Alien plant invasions in European woodlands

Abstract

regions; 1970-2015 time period), we analysed the species pool and frequency of alien vascular plants with respect to geographic origin and life-forms, and the levels of invasion across the European Nature Information System (EUNIS) woodland habitats. Results:We found a total of 386 alien plant species (comprising 7% of all recorded vascular plants). Aliens originating from outside of and from within Europe were almost equally represented in the species pool (192 vs. 181 species) but relative frequency was skewed towards the former group (77% vs. 22%) due, to some extent, to the frequent occurrence of Impatiens parviflora (21% frequency among alien plants).Phanerophytes were the most species-rich life-form (148 species) and had the highest representation in terms of relative frequency (39%) among aliens in the dataset. Apart from Europe (181 species), North America was the most important source of alien plants (109 species). At the local scale, temperate and boreal softwood riparian woodland (5%) and mire and mountain coniferous woodland (<1%) had the highest and lowest mean relative alien species richness (percentage of alien species per plot), respectively. Main conclusions:Our results indicate that European woodlands are prone to alien plant invasions especially when exposed to disturbance, fragmentation, alien propagule pressure and high soil nutrient levels. Given the persistence of these factors in the landscape, competitive alien plant species with a broad niche, including alien trees and shrubs, are likely to persist and spread further into European woodlands. K E Y W O R D SEUNIS, exotic, forest, invasive plants, life-form, neophyte, non-native, origin, tree | INTRODUCTIONGlobalization has triggered a massive spread of plant species to areas outside their native distribution ranges (van Kleunen et al., 2015).Some alien species persist only temporarily as casuals in the new area, while others can overcome local abiotic and reproductive barriers to establish self-sustaining populations (Richardson et al., 2000). Some naturalized aliens become invasive, that is they can spread in large numbers and across considerable distances (Richardson et al., 2000) or can have detrimental environmental and socio-economic impacts Woodlands cover a third of Europe's terrestrial area (Forest Europe, 2015; note that we use "woodland" as a synonym of "forest" in our article). In the past, they were logged and transformed to cropland andother open landscape types on a massive scale (Behre, 1988). Today, most European woodlands are composed of stands where the mean tree age is only 60 years (Vilén et al., 2012). Woodlands-and stands with old trees in particular-are generally thought to be resistant to alien plant invasions given the specific abiotic conditions in their herb layer, such as a dense canopy cover and a thick litter layer (Rejmánek, 2015). However, an increasing number of studies has questioned this assumption (e.g., Essl, Mang, & Moser, 2012;Kohli, Jose, Pal Singh, & Batish, 2009;Martin, Canham, & Marks, 2009;Re...

Landscape‐scale vegetation homogenization in Central European sub‐montane forests over the past 50 years

“…The single significantly expanding non‐native species was Digitalis purpurea , but its occurrence is still restricted to the southeast part of the region under study. This local result is comparable with the Central European situation in general, where the mountain and sub‐montane forests are less invaded than forests in lowlands (Wagner et al., ).…”

Evaluating differences in the shape of native and alien plant trait distributions will bring new insights into invasions of plant communities

“…Even in less invaded ecosystems, assessment of multiple plots within the same habitat can record sufficient native and alien species to analyse distribution shape, for instance Australian grasslands (He & Lamont, 2008), and urban habitats (Loewenstein & Loewenstein, 2005) as well as coniferous forests (Freeman et al, 2007) in the USA. Where individual habitats are infrequently invaded, it may be possible to aggregate species across a number of such habitats as long as they are representative and phytosociologically equivalent, for example woodlands (Wagner et al, 2017), sand dunes (Carboni, Santoro, & Acosta, 2010) and wetlands (Campos, Biurrun, Garcia-Mijangos, Loidi, & Herrera, 2013) in Europe.…”

Similar Impacts of Alien and Native Tree Species on Understory Light Availability in a Temperate Forest

“…These species covered most of the temperate forests of Central Europe, excluding wetland and riparian forests [45]. The study design was developed to cover the most frequent alien species in European woodlands [46], i.e., P. serotina, Q. rubra, and R. pseudoacacia.…”