Aim: Alien plant invasion seriously threatens diversity of native plants and ecosystem function. Understanding the underlying mechanisms of plant invasion could help to prevent and control alien plant invasion. Methods: In this study, we selected Ageratina adenophora, an invasive herb invaded in Pinus yunnanensis communities in Panxi region of China, as target species. Based on field investigation, we assessed the effects of environmental factors and community characteristics such as species diversity and phylogenetic diversity on the invasion of A. adenophora. Results: We found that neither environmental factors (i.e. altitude, slope, and fire severity) nor biological factors (i.e. canopy closure and shrub coverage) have significant effect on the intensity of A. adenophora invasion. However, our results demonstrate that the invasion intensity of A. adenophora was significantly impacted by the species diversity of shrub layer (P < 0.05) and the net relatedness index of herb layer to A. adenophora (P < 0.05). Conclusion:The communities with higher species diversity of shrub layer and more closely related to A.

Aims Soil nitrogen (N) availability is the most limiting factor for terrestrial plant growth, and global N deposition can improve the soil N availability. Fast growth may be a general trait of successful invaders, so learning how N addition affected the growth and competitive ability of three Centaurea stoebe populations is conductive to forecasting the plant invasion risk under N deposition. Methods We conducted an experiment simulating N deposition at Chengdu, in which three populations from the invasive forb C. stoebe and one native species Poa pratensis were subjected to two treatments: N addition and ambient. In our study, C. stoebe populations and P. pratensis were planted alone or together, and we determined plant height, leaf area and biomass. Important findings In the absence of competition, N addition promoted the growth of C. stoebe populations, thereby improving their invasive potential to a certain extent. So under the condition of competition, we found that N addition obviously enhanced the competitive effects of C. stoebe on P. pratensis, particularly interspecific root competition. The competitive ability of different populations performed similarly in response to N addition. These results preliminarily suggest that N deposition may increase the potential invasion risks of C. stoebe populations by improving their competitive ability. Key words nitrogen deposition; invasive plants; competitive effects; competitive responses; relative interaction intensity Citation: Peng Y, Peng PH, Li JJ (2016). Simulated nitrogen deposition influences the growth and competitive ability of Centaurea stoebe populations.