Geographical distribution and determining factors of different invasive ranks of alien species across China.

Determination of the geographical distribution and life-form spectra of alien species with different invasive abilities are essential to understand the process of invasion and to develop measures tomanage alien species. Based on six classifications of Chinese alien species, environmental and social data, we determined species density, lifeform spectrum of alien species, and the relationship between species density of alien species and climatic or social factors. The species density of alien species increased fromthe northwest to the southeast regions of China for all the six ranks. The boundary line between lowand high species density of alien specieswas consistentwith the dividing line of population density (the "Hu Line"). Mean annual precipitation was themost important factor for species density in malignant invaders, serious invaders, local invaders, and species requiring further observation (Ranks I, II, III, and V, respectively). Gross domestic product per square kilometer and annual minimum temperature were the most important factors in mild invaders and cultivated aliens (Ranks IV and VI, respectively). Annual and biennial herbs made up 52.9% to 71.2% of total species in Ranks I to IV; shrubs and trees 3.7% to 14.7%. The annual and biennial herbswere 35.5% and 32.6%, and the shrubs and treeswere 25.3% and 31.6% in Ranks IV and VI. Results implied that precipitation was themost important factor on species density for the invasive alien species. However, social factors and temperaturewere the most important factors for the non-invasive alien species. The invasive alien species had a high proportion of annual and biennial herbs and non-invasive alien had a high proportion of shrubs and trees. It is important to understand the geographical distribution and life-form spectra of various invasive alien species for alien species controls. (C) 2020 Elsevier B.V. All rights reserved.