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Native range of Douglas-fir with three reference genetic clusters (N-northern cluster, C- central cluster, S-southern) of coastal variety (marked by green) and three reference genetic clusters (N-northern cluster, C- central cluster, S-southern cluster) of interior variety (marked by blue) including reference populations (R01–R39) (a), distribution of studied populations in introduced range (b), distribution of old trees (black circles) and natural regeneration (green circles) in European populations E1–E3 (B1–B3), photographs of old growth in North America and natural regeneration in E3
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Genetic admixture and plasticity along with propagule pressure, large seed dispersal distances and fast adaptation support successful establishment and spread of introduced species outside their native range. Consequently, introductions may display climatic niche shifts in the introduced range. Douglas-fir, a controversial forest and ornamental con...
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Effectively identifying the genetic structure and related factors of a species can facilitate understanding the evolutionary history of the species. Phylogeographic patterns and genetic data are essential in investigating the species historical processes and diversification that response to environmental, climatic and geological influences. In this...
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... Carr., Pseudotsuga menziesii (Mirb.) Franco and Pinus contorta Douglas ex Loudon, all of which are invasive somewhere in Europe or elsewhere in the world (Calviño-Cancela & Rubido-Bará, 2013;Knight et al., 2001;Nuñez et al., 2017;Nygaard & Øyen, 2017;van Loo et al., 2019;Vítková et al., 2017 (Brundu & Richardson, 2016). ...
A large number of non‐native trees (NNTs) have been introduced globally and widely planted, contributing significantly to the world's economy. Although some of these species present a limited risk of spreading beyond their planting sites, a growing number of NNTs are spreading and becoming invasive leading to diverse negative impacts on biodiversity, ecosystem functions and human well‐being. To help minimize the negative impacts and maximize the economic benefits of NNTs, Brundu et al. developed eight guidelines for the sustainable use of NNTs globally—the Global Guidelines for the Use of NNTs (GG‐NNTs).
Here, we used an online survey to assess perceptions of key stakeholders towards NNTs, and explore their knowledge of and compliance with the GG‐NNTs.
Our results show that stakeholders are generally aware that NNTs can provide benefits and cause negative impacts, often simultaneously and they consider that their organization complies with existing regulations and voluntary agreements concerning NNTs. However, they are not aware of or do not apply most of the eight recommendations included in the GG‐NNTs.
We conclude that effectively managing invasions linked to NNTs requires both more communication efforts using an array of channels for improving stakeholder awareness and implementation of simple measures to reduce NNT impacts (e.g. via GG‐NNTs), and a deeper understanding of the barriers and reluctance of stakeholders to manage NNT invasions.
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... This is because including data from the natural range of an invasive species can introduce more bias than not including them. Many studies in forestry, evolutionary biology and biogeography have shown that species exhibit greater variability within their natural ranges than in the areas of introduction or invasion (Dar et al., 2020;Hintsteiner et al., 2018;Neophytou et al., 2020;van Loo et al., 2019). This is because only part of the gene pool is transferred to new areas during migration, and the genetic variability of natural populations is spatially distributed and subject to long-term environmental selection pressures. ...
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.
... Commonly, Douglas fir grows in mixture with other tree species and, occasionally, it forms larger groups or even stands of a few hectares. In Germany and France, the average proportion of Douglas fir stems per hectare is 10 to 15 times higher than in Switzerland because the species is of relatively high economic importance in these countries and has also been planted in monocultures, particularly in France (van Loo et al., 2019;Pötzelsberger et al., 2020b;Bindewald et al., 2021). Douglas fir has been appreciated by European foresters because of its productivity and wood quality for decades. ...
... Douglas fir has regenerated naturally in Europe since the middle of the 20 th century (e.g., OECD, 2008;Schmid et al., 2014;van Loo et al., 2019). By that time Douglas fir, introduced at the end of the 19th century, had reached an age, at which it produced abundant numbers of seeds (Rohmeder, 1972;Annen, 1998). ...
... After successful establishment, however, further development of the seedlings was not affected by the herbaceous vegetation (Knoerzer et al., 1995). A thick litter layer corresponded to a lower probability of finding Douglas fir seedlings, which was probably due to unfavorable germination conditions because litter may act as a mechanical barrier and make it difficult for seedlings to access sufficient water (Caccia and Ballare, 1998;Tschopp et al., 2014). Knoerzer (1999) showed this for Douglas fir germination, especially on sites with a thick needle litter layer. ...
