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Mixed-species forests can provide higher levels of ecosystem functions and services and can be more resistant and resilient in the face of global change. While many studies focus on the growth and yield of mixed forests, fewer have examined the underlying processes. Inter- or intra-specific differences and interactions influence tree- and stand-level light absorption by determining the vertical structure of stratified canopies, stand density, leaf area index, and the size or allometry of trees. While canopy light absorption is a very important process, it is difficult to quantify it for individual species within a mixture and is rarely examined. A detailed tree-level model (MAESTRA) was used in combination with measurements of tree sizes and stand structures to examine effects of mixing on absorbed photosynthetically active radiation (APAR) in 41–63-year-old stands of Pseudotsuga menziesii and Fagus sylvatica at three sites in Bavaria, Germany. The effects of initial stand density on APAR were analysed in 46-year-old P. menziesii stands of a spacing experiment at two sites. At the tree level, mixing increased mean height and leaf area, growth (185% higher) and APAR (85% higher) of P. menziesii at all sites. Mean tree heights and crown sizes of F. sylvatica were larger in mixtures, while recent growth rates and APAR were not significantly different to monocultures. Planting density did not influence mean tree variables (e.g. height, leaf area, crown volume), because any initial spacing effects had been gradually removed by thinning across all treatments. At the stand level, there were no differences in growth, basal area or in the annual growth per annual APAR (light use efficiency, LUE) between monocultures and mixtures. The highest APAR values were observed in P. menziesii monocultures, while the lowest APAR values were observed in F. sylvatica monocultures. While mixing these species may not increase stand-level growth during later phases of development, mixing accelerated initial growth of individual trees and reduced the time to reach target diameters, which are both important aspects in adapting forests to global change. [ABSTRACT FROM AUTHOR]

In recent years, direct seeding as a means of stand establishment has experienced a revival. Among other things it allows for an undisturbed root development and is assumed to be cost-efficient. While success factors have been worked out through numerous experiments, sound overviews of success and failure in practice are scarce. With the goals of (i) quantifying the success proportion and (ii) extracting the associated influencing factors, we conducted an inventory of direct seedings of Douglas fir in Northern Germany and fitted a hurdle negative binomial regression model to the data. The results reveal a high variability of plant density within, as well as between stands. We could attribute these differences, and thus the success, to stocking degree of the shelter, seed amount and age. The model shows both, a high precision and accuracy, and respects previous physical and biological knowledge of the data-generating mechanisms. [ABSTRACT FROM AUTHOR]

Adult individuals and seeds of two mixed stands of coastal and interior Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) were analysed for genetic differentiation between the two varieties and evidence of intervarietal pollination. Clear genetic discrimination between the two varieties was observed based on multilocus evaluation of nine microsatellite markers using other Douglas-fir stands of known variety composition for comparison. Analysis of pollination distances showed that 80% of pollinations took place within a distance of about 44–55 m. Analysis of stand structure showed clearly separated areas of mainly coastal or interior Douglas-fir within both stands. Together with short pollination distances this led to an apparent dominance of intravarietal pollinations. However, analysis of pollination partners of trees growing near the border of the variety specific areas, does not indicate the existence of reproductive barriers between trees of the two varieties growing in mixed stands. Therefore, commercial seed harvesting in mixed stands should be avoided if the production of seed lots of pure coastal or interior Douglas-fir is intended. [ABSTRACT FROM AUTHOR]

