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Deadwood is a prominent part of forest ecosystems. It is important for multiple forest functions, including habitat, water storage, nutrient cycling and carbon storage. Deadwood volume is now routinely measured in many large-scale inventory programs, including the national forest inventory or inventory of nationalparks or nature reserves. Policy changes, increasing climatic stress, more frequent and more intense disturbances and/or abandoning forest management will likely lead to increasing deadwood volumes in the next decades. We will explore here the available knowledge on decay of deadwood in Central Europe, focussing on carbon (C) and nitrogen (N) content and release.Decay classes can be assessed in the field and provide a potent proxy for deadwood density, pore volume and C:N ratios, based on pilot studies in Eastern Austria. Using C:N as proxy for decomposability suggest that decomposition is non-linear and that advanced decay stages have faster decomposition. Our results highlight that smaller sized deadwood (2-10 cm diameter) can store substantial amounts of C and N. Additional field work, non-destructive methods and modelling can link decay stages with time since death and allow estimating mass and volume loss by decomposing organisms.For understanding the dynamics between standing and lying deadwood we will need models that are able to predict the disintegration of trees, considering loss of less stable stem parts, like bark or sapwood. We will need continuous deadwood monitoring as well as more complex models to understand the main pathways for deadwood decay, the effects of climate on decomposition and the role of management in deadwood accumulation and dynamics. Complementing available data with new methods and models will allow us to quantify the capacity of managed and unmanaged forests for deadwood, the carbon sequestration in deadwood and its persistance in the future.References:Gschwantner T (2019) Totholz-Zunahme ausschließlich positiv? BFW Praxisinformation 20:Müller-Using S, Bartsch N (2009) Decay dynamic of coarse and fine woody debris of a beech (Fagus sylvatica L.) forest in Central Germany. European Journal of Forest Research 128, 287–296. doi:10.1007/s10342-009-0264-8.Neumann M, Hasenauer H (2021) Thinning Response and Potential Basal Area — A Case Study in a Mixed Sub‐Humid Low‐Elevation Oak‐Hornbeam Forest. Forests 12:. https://doi.org/10.3390/f12101354Neumann M, Hasenauer H (in review) A simple concept for estimating deadwood carbon in forests. Carbon ManagementOettel J, Lapin K, Kindermann G, et al (2020) Patterns and drivers of deadwood volume and composition in different forest types of the Austrian natural forest reserves. For Ecol Manage 463:118016. https://doi.org/10.1016/j.foreco.2020.118016Pietsch SA, Hasenauer H (2006) Evaluating the self-initialization procedure for large-scale ecosystem models. Glob Chang Biol 12:1658–1669. https://doi.org/10.1111/j.1365-2486.2006.01211.x

Ethiopian mixed forests have multipurpose benefits and services. However, there is a gap of information in the entire Ethiopian highlands on forest growth needed for implementation of sustainable f...

In Europe, Norway spruce forests are facing challenges due to climate change. One possible adaptive option is to enhance the resilience of forests by thinning. Usually, thinning requires two workin...

In recent decades there has been an increasing demand by ecologists for harmonized climatic data at large spatial scales and spanning long periods. Here we present easyclimate, a software package to obtain daily climatic data at high resolution (0.0083º, ~1 km) with R. The package facilitates the downloading and processing of precipitation, minimum and maximum temperatures for Europe from 1950 to 2020. Using easyclimate and given a set of coordinates (points or polygons) and dates (days or years), the user can download the climatic information as a tidy table or a raster object. In this package we implemented Cloud-Optimized GeoTIFFs which provide access to daily climate data for thousands of sites/days within minutes, without having to download huge rasters. Daily climate data are not available in many of the current climate databases and are essential for many ecological research questions and applications, including the study of the effects of extreme climatic events related to late-spring frosts, heat waves, or dry periods on plant performance. easyclimate taps the potential for climatic data and enables multiple applications in forestry, ecological and vegetation studies across Europe.

