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Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) was first introduced to Europe from North America more than 150 years ago, was then planted on a large scale and is now the economically most important exotic tree species in European forests. This literature review summarizes the current knowledge on the effects of Douglas fir on soil chemistry, p...
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... The concept of soil nutrient facilitation has been observed for mixed forests as reported by several authors (Binkley and Giardina, 1998;Comerford et al., 2006;Foster and Bhatti, 2006;Lambers et al., 2008;Rakshit et al., 2015;Schmid et al., 2014). Nutrient facilitation plays a crucial role in increasing the productivity of mixed stands compared to pure stands (Ammer, 2019). ...
The establishment of mixed forest stands is an option to enhance soil organic carbon stocks and to protect forest ecosystems from various impacts of climate change. Increasing temperatures and drought potentially affect the vitality of the native coniferous Norway spruce (Picea abies), often used in mixed forests. We investigated the effects of a replacement of Norway spruce by Douglas fir (Pseudotsuga menziesii) admixed to European beech (Fagus sylvatica) on carbon (C) and nitrogen (N) concentrations and stocks, as well as the vertical distribution and changes in forest floor and mineral soil (down to 30 cm depth). Two regions with different soil conditions (loamy vs sandy soils textures) were selected, considering four sites in each region. Each site included a quintet of neighboring forest stands (>85 yrs) of European beech, Douglas fir, and Norway spruce stands as well as mixtures of beech with either Douglas fir or spruce. Our results showed that the C stocks of the organic layer were significantly influenced by tree species, while the C stock of the mineral soil varied among soil types. Total soil organic C stocks demonstrated notable species-specific characteristics, primarily driven by the elevated C stocks in the organic layer. In sandy soils, conifers and mixed forests store 10 % more C and N in the organic layer compared to loamy soils, whereas the C and N stocks under beech remained unaffected, regardless of the site condition. The interaction between species and sites was significant only for Douglas fir and mixed Douglas fir/ beech, indicating that the impact of species on C and N varied across sites and was notably pronounced in sandy soils. The higher potential for carbon and N storage in mixed-species forests compared to pure stands emphasizes the capacity of mixed forests to provide valuable ecosystem services, enhancing C sequestration in sandy soils.
... into European forests is receiving increasing attention (Bolte et al., 2009;Schmid et al., 2014). ...
Forest soils are a critical component of terrestrial ecosystems and host a large number of animal decomposer species. One diverse and abundant decomposer taxon is oribatid mites (Acari: Oribatida), whose species composition varies with forest type and tree species composition. We used functional traits that indicate different niche dimensions, to infer assembly processes of oribatid mite communities in monocultures and mixed forests of native and introduced tree species. We found that coexisting species differed more in the resource‐related niche dimension, i.e., reproductive mode and trophic guild, than in the morphological dimension, e.g., body length and width, sclerotization and concealability. These results suggest that both filtering and partitioning processes structure oribatid mite communities. In native European beech forests, but not in non‐native Douglas fir forests, oribatid mites were mainly structured by filtering processes acting via traits related both to environmental tolerance and to resources. Furthermore, oribatid mite trait diversity, but not phylogenetic diversity, differed significantly between monocultures and mixed forests, demonstrating that multidimensional diversity indices provide additional information on soil biodiversity. Overall, the study provides evidence that traits representing different niche dimensions need to be considered for understanding assembly processes in soil animal communities and thereby soil biodiversity.
... Na široké řadě stanovišť předčí svou objemovou produkcí naše domácí hospodářské dřeviny (Kantor 2008;Kantor, Mareš 2009;Tauchman et al. 2010;Podrázský et al. 2013;Kubeček et al. 2014;Mondek, Baláš 2019;Remeš et al. 2020) a poskytuje velmi kvalitní dřevní surovinu (Zeidler et al. 2022). Její vliv na biodiverzitu domácí podrostní flóry je malý až zanedbatelný (Thomas et al. 2022;Glatthorn et al. 2023), ačkoli její působení na faunu je méně probádané a spekuluje se o možném negativním vlivu na ornitofaunu (Schmid et al. 2014). Douglaska také příznivěji ovlivňuje půdu v porovnání s domácími jehličnatými dřevinami (Ulbrichová et al. 2014;Podrázský et al. 2020; Thomas et al. 2022), může ale také zvyšovat nitrifikaci Matějka et al. 2015;Zeller et al. 2019;Podrázský et al. 2020; Thomas et al. 2022). ...
The article focuses on the growth response of young stands of Douglas-fir and mixtures of Douglas-fir with Scots pine on nutrient-poor sites. The experiment was established in a seventeen-year-old naturally regenerated stands using a block design with two replications. The silvicultural intervention (thinning) involved reducing the number of trees to 1,800 per hectare in the stand without pine representation and reducing it to approximately 4,000 trees in the less mature stand in the mixture with pine. The results of a thirteen-year time series since the implementation of the initial thinning are presented. The diameter growth of Douglas-fir on these sites is significantly lower compared to Scots pine. Without thinning, Douglas-fir is gradually being displaced by Scots pine in the stand, leading to a decrease in its representation and basal area. The silvicultural intervention have positively influenced diameter increment and improved the static properties of the trees, as expressed by their height-diameter ratio (HDR). In the thinned plot without pine occurrence, it was even possible to temporarily reduce the HDR values of target Douglas-fir trees. In the thinned plot with pine competition, the rate of HDR increase was only reduced compared to the control.