Winter storms cause severe damage in German forests. Different modelling approaches have already been used to try and map endangered areas to minimize the risk of wind damage by stand adaption. Prevalent models for Germany include empirical-statistical and hybrid-mechanistic models, such as ForestGALES (FG). As of yet, FG is not extensively used in Germany as its parametrization requires extensive experimental efforts to derive regionally sensitive species-specific parameters. Here, we implement a statistical calibration approach for German forest conditions with observed damage from single tree data, soil types, topography (topex) and gust speed data. We use simulated annealing to generate new species-specific values for the tree species, Norway spruce, European beech, and Douglas fir from within the range of all coniferous (deciduous) species for Norway spruce and Douglas fir (European beech) and an additional 10 % buffer around the default species-specific values for each species. We compare two optimization approaches: First, we aim to maximize the Matthew's correlation coefficient (MCC), which is calculated from the confusion matrix, applying a fixed classification threshold of 0.5. In comparison to the optimization at a fixed threshold, we optimized the species-specific parameters by maximizing the area-under-curve (AUC) value directly generated from the receiver-operator characteristic (ROC) analysis. We compare our statistical parametrizations for the considered species to those currently implemented in FG and validate the resulting damage probabilities based on confusion matrices and related performance measures. We created separate parametrizations for a single-tree and stand-wide analysis of storm damage risk, which we validated with gust speed data for Germany. Our results show, that for the single-tree method, MCC improved for all species: By 0.26 (0.22) for the calibration (validation) subset for Douglas fir, by 0.22 (0.18) for Norway spruce and by 0.08 (0.05) for European beech. The optimization for the stand-method shows an increase in MCC as well, with results not being considered due to low numbers of observation data. We show that for German forests, FG's predictive capability can be improved by statistical optimization when no tree-pulling data is available, which could be valuable for creating further regionalizations of FG. • Modelling storm damage risk for German forests using ForestGALES. • Regional parametrization using statistical optimization. • Adjusted model has higher predictive capacity in storm damage risk estimations. [ABSTRACT FROM AUTHOR]

Recent biodiversity loss has emphasized the necessity to critically evaluate the consequences of human alterations of forest ecosystems. Stand diversification via tree species mixtures and the use of non‐native trees are two such alterations currently gaining importance as climate change adaptations. However, the effects of local versus regional tree mixing on associated biodiversity and notably the modifying role of tree species growing outside their natural range remain poorly understood.We assessed how monocultures and mixtures of native and introduced tree species influence the taxonomic and functional diversity of bird communities at stand and landscape scales in north‐west Germany. We focused on the dominant natural tree species (Fagus sylvatica) and economically important conifer species planted outside their natural range (the native Picea abies and non‐native Pseudotsuga menziesii).We found that bird species richness and functional diversity were generally higher in pure and mixed stands of native F. sylvatica than in pure conifer stands, especially in comparison to non‐native P. menziesii. These differences were particularly strong at the landscape scale. Pure conifer stands harboured only a reduced set of functionally similar bird species. Structural diversity based on tree microhabitat availability emerged as a key predictor of bird diversity.Synthesis and applications. Our study suggests that tree species mixtures do not necessarily increase bird diversity compared to pure stands of native trees, but can promote bird diversity relative to pure stands of species planted outside their natural range. Moreover, local mixtures, rather than a mosaic of pure stands, may promote bird diversity also at the landscape scale. By contrast, pure stands of tree species planted outside their natural range can increase biotic homogenization of forest birds. Promoting structural diversity of microhabitats via tree retention and ensuring that non‐native trees are planted in mixtures with native trees may alleviate potential limitations of climate change‐oriented management for biodiversity. [ABSTRACT FROM AUTHOR]

The non-native Douglas fir (Pseudotsuga menziesii) is widely distributed in Europe and promoted by forestry due to its assumed resistance against climate change. An increasing cultivation area is, however, viewed critically by nature conservation as negative effects on native biodiversity and naturalness are expected. We investigated plant species diversity and composition in two strict forest reserves (SFR) dominated by Douglas fir in southwest Germany. These reserves were established in the years 2001/2002 to study the development of Douglas fir forests after management abandonment. Vegetation surveys were conducted in 2005 and repeated in 2017. We used re-survey data from a nearby SFR dominated by native tree species as a reference. The understory vegetation showed consistent development after management abandonment, irrespective of tree species identity and origin. It became less diverse and more shade-tolerant over time due to missing soil disturbance and decreasing light availability. In contrast to a native canopy, though, Douglas fir promoted the share of generalist species. Regeneration of Douglas fir largely decreased in the SFRs underlining its competitive weakness against native tree species, mainly against European beech (Fagus sylvatica). Thereby, regeneration patterns of Douglas fir in the SFR were similar to those observed in the native range. [ABSTRACT FROM AUTHOR]

