Abstract
Over 460 non-native (alien) taxa were recorded in a Sefton Coast sand-dune vascular plant inventory, their proportion in the flora increasing after 1999. Between 2005/06 and 2018, twice as many non-native as native plants were found. An analysis of occurrences of native and non-native taxa in six major habitat types found that a higher proportion of aliens was present in scrub/woodland and disturbed ground, while native plants had more occurrences in fixed dunes/dune grasslands, dune heath and wetlands. No differences between the two groups were detected for strandline/shingle and embryo/mobile dune habitats. Twenty-four non-native and 14 native taxa showed invasive characteristics in the duneland. The former included especially Hippophae rhamnoides and Rosa rugosa, both constituting major threats to sand-dune biodiversity. Particularly invasive native plants were Arrhenatherum elatius, Betula spp., Salix cinerea, and Ulex europaea. The main findings accord with studies elsewhere in Britain and Europe showing recent increases of neophytes in semi-natural habitats and that both non-native and native species can have invasive traits. The open habitats of coastal dunes seem to be particularly susceptible to plant invasions.
Highlights
Non-native plants have attracted increasing interest in recent decades
Some species are highly invasive, contributing to globally significant environmental problems (Chytry et al, 2008), while most are “common, conspicuous, pestiferous, beautiful, edible and otherwise useful or harmful” (Stace & Crawley, 2015). The latter authors remarked that alien plants add considerably to a rather limited British flora, contributing 2068 vascular taxa, or 59% of the total
Preston et al (2002) noted a marked increase in the distribution of neophytes in the British Isles from 1930 to 1999, though their analysis probably underestimated the spread, as many species were not mapped in the 1962 Atlas and a “surprisingly large number” had become frequent in Britain
Summary
Non-native (alien) plants have attracted increasing interest in recent decades. Some species are highly invasive, contributing to globally significant environmental problems (Chytry et al, 2008), while most are “common, conspicuous, pestiferous, beautiful, edible and otherwise useful or harmful” (Stace & Crawley, 2015). A more recent analysis of the non-native flora in Northwest England by Greenwood (1999) found a total of 685 taxa for v.c.59, of which 266 (39%) were naturalised and 419 (61%) casuals He pointed to an increasing proportion of nonnative plants in the recorded flora, from 8% before 1830 to 44% between 1930 and 1979, a rate of addition of between one and two taxa per year. The largest sand-dune system in England (2100 ha) is situated on the Sefton Coast, north Merseyside, extending for about 20 km between the estuaries of the Mersey and Ribble It supports an exceptionally rich vascular flora (Smith, 2009) which, by 2008, comprised 1143 vascular taxa of which 405 (35.4%) were introduced (Smith, 2010). An inventory of vascular plants for the Sefton Coast sand-dune system, initially compiled as a draft in 1999, completed in 2005 (Smith, 2006) and updated annually to 2019, provides an opportunity to examine trends in the numbers and proportion of nonnative taxa, including invasive species, together with their preferred habitats, over a time-scale of 20 years
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
