) systems that are often perceived to be more modern than full-tree (FT) and tree-length (TL) systems, based on feller bunchers and skidders. As a result, CTL machinery has been extensively studied in Europe, while little information is available on FT and TL machinery and especially skidders. Using all available documentation, and relying on national experts, this paper reports on a survey of skidders used for timber extraction in Europe. The survey identified a total of 8370 skidders, whereby the authors accept this to be a lower limit with potentially many other units not identified through the survey. Also, while the focus of the survey was purpose-built skidders, many modified farm tractors are also used to extract tree-length material. Of the 8370 skidders, 5500 were found in the Central European region with Germany and France dominating the market. The survey also indicated an overall low level of replacement, with fewer than 5% being from new sales annually. Although CTL systems are a dominant harvesting option, this survey has shown that skidders continue to be a common and viable extraction method. Given their high level of extraction efficiency that is often restricted by a limit of clear-fell operations, further large-scale damaging storm events in Europe may offer a clear opportunity for their expansion. [ABSTRACT FROM AUTHOR]

How plant–plant interactions will interact with global change drivers such as increased drought during the regeneration phase is a key question to forecast future vegetation dynamics. Chemical interaction and especially allelopathy and drought have been suggested to affect plant performance synergistically, i.e., that plant under drought stress would be more sensitive to allelochemicals and that exposure to allelopathic interactions could increase drought sensitivity through an inhibition of root development and mycorrhization. In this paper, we tested these hypotheses by using a controlled experiment with Quercus pubescens Mill. as a target species and three co-occurring species plus itself as source species. Allelopathic treatments consisted of annual provision of litter and monthly watering with green leaf aqueous extracts during two vegetation seasons starting from oak acorns. During the second vegetation season, a drought stress treatment was added on half of the seedlings. Allelopathy of co-occurring species reduced seedlings dimensions while Q. pubescens treatment increased it. During the second vegetation season, seedling growth rate and physiology were reduced by drought but poorly affected by allelopathic treatment. At the end of the experiment, drought stress and allelopathy from Cotinus coggygria and Pinus halepensis both reduced seedling biomass but had opposite effects on the root/shoot ratio. Drought and allelopathy did not interact significantly and, contrary to our hypothesis, there was a tendency of lower allelopathic effects under drought. Our results suggest that drought and allelopathy could additively alter seedling development, but the opposite effects of allelopathy and drought on the root/shoot ratio call for further experiments testing the interaction between these two factors. [ABSTRACT FROM AUTHOR]

Climate change modifies ecosystem processes directly through its effect on environmental conditions, but also indirectly by changing community composition. Theoretical studies and grassland experiments suggest that diversity may increase and stabilize communities' productivity over time. Few recent studies on forest ecosystems suggested the same pattern but with a larger variability between the results. In this paper, we aimed to test stabilizing diversity effect for two kinds of mixtures (Fagus sylvatica–Quercus pubescens and F. sylvatica–Abies alba), and to assess how climate may affect the patterns. We used tree ring data from forest plots triplets distributed along a latitudinal gradient across French Alps, adapting NBE approach to study temporal stability. We found that diversity effect on stability in productivity varies with stand composition. Most beech-fir stands showed a greater stability in productivity over time than monocultures, while beech-oak stands showed a less stable productivity. Considering nonadditive effects, no significant trends were found, regardless of the type of mixed stands considered. We further highlighted that these patterns could be partially explained by asynchrony between species responses (notably to variation in temperature or precipitation), overyielding and climatic conditions. We also showed that the intensity of the diversity effect on stability varies along the ecological gradient, consistently with the stress gradient hypothesis for beech in beech-oak forests, but not for beech-fir forests. This study showed the importance of the species identity on the relationships between diversity, climate and stability of forest productivity. Better depicting diversity and composition effects on forest ecosystem functioning appears to be crucial for forest managers to promote forest adaptation and maintain timber resource in the context of ongoing climate change. [ABSTRACT FROM AUTHOR]

In the recent decades, growing demand for wood products, combined with efforts to conserve natural forests, has supported a steady increase in the global extent of planted forests. In this paper, a two-phase sampling strategy for large-scale assessment of hybrid poplar plantations in Northern Italy was implemented. The first phase was performed by means of tessellation stratified sampling on high-resolution remotely sensed imagery, covering the survey area by a grid of regular polygons of equal size and randomly and independently selecting one point per quadrat. All the plantations spotted by at least one sample point were selected. In the second phase, we randomly chosen a subset of plantations by stratified sampling that were visited on the ground to collect qualitative and quantitative attributes. The resulting estimates were reliable, and the survey demonstrated relatively easy to be implemented and replicated. These considerations support the use of the proposed sampling strategy to frequently update information on fast-growing forest plantations within agricultural farms, like hybrid poplar crops. Moreover, the results of the case study here presented highlight the relevance of hybrid poplar plantations in Italy, in the context of sustainable development strategies under a green economy perspective. [ABSTRACT FROM AUTHOR]

