Effects of the invasive herb Ageratina adenophora on understory plant communities and tree seedling growth in Pinus yunnanensis forests in Yunnan, China.
Understanding the influence of invasive species on understory communities is necessary to maintain ecosystem functions. Here, we describe the effects of different abundances of the invasive species Ageratina adenophora on the composition and structure of understory communities and on Pinus yunnanensis seedling growth under pine stands in mid-Yunnan, China. Our data show that the different abundances of A. adenophora altered species and functional diversity by changing the species composition and abundance in the understory community because of its higher specific leaf area, leaf nitrogen concentration (LNC), and leaf phosphorus concentration compared with native species. Meanwhile, the presence of A. adenophora led to changes in the patterns of species co-occurrence, with a shift from random to segregated patterns as the invasion intensity increased. Furthermore, the order of species loss under invasion was nonrandom. The LNC could be an indicative functional trait predicting the order of species loss, suggesting that species with a lower LNC were lost first with increasing invasion intensity. In addition, a high abundance of the invader A. adenophora suppressed the growth of the seedlings of native canopy trees. Our results indicate that the effect of the invasive herb A. adenophora on the understory community is associated with the nonrandom loss of species with different LNCs and that invasion also suppresses the growth of native canopy dominants.