Effects Of Different Invasive Degrees Of Canadian Goldenrod On The Species Diversity And Functional Diversity Of Native Plant Communities

The co-occurrence of invasive and native plants is a common phenomenon in the native ecosystems.Invasive plants have some functional traits that native piants do not possess.Functional trait is one of the important contents for the research of functional diversity of plant communities currently.Meanwhile,the effects of invasive plants on native plant communities vary with different invasion degrees of the invaders.Therefore,the study aims to address the difference in functional traits between S.canadensis and coexistent native plants across different invasion degrees of S.canadensis and the effects of S.canadensis with different invasion degrees on taxonomic and functional diversity of native plant communities.This study is important to understand the mechanism of the successful invasion of invasive plants S.canadensis.Meanwhile,the results of the present study will also lay a solid theoretical foundation and inform practical applications for the effective prevention and control of S.canadensis invasion.The main results of this study are as following:1.Plant height of S.canadensis increased significantly with increasing invasion degrees of S.canadensis,which can make them obtain more environmental resources(especially the light)during the growing process.2.Plant height,petiole diameter,and leaf width of native plants were significantly higher under heavy invasion of S.canadensis than those under low and moderate invasions of S.canadensis.The reason may be due to that heavy invasion of S.canadensis can pose obvious stress on coexistent native plants,which can improve the competitiveness of native plants via the shifts in their functional traits.3.Plant height,ground diameter,petiole diameter,and leaf thickness of S.canadensis were significantly higher than those of native plants under all invasion degrees of S.canadensis.The taller invader may underlie an advantage of increased resource capture and use(particularly sunlight)and then make a shade on the coexistent native plants to facilitate its further invasion.4.The difference in functional traits between S.canadensis and coexistent native plants under low invasion of S.canadensis supports the habitat filtering hypothesis.With the increase in invasion degrees of S.canadensis,the competition between S.canadensis and coexistent native plants gradually increased,which leads to their niche differentiation.Thus,the difference in functional traits between S.canadensis and coexistent native plants under moderate and heavy invasions mediated by S.canadensis supports the niche differentiation hypothesis.5.Plant taxonomic diversity(i.e.the number of species,Shannon-Wiener diversity index,Simpson dominance index,Pielou evenness index,and Margalef richness index)significantly decreased under heavy invasion of S.canadensis.It may be mainly attributed to the fact that the relative abundance of S.canadensis was significantly higher than coexistent native plants under heavy invasion of S.canadensis,and the competitive advantage of S.canadensis under heavy invasion was higher than that of coexistent native plants.6.Plant functional diversity(i.e.Community weighted mean trait value,Rao’s quadratic entropy,Mason α functional diversity,and Mason β functional diversity)significantly increased under moderate and heavy invasions of S.canadensis.This may be mainly attributed to the fact that many functional traits of S.canadensis with moderate and heavy invasions were significantly higher than those of coexistent native plants,which leads to the differentiation of species niche.Meanwhile,the increase in community functional diversity can make full use of environmental resources and thereby the populations of S.canadensis become more stable,which can facilitate its further invasion process.