Forest structures may be analyzed by considering both spatial and non-spatial aspects. These aspects are generally considered independently with little attention focusing on their association. However, the relationships between spatial and non-spatial structures may aid in explaining the characteristics of forests from various perspectives. In this paper, we analyzed the spatial structures of a mixed pine-oak forest with different-sized trees and the relationships among stand spatial structural parameters. This forest, located in the Nanpan River Basin in Southwest China, was in the early stage of succession. Our results showed that: (1) most species populations and trees of different sizes were nearly randomly distributed; (2) the degree of mixture gradually increased with an increase in individual plant size; (3) dominance increased with increasing individual size and could be well modeled by a negative exponential function; (4) there were no clear differences in mixture or distribution patterns among small-, medium- and large-sized trees in vertical layers, but large-sized trees were usually more dominant than small- and medium-sized trees; and (5) the distribution patterns of trees of different sizes had no association with species mixing or dominance, although there was a significant correlation between the degree of mixing and dominance. These findings indicate that tree size directly relates to the non-spatial structure of forests while also predicting their spatial structure characteristics accurately. [ABSTRACT FROM AUTHOR]

This paper explores the effects of three types of admixture treatments: (1) monospecific (M: European beech surrounded by six European beech seedlings), (2) single-admixture (S: European beech surrounded by six Norway spruce seedlings), and (3) group-admixture (G: European beech surrounded by three Norway spruce and three European beech seedlings), and two different CO2 concentrations ([CO2]): ambient [AMBCO2, 385 μmol (CO2) mol−1] and elevated [ELECO2, 770 μmol (CO2) mol−1] on the stem diameter increment (DI), based on a 7-year monitoring of the diameter growth of European beech (Fagus sylvatica L.) seedlings. Furthermore, to improve our understanding of the influence of climatic variables, we assessed the effects of precipitation and temperature on radial growth. After 7 years' experience (irrespective of admixture treatment), our data were not able to confirm the effect of elevated CO2 on the diameter growth (p value = 0.35), but the result was changed when the effect of elevated CO2 was considered under the different types of admixture. Elevated CO2 along with single-admixture increased the diameter increment significantly (p value = 0.001). In contrast, we characterized a significant effect of AMBCO2 × G interaction on DI (p value = 0.002). But DI was unaffected by elevated CO2 in M (p value = 0.77). In both [CO2], inter-specific competition with spruce resulted in the highest radial growth. The inter-specific interaction was most pronounced in the lower proportion with spruce (S) in ELECO2, while in ambient CO2, the higher proportion with spruce (G) had the greatest effect on the radial growth. With respect to the climatic factors, our observations showed that temperature had a stronger influence than precipitation in ELECO2, but in AMBCO2, precipitation had the strongest effect on the radial growth as indicated by the statistically significant correlation between climatic variables and radial growth. Overall, our result suggested that seedlings growth was more under the control of climate and edaphic factors than dependent on tree species diversity and CO2 concentrations. [ABSTRACT FROM AUTHOR]

In this paper, we first show both mathematically and empirically that the forest rent model is the wrong model to determine the optimal rotation age of a fully regulated forest as long as the standing timber has value. We then demonstrate that even if the forest is acquired for free, a fully regulated forest based on the forest rent model is actually worth more than the present value of its annual income. By converting to a fully regulated forest with a shorter rotation under the land expectation model, a higher present value of over 10% can be realized. [ABSTRACT FROM AUTHOR]

In this paper, the results of research on the variability of black alder cones (Alnus glutinosa L.) ware presented. The research was carried out for two, significantly different, batches of cones. Basic size parameters and mass were measured. The shape of the cone was determined, and it was described with the fourth-degree polynomial. The surface area and volume of the cone were calculated using the forming curve and formulas for solids: barrel and cylinder. The parameters of cones—shape surface area and volume—were analyzed. It was found that for alder cones (from the researched origins), the average volumes calculated from the barrel formula are 1701 mm3 and 1162 mm3, and the areas calculated from the cylinder formula are 807 mm2 and 597 mm2. The structure of the inner and outer sides of scales was examined using a scanning electron microscope. Using the MultiScanBase v. 18.03 program, the elements of husk structure that could affect the efficiency of seeds extraction were measured. The results of the research can be used to program the process of seeds extraction from alder cones in commercial installations. [ABSTRACT FROM AUTHOR]

