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.

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The extent shape of organisms (body size and the allometry of specific parts) is not only the base for taxonomy, but also the key functional traits for understanding the interaction between organisms and environmental conditions. The geographical variance of body size, allometry, and the underlying mechanisms are fundamental for insect biogeography, but have not been fully documented. In this paper, we compiled data on body size (body length and body width), aspect ratio (body length/body width), and distribution of ladybirds in 28 provinces in China. Meanwhile, we obtained environmental variables representing temperature and precipitation from freely available data. To explore the spatial variance and environmental correlates of body size and aspect ratio in different species groups with various trophic positions, correlation and regression analyses were performed separately on herbivorous and predaceous ladybirds. Our results show that there is evident latitudinal gradient for body size of ladybirds, i.e., body length or width increases with increasing latitude. This is consistent with Bergmann's rule. Temperature-related variables are the main drivers of geographic variance of body size, because ladybirds usually overwinter as adults, and those with larger •研究报告• 776 生 物 多 样 性 Biodiversity Science 第 23 卷