Europe has a history rich in examples of successful and less successful introductions of non-native trees (NNT) - trees with an evolutionary origin outside of Europe. NNT have been introduced for various reasons such as ornamental purposes, food production, land reclamation/amelioration and timber production. The use of NNT also causes controversies due to potential negative impacts on natural ecosystems of NNT that become invasive. Many international legal frameworks responded to the presence and use of NNT, such as international treaties and conventions ; and also the European Union deals with the issue of invasive alien species in Regulation (EU) No. 1143/2014. However, especially the national and regional responses to NNT affect current and future management decisions in the forest sector and furthermore shape forest landscapes of Europe. In this comprehensive study of the legal landscape concerning NNT we identified all relevant legislations, the different legal approaches and the regulatory intensity in every European country (except microstates). Hard and relevant soft law items at the national and sub-national (regional) level for 40 European countries were collected and proofed using a targeted questionnaire sent to country experts across Europe mainly coming from the forestry and nature conservation sector. In addition, international and national legislation information systems and databases were consulted to complete the information. Legislations included updates until June/July 2019. In total, 320 national and regional law items were identified to be relevant for the regulation of NNT in the investigated 116 legislative units (countries, and regions with own legislation) in Europe. Countries and regions were empirically categorised according to ad hoc created legislation indicators dealing with the general ban of introduction of non-native species, the generally allowed and prohibited NNT, approval mechanisms, e.g. mandatory forest management plans, and areas and cases where NNT are restricted or completely prohibited. Our study revealed a very diverse legal landscape in Europe, with a large variety of approaches being pursued to regulate NNT, and the intensity of regulation ranging from very little restrictions on the species choice and plantation surface area to a complete ban of NNT in forests.

Purpose of Review Non-native tree species (NNT) raise a range of different associations and emotions—to many citizens they are just an exotic curiosity in parks, to many conservationists they are an evil to native ecosystems that should be eradicated, to a rising group of foresters they are part of the solution to climate change and an increasing timber demand, and to others they are already daily forestry business. In this review, where we also summarise the findings of the recent COST Action FP1403 (NNEXT) ‘Non-native tree species for European forests: experiences, risks and opportunities’, we highlight opportunities and challenges in the light of climate change, ecological risks and legislative limits of growing non-native tree species in Europe. Recent Findings Few NNT in Europe show invasive behaviour and are listed as prohibited species or as species to be monitored. A larger number of NNT is utilised in productive forestry and forest restoration due to their superior growth, valuable timber properties and good performance under harsh growing conditions. Current species distribution, experiences with success and failures and environmental concerns differ profoundly across Europe, with Western Europe overall revealing higher shares in NNT and showing a stronger interest of forestry related stakeholder groups to continue planting NNT. Summary Many more NNT are already used in forestry than previously thought, but relatively few species have major importance in terms of area, mainly in western European countries. Diversification, mixing and avoidance of invasion in relation to NNT are necessities that are relatively new on the agenda. In contrast, provenance research of major NNT has been going on for many decades and now provides important information for climate change adaptation. Despite the limitations to the use of NNT either through legal restrictions or forest certification that differ considerably across Europe, the careful integration of a range of tested NNT also into future forest management planning shows a high potential for climate change adaptation and mitigation.

Purpose of Review Mechanized logging operations with ground-based equipment commonly represent European production forestry but are well-known to potentially cause soil impacts through various forms of soil disturbances, especially on wet soils with low bearing capacity. In times of changing climate, with shorter periods of frozen soils, heavy rain fall events in spring and autumn and frequent needs for salvage logging, forestry stakeholders face increasingly unfavourable conditions to conduct low-impact operations. Thus, more than ever, planning tools such as trafficability maps are required to ensure efficient forest operations at reduced environmental impact. This paper aims to describe the status quo of existence and implementation of such tools applied in forest operations across Europe. In addition, focus is given to the availability and accessibility of data relevant for such predictions. Recent Findings A commonly identified method to support the planning and execution of machine-based operations is given by the prediction of areas with low bearing capacity due to wet soil conditions. Both the topographic wetness index (TWI) and the depth-to-water algorithm (DTW) are used to identify wet areas and to produce trafficability maps, based on spatial information. Summary The required input data is commonly available among governmental institutions and in some countries already further processed to have topography-derived trafficability maps and respective enabling technologies at hand. Particularly the Nordic countries are ahead within this process and currently pave the way to further transfer static trafficability maps into dynamic ones, including additional site-specific information received from detailed forest inventories. Yet, it is hoped that a broader adoption of these information by forest managers throughout Europe will take place to enhance sustainable forest operations.

