ALIEN PLANTS IN TEMPERATE WEED COMMUNITIES: PREHISTORIC AND RECENT INVADERS OCCUPY DIFFERENT HABITATS

摘要: Variables determining the number of native and alien plants on arable land in Central Europe are identified. Species richness 698 samples weed floras recorded Czech Republic plots a standard size 100 m 2 1955-2000 was studied relation to altitudinally based floristic region, soil type, type cultivated crop, climatic variables, altitude, year record, crop cover height, human population density region. Vascular plant species were classified into alien, latter divided archaeophytes, introduced before AD 1500, neophytes, after this date. The use minimal adequate models analysis covariance allowed determination net effects mutually correlated environmental variables. Models for particular groups explained 33-48% variation numbers 27-51% propor- tions; however, explanatory variables affected species, neophytes differently. proportion increased 1955-2000, whereas archaeophytes declined (in more slowly warm than moderate cool altitudinal region). In dry regions soils, where most find optimum conditions, fewer able persist communities colder wetter regions. Archaeophytes respond like some (climate, seasonal development crop) alternatively other (increasing agricultural intensification through time, density). common old crops intro- duced with beginning agriculture (cereals), but poorly represented relatively recently (rape, maize), numerous. These patterns reflect history invasions Europe. Neolithic agriculture, from Near East sixth millenium BC, brought and, by creating intense continuous propagule pressure imposing new man- agement, facilitated their invasion. By contrast, during past five centuries specific agrotechnical management have supported spreading mainly invaders overseas.