Forest fires are expected to be more frequent and more intense with climate change, including in temperate and mountain forest ecosystems. In the Alps, forest vulnerability to fire resulting from interactions between climate, fuel types, vegetation structure and tree resistance to fire is little understood. This paper aims at identifying trends in the vulnerability of Alpine forest ecosystems to fire at different scales (tree species, stand level and biogeographic level) and according to three different climatic conditions (cold season, average summer and extremely dry summer). To explore Alpine forest vulnerability to fire, we used surface fuel measurements, forest inventory and fire weather data to simulate fire behaviour and ultimately post-fire tree mortality across 4438 forest plots in the French Alps. The results showed that cold season fires (about 50% of the fires in the French Alps) have a limited impact except on low-elevation forests of the Southern Alps (mainly Oak, Scots pine). In average summer conditions, mixed and broadleaved forests of low elevations suffer the highest mortality rates (up to 75% in coppices). Finally, summer fires occurring in extremely dry conditions promote high mortality across all forest communities. Lowest mortality rates were observed in high forest stands composed of tree species presenting adaptation to surface fires (e.g. thick bark, high canopy) such as Larch forests of the internal Alps. This study provides insights on the vulnerability of the main tree species and forest ecosystems of the French Alps useful for the adaptation of forest management practices to climate changes. [ABSTRACT FROM AUTHOR]

Foresters from many countries are seeking for tree species or provenances able to cope with expected climate change. While it becomes clear that some temperate tree species will increasingly suffer from climate warming, the fate of the ecologically and economically important silver fir (Abies alba Mill.) remains uncertain and debated because the ecological requirements of this species, as well as its resilience to drought, are still unclear. On the one hand, paleoecological studies reveal that this species was widely distributed under much warmer climate, suggesting a high potential to cope with ongoing and future climate warming. On the other hand, species distribution models generally predict a strong decline of its climatic suitability in the future. This paper aims to clarify the potential of this species to thrive in central and western Europe under predicted climate warming by reviewing the knowledge gained from different fields. Based on insight from different fields, we argue that silver fir has a great potential to thrive under warmer conditions in western and central Europe provided sufficient rainfall, as forecasted by climate models for most regions by 2100. For instance, dendroecological studies demonstrate that silver fir is more resistant and resilient to drought compared to co-occurring species such as Norway spruce, European beech and larch. The most prominent obstacle for increasing the proportion of fir in mixed forests nowadays is ungulate browsing that often prevents its upgrowth. [ABSTRACT FROM AUTHOR]

Allometric variations in tree height and stem diameter are a genetically controlled trait that reflects the ability of trees to adjust to different environmental conditions. This paper examines the ecological control of abiotic and forest-state variables on height- and stem diameter-growth in oriental beech (Fagus orientalis Lipsky) in an unmanaged, high-elevation forest of northern Iran. Spatially explicit abiotic variables of growing-season mean potential solar radiation, mean air temperature, topographic wetness index (TWI, as a proxy of soil water content) and wind velocity essential to the analysis were generated numerically by computer models. Forest-state variables of total tree height (H) and diameter at breast height (D) and stand basal area (BA) were assessed at individual sample plots. Degree of explanation of observed variation in individual-tree H and plot-level changes in stem D (i.e. dD/dt) by the assemblage of modelled abiotic and observed tree variables was 87.4%, with a root mean squared error (RMSE) and mean absolute error (MAE) of 3.60 and 2.84 m and 67.3%, RMSE = 0.13 cm and MAE = 0.10 cm, respectively. Wind velocity, TWI and mean air temperature provided the greatest overall influence on the calculation of static H and annual D-increment, with relative impact of 38.3, 37.3 and 9.6 and 7.7, 6.4 and 6.7, respectively. The other variables, including BA, had weak to no control on tree-growth response. Methods used here are sufficiently general to address tree-growth response in many other tree species around the world, with or without changes to site conditions. [ABSTRACT FROM AUTHOR]

This paper presents a psychological perspective to the selection of trees for urban residential areas. Sixty tree species suitable for urban planting sites were rated by lay participants regarding preference. We then used outward tree features to predict the preference ratings. Twenty-five different plant characteristics served as possible predictors in a regression model for tree preference. We found that the distinction between conifers and deciduous trees, the maximum tree height, and the crown height-to-width ratio were valuable predictors for preference, explaining more than 70% of the variance. This adds support for evolutionary theories of landscape preference. The regression model presented in this paper can be applied to calculate a preference estimate for other tree species using their known physical data, which may facilitate tree selection tasks in green space planning. By specifying preference-relevant tree characteristics, our findings may also inform the process of selecting diverse species for sites where a homogenous overall appearance is a planning goal. [ABSTRACT FROM AUTHOR]