Most of Central Europe's economically important tree species have suffered vitality losses, growth decline and locally increased mortality during recent hot droughts. Foresters thus require comparative assessments of the major timber species' climate vulnerability. This dendroecological study compares long-term radial growth trends (basal area increment; BAI) and climate-growth relationships of (co-)dominant trees of the major timbers European beech (Fagus sylvatica L.) , sessile oak (Quercus petraea (Matt.) Liebl.), Scots pine (Pinus sylvestris L.) and Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) along a precipitation gradient (834 − 570 mm yr−1) in the lowlands of Northern Germany on deep sandy to sandy-loamy soils with the aim to explore the species' climate vulnerability and to assess the adaptive potential to reduced precipitation. The BAI of Douglas fir and beech has decreased in recent decades at most sites, while pine and oak growth was predominantly stable or has increased. Yet, the growth synchrony of all species has recently increased at some (or all) stands, hinting at the impact of increasing climatic stress. Increasing BAI at drier sites may indicate successful acclimation to reduced precipitation in oak and pine. The conifers profited primarily from sufficient moisture in late-summer and a warmer February and March, the broadleaf trees from a moister and cooler previous summer. Winter temperature emerged as a new driver of growth in pine, Douglas fir and oak, which may promote pine and oak growth at some sites through reduced winter cold stress. We conclude that all four species, but especially Douglas fir and beech, are vulnerable to climate warming in the Northern German lowlands. • Stem growth declined in all species, especially in Douglas fir and European beech. • Growth decline was accompanied by rising growth synchrony and crown vitality loss. • Water availability in summer and warm winters are main drivers of growth. • Acclimation to increasing aridity was often insufficient, especially at moist sites. • We recommend planting alternative timber species together with sessile oak. [ABSTRACT FROM AUTHOR]

Tree ring analyses can assist in revealing the effect of gradual change in climatic variables on tree growth. Dendroclimatic analyses are of particular importance in evaluating the climate variables that affect growth significantly and in determining the relative strength of different climatic factors. In this study, we investigated the growth performance of Pinus sylvestris, Picea abies, and Pseudotsuga menziesii in northern Germany using standard dendrochronological methods. The study further analyzed tree growth responses to different climatic variables over a period of a hundred years. Both response function analysis and moving correlation analysis confirmed that the climate and growth relationship is species-specific and variable and inconsistent over time. Scots pine and Douglas fir growth were stimulated mainly by the increase in winter temperatures, particularly the January, February, and March temperatures of the current year. In contrast, Norway spruce growth was stimulated mainly by the increase in precipitation in May, June, and July and the increase in temperature in March of the current year. Climate projections for central Europe foresee an increase in temperature and a decrease in the amount of summer precipitation. In a future, warmer climate with drier summers, the growth of Norway spruce might be negatively affected. [ABSTRACT FROM AUTHOR]

Mixed-species forests are, for multiple reasons, promising options for forest management in Central Europe. However, the extent to which interspecific competition affects tree hydrological processes is not clear. High-resolution dendrometers capture subdaily variations in stem diameter; they can simultaneously monitor stem growth (irreversible changes in diameter) and water status (reversible changes) of individual trees. Using the information on water status, we aimed to assess potential effects of tree species mixture, expressed as local neighborhood identity, on night-time rehydration and water stress. We deployed 112 sensors in pure and mixed forest stands of European beech, Norway spruce and Douglas fir on four sites in the northwestern Germany, measuring stem diameter in 10-min intervals for a period of four years (2019-2022). In a mixture distribution model, we used environmental variables, namely soil matric potential, atmospheric vapor pressure deficit, temperature, precipitation and neighborhood identity to explain night-time rehydration, measured as the daily minimum tree water deficit (TWDmin). TWDmin was used as a daily indicator of water stress and the daily occurrence of sufficient water supply, allowing for stem growth (potential growth). We found that species and neighborhood identity affected night-time rehydration, but the impacts varied depending on soil water availability. While there was no effect at high water availability, increasing drought revealed species-specific patterns. Beech improved night-time rehydration in mixture with Douglas fir, but not in mixture with spruce. Douglas fir, however, only improved rehydration at a smaller share of beech in the neighborhood, while beech dominance tended to reverse this effect. Spruce was adversely affected when mixed with beech. At species level and under dry conditions, we found that night-time rehydration was reduced in all species, but beech had a greater capacity to rehydrate under high to moderate soil water availability than the conifers, even under high atmospheric water demand. Our study gives new insights into neighborhood effects on tree water status and highlights the importance of species-specific characteristics for tree-water relations in mixed-species forests. It shows that drought stress of European beech can be reduced by admixing Douglas fir, which may point towards a strategy to adapt beech stands to climate change., (© The Author(s) 2024. Published by Oxford University Press.)