Competition for resources (light, water, nutrients, etc.) limits the size and abundance of live trees a site can support. This carrying capacity determines the potential carbon sequestration in live trees and the maximum growing stock. Lower stocking through thinning can change growth and mortality. We were interested in the relations between stand structure, increment, and mortality using a long-unmanaged oak-hornbeam forest near Vienna, Austria, as a case study. We expected lower increment for heavily thinned compared to unmanaged stands. We tested the thinning response using three permanent growth plots, in which two were thinned (50% and 70% basal area removed) and one remained unmanaged. We calculated stand structure (basal area, stem density, diameter distribution) and increment and mortality of single trees. Over ten years, the heavily thinned stand had a similar increment as that of the moderately thinned and unthinned stands. The basal area of the unthinned stand remained constant and stem density decreased due to competition-related mortality. The studied oak-hornbeam stands responded well even to late and heavy thinning, suggesting a broad “plateau” of stocking and increment for these forest types. Lower stem density for thinned stands led to a much larger tree increment of single trees, compared to the unthinned reference. The findings of this study need verification for other soil and climatic conditions.

Competition for resources (light, water, nutrients, etc.) limits the size and abundance of alive trees a site can support. This carrying capacity determines the potential carbon sequestration in alive trees as well as the maximum growing stock. Lower stocking through thinning can change growth and mortality. We were interested in the relations between stand structure, increment and mortality using a long-unmanaged oak-hornbeam forest near Vienna, Austria, as case study. We expected lower increment for heavy thinned compared to unmanaged stands. We tested the thinning response using three permanent growth plots, whereas two were thinned (50% and 70% basal area removed) and one remained unmanaged. We calculated stand structure (basal area, stem density, diameter distribution) and increment and mortality of single trees. The heavy thinned stand had over ten years similar increment as the moderate thinned and unthinned stands. Basal area of the unthinned stand remained constant and stem density decreased due to competition-related mortality. The studied oak-hornbeam stands responded well even to late and heavy thinning suggesting a broad “plateau” of stocking and increment for these forest types. Lower stem density for thinned stands lead to much larger tree increment of single trees, compared to the unthinned reference. The findings of this study need verification for other soil and climatic conditions.

In view of the increasing demand for forest resources in Europe, it is an option to foster the use of non-native tree species that can keep pace with the rapidly changing environmental conditions, such as Douglas-fir (Pseudotsuga menziesii). Thus, sufficient knowledge of how to manage such introduced species is highly required. In this study, we investigate theoretical silvicultural management options of Douglas-fir for forests in central Europe. We follow a three-step approach: (i) we collect the current central European management practices based on 434 Douglas-fir stands managed by 19 forest companies in Eastern Austria and Southern Germany using a survey. (ii) We calibrate and validate a Douglas-fir parameter set for the tree growth simulator MOSES so that we are able to (iii) simulate the silvicultural management options of Douglas-fir management. Our simulation results suggest: in mixed stands, Douglas-fir should be planted in mono-species patches. This leads to about six times higher productivity compared to a random arrangement. Natural regeneration is possible but requires active management at further development since the productivity might decrease up to 86% when growing in association with the highly competitive native tree species, Common beech (Fagus sylvatica). Intensive tending, as well as thinning, yields a surplus stem volume production of more than 30% in comparison with a moderate intervention. Even if our simulation results were not validated in the field, this analysis suggests that modeling as a heuristic tool is a useful instrument for forest managers in the decision-making process.

The management of non-native tree species in European forests has a long history, but the information on the current number and geographic distribution of these species in European forests is incom...

Ailanthus altissima is a common tree species of the European non-native flora. In Eastern Austria, Ailanthus has both a long tradition, dating back to the late 18th century, and a high frequency of occurrence. Here, we apply molecular markers from the nuclear and chloroplast DNA in order to study the origin, as well as the clonal and genetic structure of the species in forest stands of this region. Our results indicate a single area of origin for all our study populations from the north-eastern part of the native range, in agreement with historical reports. Within populations, vegetative reproduction has resulted in extensive clonal structures at some sites. Long presence and repeated vegetative recruitment might have led to expansion of clones in areas of early introduction. In addition, limited mate availability may also have promoted vegetative reproduction. Tests for recent bottlenecks were significant in almost all stands, possibly reflecting founder effects since the introduction of Ailanthus in our study area. Among populations, we found a very pronounced and significant genetic structure, which did not follow a spatial pattern. We argue that founder effects due to population establishment with a low number of propagules – whether naturally or artificially – have caused genetic drift and a structured gene pool. The lack of spatial pattern or isolation-by-distance suggests that seed transfer by humans might have been a major factor shaping the genetic variation of Ailanthus in Eastern Austria.

