Level of invasion and invasibility of European habitats, assessed on the basis of large phytosociological databases

Chytry, Milan; Pysek, Petr; Jarosik, Vojtech; Maskell, Lindsay; Pino, Joan; Vila, Montserrat; Wild, Jan; Font, Xavier; Smart, Simon; Hajek, Ondrej; Knollova, Ilona; Tichy, Lubomir; Danihelka, Jiri. 2008 Level of invasion and invasibility of European habitats, assessed on the basis of large phytosociological databases. [Speech] In: 17th International Workshop. European vegetation survey. Using phytosociological data to address ecological questions, Brno, Czech Republic, 1-5 May 2008. Brno, Czech Republic, Masaryk University, 26.

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Habitats vary considerably in the level of invasion (LI), i.e. the number or proportion of alien plant species. To determine typical LIs for different habitats, we compiled a database of 52 480 relevés from three contrasting regions: Catalonia, Czech Republic and Great Britain. We classified plants into neophytes, archaeophytes and native, and calculated the proportion of each group in 33 EUNIS habitats. Only 8 of 545 aliens found in the relevés occurred in all three regions. Despite this large difference in alien species composition, habitat LIs were consistent among regions. Few aliens were found in nutrient-poor habitats, e.g. mires, heaths and alpine grasslands. Many aliens were found in frequently disturbed habitats with fluctuating nutrient availability, e.g. in man-made habitats. Neophytes were also frequently found in coastal, littoral and riverine habitats. Besides local habitat properties LI depends on propagule pressure of aliens. To determine real susceptibility of habitats to invasions (invasibility), it is necessary to factor out the effects of propagule pressure on the LI. We did it by statistical modelling based on phytosociological data and digital maps. Using regression trees, the proportion of aliens was related to variables representing habitat properties, propagule pressure and climate. Propagule pressure was expressed through urban, industrial or agricultural land cover and human population density in the region. Urban and industrial land use positively affected the proportion of both archaeophytes and neophytes. Agricultural land use and higher population density positively affected the proportion of archaeophytes. After removing the propagule pressure effect, some habitats with intermediate LI had very low relative proportions of aliens. This indicates that these habitats, e.g., dry, wet and saline grasslands, base-rich fens or deciduous forests are invasion-resistant. Overall, habitats explained much more variation in the LI than propagule pressure. Our findings that (1) habitat LIs are consistent across contrasting parts of Europe, and (2) LI mainly depends on habitat type and less so on propagule pressure, enabled us to extrapolate our data to wider Europe. By plotting the quantitative information on the LIs from Catalonian, Czech and British data on the CORINE land cover map of Europe, we produced the first European LI map.

Item Type: Publication - Conference Item (Speech)
Programmes: CEH Programmes pre-2009 publications > Biodiversity > SE01A Sustainable Monitoring and Management of Land Resources > SE01.2 Countryside Survey 2007
UKCEH and CEH Sections/Science Areas: Parr
Additional Information. Not used in RCUK Gateway to Research.: Abstract
NORA Subject Terms: Botany
Ecology and Environment
Related URLs:
Date made live: 28 Apr 2009 09:52 +0 (UTC)

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