... Conifer species that are supposedly better adapted to periodic droughts or are not affected by certain pests have been imported from North America to Europe, such as Pseudotsuga menziesii, to some countries in western Europe (e.g., Garillo-Gavilan and Vila, 2010) and Pinus strobus to western and central Europe (Bednář et al., 2016). There are, however, reservations to utilize these species on a wider scale, as there could be risks of invasive pest outbreaks (Schmid et al., 2014;. ...
... Tree microhabitats are important drivers of arthropod assemblages (e.g., Cours et al., 2021;Sallé et al., 2021;Thorn et al., 2016). The reason for the low number of microhabitats in Douglas fir in our study remains unclear, but low diversity and abundance of associated canopy biota, such as birds and fungi, might be a reason for the lower numbers of microhabitats compared with native conifers (Schmid et al., 2014;Schuldt et al., 2022). ...
Averting climate change‐induced forest diebacks increasingly relies on tree species planted outside of their natural range and on the addition of non‐native tree species to mixed‐species forests. However, the consequences of such changes for associated biodiversity remain poorly understood, especially for the forest canopy as a largely understudied forest stratum. Here, we used flight interception traps and a metabarcoding approach to study the taxonomic and functional (trophic guilds) composition and taxon richness of canopy arthropods. We sampled 15 monospecific and mixed stands of native European beech, native Norway spruce—planted outside its natural range—and non‐native Douglas fir in northwest Germany. We found that the diversity of arthropods was lower in non‐native Douglas fir compared with native beech stands. Taxon richness of herbivores was reduced by both conifer species. Other functional guilds, however, were not affected by stand type. Arthropod composition differed strongly between native broadleaved beech and monospecific coniferous (native spruce or non‐native Douglas fir) stands, with less pronounced differences between the native and non‐native conifers. Beech–conifer mixtures consistently hosted intermediate arthropod diversity and community composition compared with the respective monospecific stands. Moreover, arthropod diversity had a positive relationship with the number of canopy microhabitats. Our study shows that considering arthropod taxa of multiple functional groups reveals the multifaceted impact of non‐native tree species on forest canopy arthropod communities. Contrasting with previous studies that primarily focused on the forest floor, we found that native beech hosts a rich diversity of arthropods, compared with lower diversity and distinct communities in economically attractive, and especially in non‐native, conifers with few canopy microhabitats. Broadleaf–conifer mixtures did not perform better than native beech stands, but mitigated the negative effects of conifers, making such mixtures a compromise to foster both forest‐associated diversity and economic yield.
... Biodiversity effects of Douglas fir outside its natural range in North America are notoriously underresearched, because conifer plantations are usually not very attractive for biodiversity researchers. The few available studies of the effect of Douglas fir on plant diversity mostly refer to even-aged monocultures and only rarely to mixed forests (Budde, 2006;Schmid et al., 2014). Therefore, a knowledge gap exists with respect to gradual changes in biodiversity when increasing proportions of Douglas fir are introduced into semi-natural broadleaved forests. ...
Introduction of drought-tolerant exotic tree species is seen as an important adaptation measure of forest management
to climate change in Central Europe. Douglas fir (Pseudotsuga menziesii) is particularly favored in this
context, because it is adapted to summer droughts due to the climate in its natural distribution range in
temperate western North America and it is also fast-growing and the wood is readily marketable. In Germany,
there are plans to grow Douglas fir on a large scale in mixed forests with other tree species on acidic soils.
Potential ecological consequences have not yet been sufficiently scrutinized. Here, we analyze effects of Douglas
fir introduction into forests of European beech (Fagus sylvatica), which would naturally predominate Central
Europe’s forests. We analyzed vascular plant diversity and species composition of the ground vegetation in a
gradient with increasing Douglas fir canopy fraction that ranged from pure beech (0% Douglas fir) via mixed
stands (25%, 50%, 75% Douglas fir) to pure (100%) Douglas fir forest. Species richness, Shannon diversity, and
Simpson diversity increased with increasing Douglas fir canopy fraction. However, this increase was primarily
driven by an increase of nitrogen-tolerant disturbance indicators, whereas the share of forest species that were
predominant in pure beech forests decreased. Beech forest species declined gradually with increasing Douglas fir
canopy fraction, but these declining species were fewer than the number of species increasing due to Douglas fir
introduction. Cover of ~30% of species remained constant when Douglas fir was introduced. Strong changes in
the ground vegetation were observed at Douglas fir canopy fractions > 40 – 50% and the original character of the
ground vegetation was completely lost beyond a threshold of 75%. Therefore, we discourage from high Douglas
fir proportions beyond these thresholds in production forests and from any introduction of Douglas fir where
nature conservation is a priority.