One of the classic operations problems in forest management is to select the harvesting system and to plan the layout, which has a significant impact on overall operational and environmental efficiency. This paper addresses the design of a harvesting system in areas characterized by steep slopes requiring cable-based harvesting under central European conditions. We present two computationally efficient methods (designated as set-covering model SCM and bounded set-covering model BSCM) for solving problems of cable road layouts and comparing them with a previously developed model (CaMLOC). Formulating the problem as a type of location set-covering model allowed us to delineate a much smaller problem that was easier to solve. By applying the new model formulations, it is possible to identify mathematical optimal CR layouts for real-world forests areas up to 50 ha within a reasonable period of time and to even estimate the maximum gap in optimality (only with the BSCM approach). [ABSTRACT FROM AUTHOR]

This paper presents an ex-post calculation approach for the use-side estimation of wood fellings in Germany. Based on an existing approach for calculating wood removals, all roundwood using sectors and available data sources are to be identified. An intensive analysis and evaluation of the data scope and quality, as well as the subsequent identification of data gaps on the use side are essential parts of the approach. A complementary part of the study is the development of individual sectoral models to close the identified data gaps on the use side. The calculated data on wood removals are then used for the estimation of wood fellings, taking into account variables such as logging residues. The comparison of the use-side calculated data for fellings in this paper, with supply-based data from official statistics, shows that there was a difference of about 16.1 million m in 2013. This tendency toward constant underestimation of fellings in the official statistics is known from various studies and can now be quantified for the complete period of investigation (1995-2013). The results also allow for a more realistic view on a possible sustainable increase in wood harvests and on decision making in forest-based industries. Moreover, they allow for more accurate calculations of carbon sequestration in forests and harvested wood products. [ABSTRACT FROM AUTHOR]

Regenerating forest stands through natural seedlings is a commonly accepted silvicultural strategy in Germany. To plan for and increase natural regeneration within a given stand, foresters must be able to estimate whether the stand in its current state can produce sufficient saplings to replace the overstory. In this paper, we present two approaches to building a model that can estimate the probability of natural regeneration occurring, based on variables that are typically readily available from forest inventories. To estimate model parameters we used the large database of the third National Forest Inventory, which covers forest stands and sites across the whole of Germany, as well as weather and soil data. We examined how these variables impact the emergence of natural regeneration, ultimately fitting a model that can predict the occurrence of natural regeneration in 72% of cases. The influence of the variables on the predicted occurrence of natural regeneration was mixed, with most stand variables contributing only minor impact and most likely influencing natural regeneration via complex interactions. The exception was vertical structure (number of stand layers), which accounted for a large proportion of the goodness-of-fit of the model. An important finding was that forest ownership structure is a key variable for the prediction of the presence of regeneration. Data from this study support the assumption that some forest owners manage their stands in a way that fosters natural regeneration. [ABSTRACT FROM AUTHOR]

Bark wounds by damage during harvesting are a serious problem in forestry due to fungi infection and wood deterioration. This paper presents results of an investigation about the influence of the wounds on the internal structure of such injured stems. In an experiment, bark wounds were artificially created at the stem base of Norway spruce [ Picea abies (L.) Karst.] and silver fir ( Abies alba Mill.). 2 years later, the injured stems along with undamaged controls were cut and the trunk portion below breast height subjected to computer tomographic (CT) analysis. Analysis of the CT-images revealed a substantial impact of wounding on sapwood properties in spruce: directly adjacent to the wound surface in all examined trees, a large disturbance zone was detected affecting on average 17% of the potential sapwood area. With increasing distance from the wound, the size of this disturbance zone diminished, but was still detectable in all trees at breast height ca. 1 m above the bark wound. [ABSTRACT FROM AUTHOR]