The structure of a forest dictates its function, vulnerability to mortality, and ecosystem services it provides. Many aspects of the environment and management determine forest structures, such as canopy height, stand density, carbon content, etc. Environmental factors, such as climate, limit the extent to which management can maximize structures of a forest. By understanding how climate limits forest structures over large landscapes we can better quantify the potential upper limit that a forest structure can achieve independent of management. Further, by quantifying how climate limits forest structures we can deepen our understanding of the impact climate change has had and will have on our forest resources and services. This type of information goes beyond quantifying how climate will impact the pools and fluxes of a forest, which is typically done for climate change studies over large landscapes. Estimating how climate change will impact structures will allow us to quantify how climate change will impact resources and services unquantifiable by pools and fluxes alone – such as biodiversity, habitat suitability, and market values. We quantified how maximum and minimum temperatures, and precipitation limit 3 forest structures, diameter at breast height, height, and basal area across the European continent. We found that climate zones exist that maximize each forest structure. Further, we estimated how climate change since the 1950’s has influenced the potential structures of European forests by assessing eight individual forests throughout Europe and then Europe as a whole. All three forest structures are limited in different ways depending on their location in Europe. Though some individual forests have seen a benefit from climate change, European forests on average have lost 5.0%, 1.7% and 6.5% of potential forest diameter, height and basal area respectively. Further, the extremes of the climate values in our study, which may support endemic life, have already begun to vanish from the entire continent.

Litterfall is a major, yet poorly studied, process within forest ecosystems globally. It is important for carbon dynamics, edaphic communities, and maintaining site fertility. Reliable information on the carbon and nutrient input from litterfall, provided by litter traps, is relevant to a wide audience including policymakers and soil scientists. We used litterfall observations of 320 plots from the pan-European forest monitoring network of the “International Co-operative Programme on Assessment and Monitoring of AirPollution Effects on Forests” to quantify litterfallfluxes. Eight litterfall models were evaluated (four using climate information and four using biomass abundance). We scaled up our results to the total European forestarea and quantified the contribution of litterfall to the forest carbon cycle using net primary production aggregated by bioregions (north, central, and south) and by forest types (conifers and broadleaves). The 1,604 analyzed annual litterfall observations indicated an average carbon input of 224 g C · m2· year 1 (annual nutrient inputs 4.49 g N, 0.32 g P, and 1.05 g K · m2), representing a substantial percentage of net primary production from 36% in north Europe to 32% in central Europe. The annual turnover of carbon and nutrient in broadleaf canopies was larger than for conifers. The evaluated models provide large-scale litterfall predictions with a bias less than 10%. Each year litterfall in European forests transfers 351 Tg C, 8.2 Tg N,0.6 Tg P, and 1.9 Tg K to the forestfloor. The performance of litterfall models may be improved by including foliage biomass and proxies for forest management.

National and international carbon reporting systems require information on forest carbon stocks. This information can be derived from national forest inventory data and remote sensing. Here we present the conceptual challenges in assessing forest resources across Europe by combining MODIS satellite versus terrestrial driven NPP estimates calculated from 13 national forest inventory (NFI) data covering 200.000 sampling plots. The results suggest that MODIS NPP predictions using local daily climate data and addressing stand desnsity effects, provide realistic forest productivity estimates. Ignoring these effects leads to an overestimation in the estimated carbon storage of European forests derived from satellite data.

Due to its productivity and potential to adapt to the expected climate change, the Douglas-fir is one of the most important commercial non-native forest tree species in Europe. Currently, seeds from both non-native European and native American seed stands are used for plantations. In this study, we investigate European seed lots for their native origin (variety and potential geographic origin in America) and assess the adaptability, growth and survival potential of European versus American Douglas-fir seed lots. We compare the genetic diversity, morphological characteristics such as height (h), root collar diameter (rcd) and the ratio of h/rcd, and the timing of bud burst. We investigate 852 1-year-old seedlings from 10 different US and European seed lots representing 5 provenance regions which are sold in Germany and Austria. Seedlings are genotyped for 13 nuclear SSRs and analysed together with reference data set and standard genetic structuring and assignment methods. Adaptive traits of morphological characteristics and timing of bud burst of the seedlings are recorded and statistically analysed. The results show that the investigated European seedlings originate from recommended American native seed sources and represent both varieties and inter-varietal admixed individuals. European seedlings have a lower genetic diversity versus the American seedlings and native populations. They show significant differences in the adaptive traits such as morphological characteristics and timing of bud burst. According to the genetic diversity indices, certified North American Douglas-fir seed sources should be preferred for planting in Central Europe.