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]

In Europe, some non-native tree species (NNT) are classified as invasive because they have spread into semi-natural habitats. Yet, available risk assessment protocols are often based on a few limited case studies with unknown representativeness and uncertain data quality. This is particularly problematic when negative impacts of NNT are confined to particular ecosystems or processes, whilst providing valuable ecosystem services elsewhere. Here, we filled this knowledge gap and assessed invasion risks of two controversially discussed NNT in Germany (Quercus rubra L., Pseudotsuga menziesii (Mirb.) Franco) for broad forest types using large scale inventory data. For this purpose, establishment success of natural regeneration was quantified in terms of cover and height classes. The current extent of spread into protected forest habitats was investigated in south-west Germany using regional data. Establishment was most successful at sites where the NNT are abundant in the canopy and where sufficient light is available in the understory. Natural regeneration of both NNT was observed in 0.3% of the total area of protected habitats. In forest habitats with sufficient light in the understory and competitively inferior tree species, there is a risk that Douglas fir and red oak cause changes in species composition in the absence of management interventions. The installation of buffer zones and regular removal of unwanted regeneration could minimize such risks for protected areas. Our study showed that forest inventories can provide valuable data for comparing the establishment risk of NNT amongst ecosystem types, regions or jurisdictions. This information can be improved by recording the abundance and developmental stage of widespread NNT, particularly in semi-natural ecosystems. [ABSTRACT FROM AUTHOR]

Planting non-native tree species, like Douglas fir in temperate European forest systems, is encouraged to mitigate effects of climate change. However, Douglas fir monocultures often revealed negative effects on forest biota, while effects of mixtures with native tree species on forest ecosystems are less well understood. We investigated effects of three tree species (Douglas fir, Norway spruce, native European beech), on ground beetles in temperate forests of Germany. Beetles were sampled in monocultures of each tree species and broadleaf-conifer mixtures with pitfall traps, and environmental variables were assessed around each trap. We used linear mixed models in a two-step procedure to disentangle effects of environment and tree species identity on ground beetle abundance, species richness, functional diversity and species assemblage structure. Contradictory to our expectations, ground beetle abundance and functional diversity was highest in pure Douglas fir stands, while tree mixtures showed intermediate values between pure coniferous and pure beech stands. The main drivers of these patterns were only partially dependent on tree species identity, which highlights the importance of structural features in forest stands. However, our study revealed distinct shifts in assemblage structure between pure beech and pure Douglas fir stands, which were only partially eased through mixture planting. Our findings suggest that effects of planting non-native trees on associated biodiversity can be actively modified by promoting beneficial forest structures. Nevertheless, integrating non-native tree species, even in mixtures with native trees, will invariably alter assemblage structures of associated biota, which can compromise conservation efforts targeted at typical species composition. [ABSTRACT FROM AUTHOR]