Forests in Central Europe have been used since centuries and were systematically changed by silvicultural practices since the late 1700s. Focusing on possible biodiversity losses, forest stand management primarily impacts on the biodiversity attributes 'composition, structure and functioning' that are interlinked and incorporate different organizational and spatial ecosystem levels. Forest stand management can manipulate tree species diversity, which in turn affects stand structure and finally leads to changes in forest functions and services. We used meta-analyses to review 49 papers with 197 comparisons on compositional and structural diversity between unmanaged and managed forests as well as 53 comparisons of biomass productivity between mixed and monoculture forests throughout the temperate biome of Europe. Besides management impacts, for species and structural comparisons, we took time since abandonment of forest stand management into consideration when dealing with unmanaged forests. For species richness and diversity, we could not detect significant management effects; no significant influences of time since abandonment of management could be identified either. Structural attributes partly revealed considerable responses to forest stand management. Importantly, deadwood quantity, the number of microhabitats, and tree size diversity were reduced by forest stand management, while no effect was found for stand basal area and the number of living trees. Some of these effects become more pronounced with increasing time since abandonment. Forest productivity was significantly enhanced by regular moderate thinning compared with untreated stands and by tree species mixing compared with monospecific stands. Based on these results, we discuss the role of direct and indirect silvicultural effects, interactions between biodiversity components, the problem of defining the unmanaged reference state, and perspectives for forest stand management in practice. [ABSTRACT FROM AUTHOR]

Environmental services and landscape goods are rarely incorporated into economic valuation of natural resources, even though these resources may constitute a large proportion of the total ecosystem value, mainly in natural protected areas. The frequent occurrence of wildfires in Spanish protected areas requires a tool, which allows for the comprehensive management of landscape resource and mitigating the potential economic impacts caused by fire. In this paper, we extend the economic valuation theory to the concept of economic vulnerability. Geographic Information System was used to develop a framework for landscape impact assessment using annual landscape value, vegetation resilience and fire behavior. An economic approach of landscape susceptibility was provided by the integration of these three components. Once landscape susceptibility had been spatially characterized, landscape vulnerability was analyzed from criteria associated with landscape susceptibility and burn probability. There was a notable variation in landscape vulnerability ranging from 412,000 Euros to 1,200,000 Euros in Aracena Natural Park (186,828 ha) according to the selected contingent valuation scenario. The availability of cartography of landscape vulnerability could play a critical role in budget optimization and the decision-making process. In this sense, this approach helps managers to identify different efforts according to spatial distribution of the risk and fuel management strategies to increase economic efficiency of fire prevention activities. [ABSTRACT FROM AUTHOR]

This paper describes the development of a logistic model to predict the probability of surface fire spread in Brazilian rainforest fuels from outdoor experimental measurements. Surface fires spread over litter composed mostly of dead leaves and twigs. There were 72 individual outdoor experiments in eighteen sites. The fire propagated in 49% of the experiments. In each experiment, the litter height, litter temperature, unburned litter mass, wet and dry litter mass, soil temperature, wet and dry soil mass, ambient wind velocity, ambient air temperature, ambient air relative humidity and duration of fire spread were measured. Using these data, the rate of fire spread, litter bulk density, litter and soil moisture content, litter load and litter residue fraction were determined. For the sake of analysis, experimental results were classified into two groups: one for which the fire propagated and the other one for which the fire self-extinguished. Analyses of a logistic regression model showed that the relevant parameters for fire propagation are litter height and litter moisture content. Concerning the probability of successful fire propagation, the model showed a true positive rate of 71% and a true negative rate of 84%. The outdoor experiments also served to gather data to improve the understanding of surface fires and to provide input data for future computer simulations. [ABSTRACT FROM AUTHOR]

Climate change has increased the need of information on amount of forest biomass. The biomass and carbon storage for larch ( Larix spp.) in large geographic regions in China were failed to be accurately estimated from current biomass equations, because they were usually based on a few sample trees on local sites, generally incompatible to volume estimation, and not additive between components and total biomass. China needs reliable biomass estimation of the important species in the whole country. This study was based on the mensuration data of above- and belowground biomass from 600 and 198 destructive sample trees of larch from four regions in China, respectively. The main purpose was to develop compatible individual tree equations on both national and regional levels for above- and belowground biomass, biomass conversion factor and root-to-shoot ratio, using the nonlinear error-in-variable simultaneous equation approach. In addition, diameter at breast height ( D) and tree height ( H) growth models were also developed, and effects of key climate variables on biomass variation and growth process were analyzed. The results showed that mean prediction errors (MPEs) of regional aboveground biomass models were from 3.86 to 7.52%, and total relative errors (TREs) are within ±3%; and for regional belowground biomass equations, the MPEs are from 9.91 to 28.85%, and the TREs are within ±4%. The above- and belowground biomass and D- and H-growth were significantly related to mean annual temperature and mean annual precipitation. The biomass equations and growth models developed in this paper will provide good basis for estimating and predicting biomass of larch forests in China. [ABSTRACT FROM AUTHOR]