Tree mortality is an important process in forest ecosystems, frequently hypothesized to be highly climate sensitive. Yet, tree death remains one of the least understood processes of forest dynamics. Recently, changes in tree mortality have been observed in forests around the globe, which could profoundly affect ecosystem functioning and services provisioning to society. We describe continental-scale patterns of recent tree mortality from the only consistent pan-European forest monitoring network, identifying recent mortality hotspots in southern and northern Europe. Analyzing 925,462 annual observations of 235,895 trees between 2000 and 2012, we determine the influence of climate variability and tree age on interannual variation in tree mortality using Cox proportional hazard models. Warm summers as well as high seasonal variability in precipitation increased the likelihood of tree death. However, our data also suggest that reduced cold-induced mortality could compensate increased mortality related to peak temperatures in a warming climate. Besides climate variability, age was an important driver of tree mortality, with individual mortality probability decreasing with age over the first century of a trees life. A considerable portion of the observed variation in tree mortality could be explained by satellite-derived net primary productivity, suggesting that widely available remote sensing products can be used as an early warning indicator of widespread tree mortality. Our findings advance the understanding of patterns of large-scale tree mortality by demonstrating the influence of seasonal and diurnal climate variation, and highlight the potential of state-of-the-art remote sensing to anticipate an increased likelihood of tree mortality in space and time.

Pan-European gridded datasets derived from a single methodology to inform researchers, policy makers and conservationists on the state of forest structures would improve our ability to study forests independent of political boundaries and along various gradients. Although National Forest Inventory (NFI) data provide information on the characteristics of forests, including carbon content, volume, height, and age, such spatial data is not available across Europe. Before this study, remotely sensed data covering all of Europe had not been utilized to produce multiple European-focused forest structure datasets over the entire continent that are methodologically consistent and comparable. We used existing European data to develop a pan-European dataset covering tons of live tree carbon and volume per hectare, mean tree height and mean tree age by integrating remotely sensed and harmonized NFI data from 13 different European countries. We produced a pan-European map for each of the four key variables on a 0.133° grid representing the time period 2000–2010.

Moses (MOdelling Stand rESponse) is a distance and potential-dependent single-tree growth simulator. It consists of a diameter and height increment model, a dynamic crown model and models that calculate mortality and regeneration. It was originally calibrated for spruce, beech and pine forests in Austria and has been recalibrated several times throughout the years. In this study, we recalibrated and validated the increment models and the mortality model within MOSES using the latest large and holistic dataset based on monitoring and permanent inventory plots for seven of the most common tree species in Europe (five for the mortality model). These plots were mainly from Austria and Switzerland, as well as Germany. In addition, we calibrated sets of coefficients for the “species groups” (i) other broadleaf and (ii) other conifer trees. The total dataset comprises 278,979 repeated tree measurements, 56,312 of them were used for calibration and 222,667 for validation. The validation of the newly parameterized growth and mortality models exhibit consistent and unbiased estimates for tree growth in central European forests using the MOSES simulator.

© 2019 The Authors FORMIT-M is a widely applicable, open-access, simple and flexible, climate-sensitive forest management simulator requiring only standard forest inventory data as input. It combines a process-based carbon balance approach with a strong inventory-based empirical component. The model has been linked to the global forest sector model EFI-GTM to secure consistency between timber cutting and demand, although prescribed harvest scenarios can also be used. Here we introduce the structure of the model and demonstrate its use with example simulations until the end of the 21st century in Europe, comparing different management scenarios in different regions under climate change. The model was consistent with country-level statistics of growing stock volumes (R 2 = 0.938) and its projections of climate impact on growth agreed with other studies. The management changes had a greater impact on growing stocks, harvest potential and carbon balance than projected climate change, at least in the absence of increased disturbance rates. ispartof: Environmental Modelling and Software vol:115 pages:128-143 status: published

