Effects of invasive Compositae plants on soil nitrogen content

Biological invasion (incursion of invasive species) destroys the community structure and stability of the ecosystem in the invasion area, hinders the production of agriculture, forestry, animal husbandry and fishery sectors, and endangers human health. China has experienced a high degree of biological invasion, with at least 402 species of invasive plants recorded. A majority of these alien invasive plants are in the families Compositae, Leguminosae, and Gramineae. At least 107 of these species, widely distributed in various provinces in China, are species of Compositae, which are characterized by rapid growth, early maturation period, as well as high seed yield with strong dispersal capacity. We comprehensively analyzed the effect of invasive Compositae species on soil nitrogen content in 211 cases from 38 studies. The results showed that Compositae invasion significantly (P < 0.05) increased soil nitrogen content, in the form of total nitrogen, ammonium, and nitrate, in more than 85% cases, and that Ageratina adenophora is the species that most affects soil nitrogen. We found that invasive Compositae species changed soil nitrogen content and greatly impacted nitrogen resources in the ecosystem by releasing allelochemicals, decomposing litter, and changing the composition and quantity of soil nitrogen cycling microbes. Considering that soil nitrogen is the most important factor limiting plant growth, reviewing the effect of invasive Compositae species on soil nitrogen content will deepen our understanding of the importance of nitrogen in the process of plant invasion and elucidate the invasion mechanism of alien plants.