This paper presents new harmonized distance-independent individual tree basal area growth models for Norway spruce, Douglas-fir and Japanese larch in pure even-aged stands in Southern Belgium. The selected model was originally developed for Norway spruce and Douglas-fir in neighboring France. New formulations are proposed for some of the model components in order to lower the number of fitted parameters and facilitate the fitting procedure. The resulting models integrate the most recent corresponding top-height growth models and use four simple and usually collected explanatory variables: stand age, top-height, total basal area and tree girth at breast height. The modified formulations maintain similar fitting performances and make it easier to interpret the influence of the explanatory variables on tree growth. Parameters estimates were fitted on thousands of growth measurements gathered from several monitoring plots, forest management inventories and silvicultural field experiments that represent the wide range of site conditions and of forest management scenarios applied to coniferous stands in Southern Belgium. Cross-validation of the models revealed no bias and highlighted their consistent behavior over the entire range of girth at breast height, age, top-height, site index and density represented in our dataset. Combining utility and robust performances, these models represent useful forest management tools, purposely ideal for forest simulation software development. Moreover, the flexibility and generic capabilities of the model formulation should make it easily adjustable for other species in even-aged stands. [ABSTRACT FROM AUTHOR]

Populations of the internationally protected Black Stork Ciconia nigra in the northern parts of the distribution range, located to the east of the Baltic Sea, have suffered decline over recent decades. Since early 1990s, however, logging intensity has increased. In this paper, considering a ten-year period from the mid-1990s, we ask: (a) Did changes occur in the habitat preferred by Black Stork in the decade? (b) did the decade of intensified forestry significantly change forest characteristics? and (c) could the intensified forestry explain any observed changes in the utilization of habitat by storks? We compared forest characteristics at the beginning and end of this period at 75 random points and compared the habitat at 75 nest sites occupied by the Black Stork in the mid-1990s and 75 occupied nest sites at the end of the 2000s. In the 0.7-km zones around the random points, the abundance of mature stands decreased between the mid-1990s and the end of the 2000s, as did the abundance of broadleaved trees, but black alders increased. Nevertheless, the age and composition of tree species within the stands around the random points remained similar. Some changes were noted though in the habitat around nests used by Black Storks during two periods, with the data indicating that the Black Storks tended to occupy sites of better habitat quality (e.g. with a higher density of hydrological network and old oak trees, older nest stands) at the end of the 2000s than in the mid-1990s. Our results, however, do not support the idea that intensified forestry over the short term induced changes in the habitat used by the Black Storks. It is possible that nesting Black Storks became concentrated into the prime habitat when population retracted and/or abandoned habitat where recently recovered by the White-tailed Eagle. [ABSTRACT FROM AUTHOR]

The paper presents the results of experiments involving the exposure of Scots pine ( Pinus sylvestris L.) cones to microwave radiation. The pine cones were obtained from the Maskulińskie and Brzesko Forest Districts (both in Poland). Pine cone length, thickness, and weight were determined and found to be significantly different between the two locations. Pine cones were exposed to 2.45-GHz microwaves emitted by a horn antenna, which was either fixed or moving at a speed of 0.002 m s over the cones. Total microwave emission time ranged from 30 to 441 s, depending on the test variant. The measured parameters included changes in pine cone moisture content as well as the germination capacity and viability class of the extracted seeds. It was found that pine cone moisture content decreased on average by 0.3 to 6 %, depending on the amount of microwave radiation applied. It was found that pine cone size, the amount of microwave radiation, and the distance between the cones and the horn antenna affected seed germination and viability class. In most experimental variants, the seeds were damaged by microwaves. Viable seeds (classes I and II) were obtained after 30 s of exposure to microwave radiation from a fixed horn antenna positioned at a distance of 0.04 m over the cones. The application of a moving antenna positioned 0.14 m over the cones resulted in seeds of viability classes II and III following a single microwave sweep over the seeds. [ABSTRACT FROM AUTHOR]

During the last decades the Mediterranean zone in Europe has experienced an increment in the incidence of forest wildfires. This increase is partly explained by higher mean temperature and lower relative humidity, while socioeconomic change has lead to the abandonment of farms, resulting in an increase in an unusual accumulation of forest fuels, increasing the risk of wildfires. Mapping wildfire risk is highly important because wildfires are known to potentially lead to landscape changes and to modify fire regime by inducing potential changes in vegetation composition. Also, they pose a hazard to human property and life. Maps of wildfire risk based on statistical models provide a measure of uncertainty for the inferences derived from such risk maps, leaving a quantitative error margin for managers and decision takers. Further, some of the model parameters often have a physical or a biological interpretation which can give ecologists and forest engineers answers about scientific questions of interest. In this paper, we analyze the incidence of wildfires in the province of Castellón in Spain in order to identify risk factors associated with wildfire incidences during the years 2001-2006. We used the discrete nature of wildfire events to build such models using point process theory and methods and included information about elevation, slope, aspect, land use and distance to nearest road as covariates in our modeling process. Our results show that wildfire risk in Castellón is associated with all the covariates considered and that three land-use categories have the highest risk of wildfire incidence. Also, wildfire incidences are not independent and some degree of interaction exists, which indicates that the commonly used Poisson point process models are not applicable in this case, but instead area-interaction models should be considered. [ABSTRACT FROM AUTHOR]