Many spatial vegetative physiological and environmental impact studies demand consistent as well as fine resolution daily meteorological data, which is often unavailable. This problem is evident when studies and applications focus at the regional and local scale. Meteorological stations cannot provide the needed data due to their irregular locations and several associated shortcomings such as missing data. Climate data from global sources like the National Centers for Environmental Prediction (NCEP) and WorldClim are provided at a coarse resolution which makes them inappropriate to use directly at regional and local scales. In order to circumvent this problem, we downscaled daily WorldClim and NCEP global climate grids to produce weather data sets using a delta method to 0.0083‾ (approximately 1 × 1 km) spatial resolution for the Amhara region of northwestern Ethiopia. The downscaled data set includes daily precipitation, and minimum and maximum temperature from 1979 to 2010. The drizzle effect in the downscaled data set was first eliminated by using a rain threshold that removed values of

Forests provide critical ecosystem services that ensure the sustainability of the environment and society. To manage forests on large scales, spatially explicit gridded data that describes the characteristics of these forests over the entire study area are required. There have been multiple efforts to create such data on regional and global scales. This type of gridded spatially explicit data on forest characteristics are typically done by integrating terrestrial forest inventory (NFI) and satellite-based remotely sensed data. Many studies that incorporate remotely sensed data and forest inventory data often directly compare pixels to inventory plots. The standard resolution of 0.0083° is typically used to integrate these two types of data sets. There is an assumption that, when producing gridded data sets incorporating forest inventory data, the finer the resolution the better the information. This assumption may seem intuitive, however at this resolution, in Europe, each 0.0083° cell has on average 1 NFI plot, which results in a sample with 0 degrees of freedom that represents 0.02% of the cell area. In this study, we challenge this assumption and we quantify the optimal resolution with which to compare and combine remotely sensed and NFI data from the largest collated and harmonized NFI data set in Europe including 196,434 plots. We determined that aggregating data with an original resolution of 0.0083° to between 0.0664° and 0.266° (or × 8 to × 32) produces the best agreement between these two forest inventory and remotely sensed data sets, and the lowest standard error in NFI data, and maintains the majority of the local-level spatial heterogeneity.

We assessed the impact of anthropogenic activities such as selective felling and resource extraction on plant diversity and forest structure in the broad-leaved forests of Bhutan. The forest area was grouped into three zones according to human influence: settlement-agriculture, semi-disturbed, and natural forest. A total of 140 plant species were identified. Maximum species richness of trees (8 species/plot) was recorded in natural forests and least in the settlement-agriculture zone (3 species/plot). Shannon (1.73 ± 0.62) and Simpson diversity (5.49 ± 2.97) indices were highest for the natural forest zone as compared to the semi-disturbed (0.92 ± 0.74, 2.70 ± 2.05) and settlement-agriculture zones (0.74 ± 0.74, 2.24 ± 2.13). The density and basal area of trees decreased from 373 N ha−1 and 37.9 m2 ha−1 in the natural forest zone to 114 N ha−1 and 5.7 m2 ha−1 in the settlement-agriculture zone. The diameter distribution revealed a lack of commercial tree species in the higher dbh classes from the ...

Little is known about sustainable forest management and tree growth in the Amazon forest. Reliable growth data from trees are very important in the context of forest management. Tree-characteristics such as architecture and competition are associated with diameter growth. Previous studies analyzing tree growth have indicated that these variables can describe these effects for temperate and boreal forests. However, the role of these effects for the growth of tropical trees needs to be enhanced for forest management practices. Here, we reconstructed the periodic annual basal area increment ( BAI i cm 2 yr −1 ) of four long-lived timber species from the Amazon forest of Brazil: (i) Cedrela odorata, (ii) Amburana cearensis, (iii) Copaifera pauper and (iv) Swietenia macrophylla to investigate the growth development. The study focuses on (i) drivers important for individual tree growth, (ii) calibration of an individual tree basal area increment model for each of the four species, and (iii) assessing the practical implementation of our findings for enhancing sustainable forest management of these four tree species in the Amazon rainforest. The results exhibit a significant relationship between increasing basal area increment versus increasing crown length and decreasing competition expressed by Hegyi’s index. Trees sampled in densities greater than 25 m 2 ha −1 had their BAI % significantly reduced. For Cedrela an additional negative impact on basal area increment from liana load is evident. Our findings reinforce the importance of release trees to obtain better crown exposure.

