Terrestrial Alien Herbs In China

A database of alien flora is important for better understanding the patterns of plant invasion, as well as explicating the mechanisms promoting invasion at local, regional and global scales. And prediction of invasiveness in plants is possible to avoid damage to native ecosystems by exotic species. However, little attention has been paid to the construction of the database of terrestrial alien herbs in China, a risk assessment system for the potential invasiveness does not yet exist in China, and we here make an attempt to integrate sporadic literature and demonstrate the patterns of alien herbaceous species both in chronicle and biogeography, and try to present a rating system to assess the invasion potential of alien terrestrial plants that may become invasive in future.In total,800 herbaceous alien species are identified, belonging to 37 orders and 72 families, ten of which account for 60% of the total flora. The families containing large number of species include Asteraceae, Leguminosae, Cactaceae, Poaceae and Brassicaceae. The species originating from the Americas make up 47% of total species. In relation to life forms, most of the species are perennial herbs (293 species, 40%) and annuals (272 species,37%). About 46% of the species can be often found in the habitats with rich resources and high disturbance. Our results suggest that in China terrestrial alien herbs are distributed throughout the entire country, with particularly high species richness in the Southeast (23%,4 species per ten thousand km2). It is also found that 80% of alien plants were introduced into China intentionally, and there is a steady increase in the number of neophyte species over the last two centuries, of which about 90% were introduced after 1800s and 60% arrived after 1950s. The majority of the alien herbs (524 species, about 71%) are sexual reproduction characteristic, and comparing to the alien non-invasive herbs, the invasive herbs take a high proportion of the asexual vs. sexual mode of reproduction. Regarding flowering traits, the peak flowering season of alien terrestrial herbs is from summer to autumn, and the invasive herbs have a long flowering period than the alien non-invasive herbs.65% of the alien terrestrial plants only can be used in one field. Comparing to alien non-invasive species, the invasive species are consider as more useful. The most frequent economic use is ornamentals identified included 64% of the species, followed by medicinal use (34% of the species). The information on diversity and ecological characteristics of terrestrial alien herbs provided in this paper can be used for designing national management strategies of alien species.Alien species are classified into three categories (high risk, moderate risk, low risk) according to their ecological and biological aspects. The rating system is validated by testing 235 well-known invasive plant species of China and 542 alien plants which have failed to establish themselves in China at large extant. The overall accuracy is 76.8%, the likelihood ratio is 7.3. The accuracy of correctly predicting invasive species is 68.9%, while the accuracy of correctly predicting non-invasive species is 75.3%.51 alien terrestrial plants is classified as high risk.These species should be evaluated carefully by studying the ecology traits to verification whether these species have potential problems.