Spatial genetic structure (SGS) in plants is primarily determined by the interaction between pollen and seed dispersal, but it is strongly affected by both evolutionary and ecological processes. SGS studies in forest species also allow evaluating the consequences of human-mediated disturbance on pollen and seed movement and designing strategies of sustainable use of native forest resources. The present paper compares fine-scale SGS between two populations of Prosopis alba: Fernandez-Forres (FF) and Campo Duran (CD), based on the variation of 12 SSR markers. Populations show different history, management, and levels of disturbance. FF is highly disturbed and fragmented by agricultural activity and stock-breeding. Although no significant differences were observed in genetic variability parameters, highly significant genetic differentiation was detected with virtually no admixture between populations. SGS was positive and significant at short distances only in the non-disturbed population of CD. Accordingly, estimated neighborhood size and effective gene dispersal are higher in FF than in CD. This result might be explained by the higher incidence of livestock in seed dispersal and the patchy structure favoring longer pollen movement and artificial thinning and selection in FF. The results are relevant to conservation and breeding programs, suggesting that the distance between seed trees to be sampled should be larger than 22 m, the estimated distance of significant SGS in P. alba. [ABSTRACT FROM AUTHOR]

F. excelsior is affected by dieback in the major part of its natural geographical range in Europe, which results in economic and ecological losses. The disease is caused by the ascomycetous fungus Hymenoscyphus fraxineus, a pathogen introduced to Europe most probably from East Asia. This paper presents data on fungi identified on F. excelsior trees representing two different stages of ash dieback in Poland. Fungal communities were identified in initial necrotic lesions on living stems and twigs using the classical method of isolation on malt extract agar and morphological and molecular analyses. In dead apical parts of stems and twigs, fungi were identified by microscopic analyses of fruit bodies formed in situ. Seventy-one fungal taxa were found in 720 samples with symptoms of initial or advanced necrosis. The most common fungus detected in initial necrotic lesions in each forest site was Hymenoscyphus fraxineus (59.2 % of analysed samples). Other frequently isolated fungi included Alternaria alternata, Diaporthe eres, Diplodia mutila, Fusarium avenaceum, F. lateritium and Phomopsis spp. Fruit bodies on dead apical parts of stems and twigs were produced mostly by Diaporthe eres, Diplodia mutila, Lophiostoma corticola, Phomopsis spp., Sirodothis sp. and Valsa cypri. Fungal communities from different sites were similar, as shown by high Sørensen similarity index values. Greatest variation in fungal community structure at the initial necrotic stage was realized by D. mutila and F. avenaceum, and at the advanced necrotic stage by D. eres, D. mutila and Phomopsis spp. Data show a close affinity of certain fungi to site, suggesting geographical relatedness. The ecological effects of distribution of the invasive H. fraxineus and of other fungi sporulating on diseased ash trees in Europe are discussed. [ABSTRACT FROM AUTHOR]

Biomass equations are a helpful tool to estimate the tree and stand biomass production and standing stock. Such estimations are of great interest for science but also of great importance for global reports on the carbon cycle and the global climate system. Even though there are various collections and generic meta-analyses available with biomass equations for mature trees, reports on biomass equations for juvenile trees (seedlings and saplings) are mainly missing. Against the background of an increasing amount of reforestation and afforestation projects and forests in young successional stages, such equations are required. In this study we have collected data from various studies on the aboveground woody biomass of 19 common tree species growing in Europe. The aim of this paper was to calculate species-specific biomass equations for the aboveground woody biomass of single trees in dependence of root-collar-diameter (RCD), height (H) and the combination of the two (RCD H). Next to calculating species-specific biomass equations for the species available in the dataset, we also calculated generic biomass equations for all broadleaved species and all conifer species. The biomass equations should be a contribution to the pool of published biomass equations, whereas the novelty is here that the equations were exclusively derived for young trees. [ABSTRACT FROM AUTHOR]