Key message Douglas-fir growth correlates with the climate, the soil moisture regime, and the soil nutrient status, reflecting a broad physiological amplitude. Even though planting this non-native tree species is suggested as a viable strategy to improve adaptiveness of European forests to a more extreme climate and to assure future productivity, the expected temperature increase may induce a decline in forest stand productivity for Douglas-fir in already warm and dry regions. Context Tree species selection is one of the most important forest management decisions to enhance forest productivity and stand stability on a given site. Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii), a non-native species from north-western America, is seen as an important additional species option for adapting Central European forests to a changing climate. Aims This study assesses Douglas-fir forest productivity derived from site conditions. We investigate climatic and physico-chemical soil characteristics and productivity of 28 mature Douglas-fir stands growing on siliceous, as well as carbonate bedrock material in southern Germany and north-eastern Austria. Methods The importance of climatic and physico-chemical soil characteristics was analyzed with the machine learning method Random Forests. Results The results show that Douglas-fir growth correlates with climate, soil moisture, and soil nutrient availability derived from ten climatic and physico-chemical soil parameters. Conclusion The broad pH optimum between 4.5 and 7.2 reflects the broad physiological amplitude of Douglas-fir, and no significant differences were detectable between carbonate and siliceous bedrock. We also conclude that climate change may induce a forest stand productivity decline, because lower productivity with the highest mean summer temperature across our study range was observed at the warmest sites in Eastern Austria. Electronic supplementary material The online version of this article (10.1007/s13595-019-0805-3) contains supplementary material, which is available to authorized users.

Forests are a key player within the global carbon cycle and reforestation is an important climate change mitigation mechanism. In this study, we identify potentially suitable areas for reforestation to assess the carbon sequestration potential in the highly deforested and degraded Amhara region of Ethiopia. We apply biogeochemical mechanistic ecosystem modelling to predict the amount of carbon that can be potentially sequestered within different time horizons. Since human intervention plays a key role within the Amhara region, three different forest management scenarios and five different rotation periods following reforestation are tested: (i) unthinned, (ii) removal of 5% of the stem carbon every 20 years (thinning 1), and (iii) removal of 10% stem carbon every 20 years (thinning 2), as well as a rotation period of 10, 30, 50, 100, and 150 years. Sustainable management of reforested land is addressed by implementing the so called ‘Normal-forest’ system (equal representation of every age class). This ensures the long term sequestration effect of reforested areas. The study shows that 3.4 Mha (Mha = Million hectare) of land, including bare land (0.7 Mha), grass land (1.2 Mha), and shrub land (1.5 Mha) can be considered as ecologically potentially suitable for reforestation. Assuming a 100 year rotation period in a ‘Normal-forest’ system, this shows that a total net carbon sequestration potential of 177 Tg C (10.8 Tg C in the soil and 165.9 Tg C aboveground, Teragram = 1012 g) is possible, if all 3.4 Mha are replanted. The highest total net carbon sequestration (soil and aboveground) was evident for the Highland-wet agro-ecological zone, whereas the lowest values are typically in the Midland-dry zone. The highest net aboveground carbon sequestration was predicted for reforestations on current grass land and shrub land versus bare land, whereas the highest net soil carbon sequestration was predicted on current bare land, followed by grass land and shrub land.

Since the nineteenth century, Douglas-fir seed sources have been widely used for establishment of forest stands outside its natural distribution range. In Europe, some of these old Douglas-fir stands are registered as seed stands and provide seed sources for nurseries, although it is unclear from which region in North America they originate. In recent years, the interest in planting Douglas-fir has increased substantially because the species is seen as a potential adaptation option to climate change. This makes the assignment of European Douglas-fir stands of unknown seed origin to their geographic origin in North America increasingly important, because the genetic quality of these plantations must be guaranteed. In this study, we use 13 nuSSR loci to investigate the origin of 67 Austrian and German Douglas-fir stands of unknown origin. We performed a hierarchical Bayesian cluster analysis using 38 native Douglas-fir populations. The resulting clusters are used as reference populations to assign the 67 Central European Douglas-fir stands from Austria and Germany planted more than 80 years ago. Our results suggest that the majority of our investigated Douglas-fir stands come from central Washington (USA), the recommended seed zones for Central Europe. Some stands were located outside the suggested area, e.g. central Oregon and Santa Fe (New Mexico). The accuracy assessment of our approach revealed the best performance for the highest hierarchical level, e.g. assigning populations either to the coastal or the Rocky Mountain variety. As expected, the uncertainty increases with decreasing hierarchical level. The final assessment, if an admixture of seed sources within the European Douglas-fir stands is evident suggests that 23 of the Douglas-fir stands show an admixture which was not detected in our Douglas-fir reference populations growing in the natural distribution range.