... Already 20 years ago, Douglas fir was the most extensively planted tree species in France . In Germany, it is likely to become the third most important conifer in addition to the Norway spruce and Scots pine (Schmid et al., 2014). In some German regions, as in the Federal state of Rhineland-Palatinate, the contribution of Douglas fir has reached 17% (Thomas et al., 2015). ...
... Particularly, the Northern American Douglas fir (Pseudotsuga menziesii (MirbeL) Franco) is broadly considered as suitable for Central Europe (Thomas et al. 2022). However, non-native tree species could potentially threaten local biodiversity and ecosystem functioning (Tallamy et al. 2021), calling for research on ecological consequences (Schmid et al. 2014; Thomas et al. 2022). ...
Forest canopies maintain a high proportion of arthropod diversity. The drivers that structure these communities, however, are poorly understood. Therefore, integrative research connecting tree species identity and environmental stand properties with taxonomic and functional community composition of canopy arthropods is required. In this study, we investigated how the taxonomic, functional and trophic composition of arboreal spider communities is affected by tree species composition and associated differences in canopy structure and prey availability in temperate forests. We sampled canopy spiders as well as their potential prey using insecticidal fogging in monospecific and mixed stands of native European beech, native Norway spruce and non-native Douglas fir. Trophic metrics were obtained from stable isotope analysis and structural canopy properties were assessed with mobile laser scanning. Monospecific native spruce stands promoted local canopy spider abundance and diversity, but native beech and beech–conifer mixtures had the highest diversity at landscape scale. Spider community composition differed between monospecific stands, with broadleaf–conifer mixtures mitigating these differences. Irrespective of tree species identity, spider abundance, taxonomic diversity, functional richness and isotopic richness increased in structurally heterogeneous canopies with high prey abundances, but functional evenness and trophic divergence decreased. Our study shows that canopy spiders are differentially affected by tree species identity, canopy structure and prey availability. Broadleaf–conifer mixtures mitigated negative effects of (non-native) conifers, but positive mixture effects were only evident at the landscape scale. Structurally heterogeneous canopies promoted the dominance of only specific trait clusters. This indicates that intermediate heterogeneity might result in high stability of ecological communities.
Supplementary Information
The online version contains supplementary material available at 10.1007/s00442-023-05447-1.
... The effects of alien gymnosperms on the environment in Europe are poorly documented. Most of known evidence comes from studies on P. menziesii, whose impact is similar to that of native conifers (Piwczyński et al., 2016;Schmid et al., 2014). P. strobus, in contrast, is a transformer tree suppressing regeneration of native trees by enormous litter production and root competition (Hadincová et al., 2007). ...
Alien tree species are considered both a threat to nature conservation and a base for forest management. We compiled species occurrences from biodiversity databases, forest inventories, and literature data. We modeled the availability of potential niches using the MaxEnt method and bioclimatic variables for current conditions, 2041–2060, and 2061–2080 periods. We used four climate scenarios: SSP126, SSP245, SSP370, and SSP485. The results confirm our hypotheses that, (i) coniferous species will contract, and deciduous trees will expand their climatic niche, (ii) a significant part of the areas where the studied species currently occur will be outside their climatic optimum in the coming decades; (iii) changes in the climatic optimum distribution will be greater in the 2041–2060 period than in 2061–2080. These predicted shifts are relevant for evidence-based management in sites already occupied by the studied alien trees. Our results are also relevant to the development of prevention and early detection measures in areas predicted to become climatically suitable for the studied species.
... (2) Douglas Fir (DF) is a native tree in temperate regions of western North America and is non-native but widely planted in Europe [22,23]. This tree covered 2-3% of forests in several European countries in 2008 [24] and is found in British Columbia [25]. (3) Ponderosa Pine (PP) trees grow in the driest and warmest zones and are food for a wide range of animals that consume the tree seeds [26]. ...
In the event of an abrupt sunlight reduction scenario, there is a time window that occurs between when food stores would likely run out for many countries (~6 months or less) and ~1 year when resilient foods are scaled up. A promising temporary resilient food is leaf protein concentrate (LPC). Although it is possible to extract LPC from tree biomass (e.g., leaves and needles), neither the yields nor the toxicity of the protein concentrates for humans from the most common tree species has been widely investigated. To help fill this knowledge gap, this study uses high-resolution mass spectrometry and an open-source toolchain for non-targeted screening of toxins on five common North American coniferous species: Western Cedar, Douglas Fir, Ponderosa Pine, Western Hemlock, and Lodgepole Pine. The yields for LPC extraction from the conifers ranged from 1% to 7.5%. The toxicity screenings confirm that these trees may contain toxins that can be consumed in small amounts, and additional studies including measuring the quantity of each toxin are needed. The results indicate that LPC is a promising candidate to be used as resilient food, but future work is needed before LPCs from conifers can be used as a wide-scale human food.