Douglas fir (Pseudotsuga menziesii) has regenerated naturally in European forests since the middle of the 20th century. Some cases of an invasive character of the species have been reported under specific site conditions, but systematic data on the extent of natural regeneration and spread of Douglas fir across different forest communities are largely lacking. Due to its potential tolerance to increasing summer droughts, Douglas fir has been suggested as a sustainable future tree species for Central European forests. In this study, we investigated natural regeneration of Douglas fir in comparison to native tree species in 39 forest stands in Switzerland belonging to different forest communities. We analyzed the regeneration success of Douglas fir, Norway spruce (Picea abies), silver fir (Abies alba), and European beech (Fagus sylvatica) with respect to ecological site conditions. The proportion of Douglas fir seedlings (<130 cm height) was <5% in the majority of stands; but in four stands, Douglas fir was the most abundant species among seedlings. In most other stands, Norway spruce (occurring in 37 stands/dominant in 10 stands), silver fir (38/2 stands) and beech seedlings (35/10 stands) were more abundant than Douglas fir seedlings. Saplings (≥130 cm height but <12 cm diameter at breast height) of Douglas fir were observed in five stands with proportions between 10% and 23% and in eight stands with proportions of <10%, in particular in stands with a high proportion of Douglas fir seed trees. Beech saplings occurred in 28 stands and were most abundant in eleven stands. Saplings of silver fir (24/3 stands) and Norway spruce (19/6 stands) were less frequent. The abundance of Douglas fir seedlings correlated positively with the proximity to seed trees and light transmission of the canopy, but negatively with understory vegetation cover and litter abundance. Ungulate browsing did not significantly affect the regeneration of any tree species in the study stands. On the Central Plateau, Douglas fir was mainly planted in productive beech forest communities where it is strongly limited due to its low competitiveness compared to beech and other fast-growing deciduous tree species. On dry and less productive sites, where the canopy is not closed, Douglas fir is able to establish successfully. On such sites, a close monitoring of Douglas fir regeneration and the potential implementation of control measures is recommended.
In IUFRO experimental plots of 1969–1970, two 'Italian' provenances, I11 and I15, of unknown genetic origins, have consistently exhibited remarkable performance and stability over time and space in previous studies. It was deemed essential to acquire knowledge about the genetic origin area and conduct a genetic characterization of these two Italian provenances for their formal registration. Considering the observed intraspecific genetic variation across the American geographic cline, it was imperative to ensure that the selected provenances adequately represented diverse eco-physiological regions within the species range. To achieve this, most likely American provenances were selected, building upon historical document hypotheses and aiming to cover various geo-climatic areas. Specifically, five coastal variety and three interior variety provenances were chosen, two for each major geo-climatic region. The results obtained, using seven microsatellites, through four genetic structure analysis methods, predominantly attributed I11 to the area around 1080 origin, Washington Cascades region and 1094, Oregon Coast area. Similarly, I15 was primarily attributed to the area around the 1096 provenances, the Oregon Cascades region, compared to other coastal areas it appeared to differ. Among the three interior origins, 1162 from Arizona, Interior South area, exhibited intermediate genetic characteristics between the two varieties, despite its geographical location falling within the range of the interior variety. Similar to our expectations, comparing the distinct characteristics of the origin areas for each Italian provenance, it becomes feasible to complete their certification as 'seed stands' and to plan an appropriate management strategy for the species' diffusion.
Exotic conifer tree species that exhibit more rapid growth and greater timber value than native tree species tend to be selectively grown in plantations. These exotic species are also expected better adapted to climate change. However, some exotic planted species invade neighboring stands, affecting hydrological and nutrient uptake processes among natural tree species. Countermeasures to prevent exotic tree invasion can be costly; therefore, methods for assessing the impacts of introducing exotic tree species are needed. Such methods should evaluate the effects of the water and soil use of exotic tree species, as well as their invasiveness, resilience, and resistance to herbivory. Exotic species have also been studied from the perspective of novel ecosystems. The regeneration and yield of the exotic tree Cunninghamia lanceorata, which has been selected for industrial plantations in Japan, have declined in its country of origin (China) due to allelochemical production. Since tree species in plantations vary in terms of both timber production and social benefits, the effects of these species should be carefully assessed prior to their selection for large-scale planting.
The forest stands of Douglas-fir [Pseudotsuga menziesii (Mirbel) Franco] and Norway spruce [Picea abies (L.) Karst.] in the South Bohemian uplands (Czech Republic) represent an artificial community of a neophyte (native to North America) and indigenous species (with natural distribution in mountain forests). Ecological characteristics of these two tree species and their response to climatic factors were studied using tree ring analyses and correlation of growth indices for tree-to-tree and between trees and historical parameters of climate (average air temperatures, sum of precipitations and relative air humidity). The two datasets were analysed using multidimensional methods. The ordination analysis shows a considerable difference between both tree species. Growth of both species differed significantly by districts and plots. The effect of climate was studied using correlations as floating time-window. Our results showed that average air temperature had a stronger effect on Douglas-fir growth, for which an increment decrease was found at higher temperatures between May 25th and June 24th. Also, the average maximum air temperature affected the growth of Douglas-fir more strongly than that of Norway spruce. More precipitation was associated with a similar positive effect on the growth of both tree species. Air humidity had a significant effect on growth of both studied tree species and the effect of air humidity was more significant than of distinct precipitation. The combined effects of lack of precipitation and high temperature in vegetation period was the major limiting factor for radial growth. Douglas-fir showed higher productivity (+17.2%) and resistance to climate extremes compared to Norway spruce. Our results suggest that a mixed stand could be more resistant in terms of growth stability than mono-specific stands, as the two studied species exhibited different reaction to climate extremes. Our study further showed that mixed stands with high species diversity had a higher production potential (+13.1%).