Non-native tree species (NNT) that pose risks to biodiversity are classified as 'invasive' in some European countries. However, country-specific risk assessment methods may lead to different results for the same NNT between countries of comparable growth conditions, raising doubts about the reliability of risk classifications. Here, we analysed six risk assessment tools used in Germany and adjacent countries for their practical applicability and consistency using four NNT (Fraxinus pennsylvanica Marsh. Paulownia tomentosa (Thunb. ex Murray), Pseudotsuga menziesii (Mirb.) Franco and Quercus rubra L.) as case studies. Using these tools to classify risks for the same NNT and reference area (Germany) yielded inconsistent results for all NNT. The reasons for this were (1) differences in classification and weighting of criteria, (2) a lack of data to quantify invasion risks and (3) uncertainties related to assessment methodologies. Moreover, the tools fail to distinguish between risks posed by NNT in different sites. We suggest that instead the risks should be assessed for different ecosystem types by using site-specific inventory data covering the establishment, spread and potential impact of NNT. Our recommendations provide a foundation for developing a consistent, systematic Pan-European approach to assess invasiveness while addressing both risk and forest management aspects. [ABSTRACT FROM AUTHOR]

Highlights • Evaluation of different sized approved Douglas-fir seed stands in Germany. • Improvement of the quality of forest reproductive material. • Selfing rate increased in correlation with inbreeding effects. • The loss of alleles at descending size cannot be compensated by pollen from outside. • The basic requirements should be adapted for approved seed stands in Germany. Abstract Douglas-fir (Pseudotsuga menziesii), native to western North America, was introduced to Europe about 150 years ago. Nowadays it represents the most frequent non-native forest tree species in Germany, covering about 2% of the forest area. While seeds were initially imported from its natural distribution range, the German seed market is now mainly supplied with seeds from local stands. In this study we examined four representative, different sized artificial Douglas-fir stands. We used microsatellite markers to characterise adults and offspring by analysing the genetic diversity and mating system. We detected a negative correlation of population size and genetic diversity. The loss of alleles with descending population sizes cannot be compensated by pollen from outside of the stand. The results showed an increased selfing rate (1–13%) correlated with increased inbreeding effects like a high percentage of empty seeds. Diversity parameters calculated as averages across the analysed loci should always be completed with the calculation of effective population sizes considering sibship structures based on multilocus genotypes. The combined approaches are an improved basis for drawing practical conclusions. We recommend that the current regulations for forest reproductive material should be adapted. For wind-pollinated stand-forming tree species a minimum number of 100 adult trees should be required to form approved seed stands in the category "Selected". [ABSTRACT FROM AUTHOR]

• Study of seepage water under pure and mixed stands of Douglas fir, spruce and beech. • Seepage water under beech: largest amount and lowest NO 3 , Ca, Mg, Al concentration. • Seepage water under Douglas fir: smallest amount. • Seepage water under Douglas fir at N-rich sites: high NO 3 , Ca, Mg, Al concentration. • Mixed Douglas fir–beech stands: good option concerning water quantity and quality. Norway spruce (Picea abies L.) has been a key tree species and timber source in European forests the last centuries and is increasingly suffering from drought and bark beetle infestations due to climate warming. Current management options include replacing of Norway spruce monocultures with pure and mixed stands of European beech (Fagus sylvatica) that is the naturally dominating tree species in Central Europe. Additionally, Douglas fir (Psudotsuga menziesii), a tree species with high water use efficiency and drought tolerance, is being increasingly cultivated to increase the resilience of European forests and meet the future demand of conifer timber in a warming climate. We studied the seepage water quantity and quality with a particular focus on the nitrate (NO 3 –) concentration and N leaching under pure and mixed stands of Douglas fir, Norway spruce, and European beech at seven sites in Germany. Additionally, we investigated seepage water concentrations of SO 4 -S, Ca, Mg, K, Al and hydrological variables (interception, canopy throughfall, transpiration). Looking at the seepage water quantity and quality, the best management option is the cultivation of pure beech stands. However, this is associated with the well-known risk of monocultures concerning ecosystem disturbance. Beech stands showed the highest seepage water quantities and the lowest seepage water concentrations of major cations and anions, including NO 3 –. Seepage water quantity was the smallest under pure Douglas fir compared to spruce and beech stands. The composition effects of stand tree species on seepage water quality and nutrient leaching were site-dependent. At N-rich sites, pure Douglas fir stands showed higher seepage water NO 3 – concentrations than spruce and beech stands, whereas the tree species effects were small at N-poor sites. With respect to seepage water quantity and quality, cultivation of mixed Douglas fir–beech stands is a promising option for producing conifer timber and at the same time avoiding increased disturbance risks of mono-species forests under a warmer climate. Our results support the recommendation of mixed Douglas fir–beech stands based on soil quality, ecosystem resilience, and forest economic studies. [ABSTRACT FROM AUTHOR]

Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] is an economically valuable non-native tree species in Germany and is considered very promising in view of global climate change. Therefore, the genetic characterization of Douglas-fir populations and seed stands in Germany is essential. We studied coastal and interior Douglas-fir varieties, both present in Germany, by using eleven isoenzyme and four microsatellite loci. By analyzing eight reference populations of known origin we were able to identify the two varieties on the population level using Bayesian and distance based methods. Seven populations present in Bavaria were then successfully assigned to one of the two varieties. Within varieties we found stronger grouping within the interior variety than within the coastal one. Despite lower differences within coastal Douglas-fir, we have first indications for the origin of two populations. For two Bavarian populations, natural regeneration was included and genetic data revealed no significant genetic difference between adults and offspring. The parentage analysis for one of the studied stands revealed that a large proportion of adults took part in the reproduction, but some trees were more successful than others in transferring their genes to the next generation. Our study was able to improve variety identification of Douglas-fir using isoenzyme markers and nuclear microsatellites and study reproductive patterns; both are important issues for the management of Douglas-fir stands in Bavaria. [ABSTRACT FROM AUTHOR]

Provenance-specific variation in bark thickness in Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) is important for accurate volume calculations and might carry ecological implications as well. To investigate variation, diameter at breast height (dbh) and double bark thickness (dbt) were measured in 10 experiments in southwestern Germany (16 American and six German seed sources), which were approximately 50 years old and ranged in productivity. Provenance-specific mixed models for dbt versus dbh varied considerably with respect to intercept and slope. Likewise, analysis of covariance on bark ratio (range = 8.0% to 13.2%) with dbh as the linear predictor revealed significant differences ( p < 0.05 to p < 0.0001) in 70% of the comparisons. Influence of seed origin on bark ratio was analyzed for our 16 American sources plus six provenances reported from New Zealand tests. In linear regressions, single geographic position variables explained only a small proportion of the variation in bark ratio (range of r2 = 0.01-0.33), and the same was true for individual climate variables. In contrast, physiographic regions significantly ( p = 0.0013) explained considerable variation ( r2 = 0.66). Likewise, a combination of three climate variables (temperature, frost days, precipitation) proved significant ( p < 0.0001; r2 = 0.87). As bark ratio was inversely related to precipitation at the seed origin, it is inferred that historic fire regimes may have played a selective role in the process by which Douglas-fir allocates dry matter between bark and wood. [ABSTRACT FROM AUTHOR]

Abstract: Epigaeic arthropods were studied in intermediate-aged pure plantations of the exotic American Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) and of European sessile oak (Quercus petraea Liebl.), which had both been established after forest clear-cuts. Studies took place in two blocks in a forest in northwestern Lower Saxony, Germany. Pitfall trapping throughout the vegetation period of 2004 delivered quantitative data for epigaeic macro-arthropods. Communities of ants (Formicidae), ground beetles (Coleoptera: Carabidae) and spiders (Araneae) were studied in further detail. Several differences in catch numbers, species richness and structure of communities became obvious between the studied stands and are partially interpreted as effects of the different tree cover. As far as environmental factors are concerned, the studied Douglas fir stands showed a high cover of mosses and needle litter, a low weed cover, and a higher soil acidity as compared to the sessile oak plantations. Activity of isopods and diplopods was significantly higher within Douglas fir stands than in those of sessile oak, whereas activity of ants, carabids and weevils was lower in the plantations of this exotic tree species. For all three taxa studied in detail, the numbers of exclusively recorded species were higher in oak stands. Except for wolf spiders (Lycosidae), spider communities of sessile oak sustained to a certain degree in the Douglas fir plantations. On the other hand, communities of ants and carabids were quantitatively impoverished under Douglas fir. Overall, non-metric multidimensional scaling (NMDS) and cluster analysis showed that the communities of all three taxa in focus were strongly altered by treatment and by area, with treatment prevailing over area. Furthermore, we expected especially carabid communities to recruit individuals continuously from the surrounding deciduous forests. With some reservations resulting from the few replicates studied we conclude, that (1) intermediate-aged pure Douglas fir plantations are no biodiversity deserts as a broad spectrum of epigaeic arthropods persists in the plantations, at least, when these are small-sized. Furthermore, we conclude that (2) afforestation with exotic Douglas fir leads to conspicuous changes in epigaeic invertebrate communities as compared to autochthonous, deciduous forests of the same age class. Recommendations for forestry using Douglas fir and aimed at conserving biodiversity include the restriction of Douglas fir to recent and new forests, to avoid pure and dense stands, as well as to limit the total area stocked. [Copyright &y& Elsevier]