The main focus of this paper was the dynamics of Fraxinus angustifolia tree spatial patterns after the frequency of flooding events has markedly declined, especially as regards competition with Carpinus betulus and Acer campestre, the most rapidly expanding species in alluvial hardwood forests in Central Europe. The study was conducted in alluvial forests at the confluence of the Morava and Dyje rivers in the Czech Republic. A pair correlation function was used to describe the variability in tree density. Analyses were carried out for datasets from 1973, 1994 and 2006. Over the study period, F. angustifolia populations were characterised by stagnation in the number of individuals, while the number of C. betulus and A. campestre trees increased. Recruitment rates of F. angustifolia were the lowest of all species with the exception of Quercus robur. Recruits of F. angustifolia showed a strong connection to newly available space after decay of the Q. robur layer. Analysis of the elevational distribution of populations showed an increase in the stand intersection of tree species. In the absence of regular floods, F. angustifolia comes into direct competition with C. betulus and A. campestre, which are more adapted to grow in densely shaded, closed stands. [ABSTRACT FROM AUTHOR]

Net interactions between trees vary depending on environmental conditions and other factors such as stand density, age, or between-species complementarity and/or facilitation. According to the stress gradient hypothesis, positive or facilitative interactions are more frequent in high-stress environments whereas negative or competitive interactions occur in benign environments, although recent studies highlight the influence of species composition, type of stress, ontogeny, etc. on the interaction-stress gradient pattern. The aim of this paper is to analyze whether site climatic variables are a key factor in tree interactions in mixed stands of beech ( Fagus sylvatica L.) and Scots pine ( Pinus sylvestris L.). To test how site climatic conditions modify the effect of inter-specific competition on tree basal area growth and tree mortality, growth and mortality models were fitted using monospecific and mixed sample plots located in matching site conditions selected from the Spanish National Forest Inventory in the Navarra Province. Tree competition status was broken down into four terms according to size-symmetry (size-symmetric vs. size-asymmetric) and species identity (intra-specific vs. inter-specific). The results showed that the size-symmetric inter-specific component was non-significant on beech basal area growth and had a negative effect on pine growth. The effect of size-asymmetric inter-specific competition was always non-significant, resulting in a higher basal area growth when the admixed species are of a larger size. The interaction between annual precipitation and this inter-specific competition effect was much more pronounced on beech than on pine. Inter-specific competition had a negative effect on pine growth under better climatic conditions and a positive effect at dryer sites, while beech always benefited from the presence of pine, although the benefit was greater where climatic site conditions were better. In tree mortality models, pine mortality increased with the proportion of beech, while beech mortality was lower as the proportion of pine increased. Precipitation modified the inter-specific competition effect on tree mortality although the site influence was less relevant than on tree growth. For pine mortality, the negative effect of beech admixture was stronger at lower mean annual precipitation, while in the case of beech the positive effect of pine increased at higher levels of precipitation. The influence of climate on the effect of competition, the variation in their strength depending on the mode of competition (size-symmetric or size-asymmetric), along with the inter-specific competition component, highlight the importance of considering the effect of site conditions on between-species interactions when modeling tree growth and mortality. The species-specific patterns of variation in tree interactions along climatic gradients and the differences in tree growth and mortality corroborate the need to consider the nature of stress-limiting factors and species composition and the importance of analyzing both dynamic processes simultaneously. [ABSTRACT FROM AUTHOR]

A correction to this paper has been published: https://doi.org/10.1007/s10342-021-01385-w [ABSTRACT FROM AUTHOR]

Black poplar ( Populus nigra L.) is a widely distributed species that plays a crucial role in riparian forest ecosystems. Due to a reduction in its natural habitats and hybridization with introduced poplar species clones, its genetic pool is decreasing and efforts are required to preserve this species. Seeds of black poplar are short-lived and quickly lose viability during conventional storage in gene banks. Therefore, in order to preserve ex situ the genetic diversity of this species, the feasibility of seed cryopreservation in liquid nitrogen (at −196 °C, LN) for periods of 24 h and 2 years was investigated. Seeds were harvested from three individual trees (two provenances) and desiccated to different levels of water content (WC) in the range of 0.02-0.35 g g (g HO/g dry mass, g g) prior to immersion in LN. Seed germination was assessed after each treatment. P. nigra seeds tolerated desiccation to WC 0.07 g g but after severe desiccation to WC <0.05 g g exhibited a significant reduction in germination. Results indicated that all black poplar seeds, regardless of origin, year of harvesting and seed quality, could be cryopreserved for 24 h when their WC was in the range of 0.11-0.17 g g. Physiology of P. nigra seeds showed in this paper is consistent with attributes of intermediate seed storage behavior. This study provides a foundation for using cryopreservation for the ex situ conservation of P. nigra seeds. [ABSTRACT FROM AUTHOR]