We investigated ground beetle communities (Coleoptera, Carabidae) in ancient woodland remnants in north-western Lower Saxony, Germany. A total of 90 pitfall traps was exposed in a stratified design in 10 stands of mature oak–beech and oak–hornbeam forests in the year 2003. Overall, 47 species (10,676 individuals) were recorded. Among these were the two relict species Carabus glabratus and Abax parallelus, and 14 further eurytopic forest species. Eleven species exhibited a high frequency and were found in all of the ten stands. Multiple linear regressions showed several significant relationships at two scales for species richness of different groups of carabids and for several of the measured environmental factors. Forest area, litter depth, amount of dead wood, distance to forest edge, and soil moisture were found to be key factors determining species richness. Furthermore, recent disturbance by logging reduced the number of forest species. According to direct gradient analyses soil moisture and litter depth have greatest influence on species communities of both, forest species and widespread species. Habitat suitability models for the two recorded relict species, A. paralellus and C. glabratus, were developed using logistic regression. The presence of A. parallelus in the mature ancient woodland remnants depends mainly on higher values of soil moisture, whereas for C. glabratus none of the measured environmental variables appeared to be key factors. Implications for the conservation of carabid assemblages in mature ancient woodlands include the advice to spread out logging over long periods of time and over various woodlands in order to keep the stand disturbance at a long-term low level. Variation in logging practices may help to conserve diverse structures. Afforestation with non-native tree species should be avoided in the managed ancient woodlands. Finally, especially the preservation of a high soil moisture seems to be important to conserve typical carabid communities. [ABSTRACT FROM AUTHOR]

Key message: A fully automated algorithm allowed knot detection and positioning on computed tomography (CT) images of Douglas-fir logs. The detection of knot diameter and status could benefit from further improvements, i.e., testing other configurations and implementing texture measures. Manual measurement on CT images allows for tridimensional assessment and greater attainable sampling, while manual measurement on discs provides additional color and texture information. Context: Computed tomography (CT) is a very successful tool to non-destructively acquire the internal knot structure of a log. To enable large-scale applications, an algorithm that automatically detects knots is required. The accuracy of such algorithms depends heavily on the species and image resolution. Aim: This study validates a knot detection algorithm (Johansson et al. in Comput Electron Agric 96:238–45, 2013) on fresh Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) logs. Methods: In this study, 282 knots were sampled from 15 logs, selected from six 78-year-old trees in southwest Germany. The validation of the algorithm's knot detection was performed via comparison against two manual methods: on physical samples and on CT images. Results: The saturated sapwood negatively influences the overall knot detection, which causes underestimation of knot diameter in this area or incomplete detection. The algorithm tended to overestimate knot diameter, longitudinal position, and knot length. Conclusion: The algorithm provides the knot position with satisfactory accuracy. Other settings on contrast and considered volume around a knot can be tested within the algorithm, as well as new development and implementation of texture measures in the image analysis to improve the accuracy results for Douglas-fir in future investigations. [ABSTRACT FROM AUTHOR]