title: Functional traits contributed to the superior performance of the exotic species Robinia pseudoacacia: a comparison with the native tree Sophora japonica.
abstract: Functional traits determine the ecological strategies of plants and therefore are widely considered to feature in the success of invasive species. By comparing a widespread exotic invasive species Robinia pseudoacacia L. with a related native one Sophora japonica L., this research aimed to study strategies of R. pseudoacacia for superior performance from the perspective of functional traits. We conducted a greenhouse experiment in which seedlings of R. pseudoacacia and S. japonica were grown separately under a factorial combination of two light regimes and three levels of nitrogen (N) fertilization, including a control and two levels intended to represent ambient and future levels of N deposition in Chinese forests. After 90 days of treatment, performance and functional traits were determined for the two species, the former referred to as the total biomass (TB) that directly affected fitness. Trait plasticity and integration (the pattern and extent of functional covariance among different plant traits) were analyzed and compared. We found that the two species showed significantly different plastic responses to light increase: in the low-light regime, they were similar in performance and functional traits, while in the high-light regime, R. pseudoacacia achieved a significantly higher TB and a suite of divergent but advantageous functional traits versus S. japonica, such as significantly greater photosynthetic capacity and leaf N concentration, and lower carbon-to-N ratio and root-to-shoot ratio, which conferred it the greater performance. Moreover, across the light gradient, R. pseudoacacia showed higher correlations between photosynthetic capacity and other functional traits than S. japonica. In contrast, N deposition showed little impact on our experiment. Our results suggested that across light regimes, three aspects of functional traits contributed to the superior performance of R. pseudoacacia: functional trait divergence, significantly different plasticity of these traits, as well as greater overall trait coordination.
authors.affiliation: Institute of Ecology and Biodiversity, School of Life Sciences, Shandong University, 27 Shanda Nanlu, Jinan 250100, China Shandong Provincial Engineering and Technology Research Center for Vegetation Ecology, Shandong University, 27 Shanda Nanlu, Jinan 250100, China.
authors.forename: Yujie
authors.initials: Y
authors.lastname: Luo
authors.affiliation: School of Forestry, Shandong Agricultural University, 61 Daizong Street, Taian 271018, China.
authors.forename: Yifu
authors.initials: Y
authors.lastname: Yuan
authors.affiliation: Institute of Ecology and Biodiversity, School of Life Sciences, Shandong University, 27 Shanda Nanlu, Jinan 250100, China Shandong Provincial Engineering and Technology Research Center for Vegetation Ecology, Shandong University, 27 Shanda Nanlu, Jinan 250100, China Institute of Environmental Research, Shandong University, 27 Shanda Nanlu, Jinan 250100, China.
authors.forename: Renqing
authors.initials: R
authors.lastname: Wang
authors.affiliation: Institute of Environmental Research, Shandong University, 27 Shanda Nanlu, Jinan 250100, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Liu
authors.affiliation: Institute of Ecology and Biodiversity, School of Life Sciences, Shandong University, 27 Shanda Nanlu, Jinan 250100, China Shandong Provincial Engineering and Technology Research Center for Vegetation Ecology, Shandong University, 27 Shanda Nanlu, Jinan 250100, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Du
authors.affiliation: Institute of Ecology and Biodiversity, School of Life Sciences, Shandong University, 27 Shanda Nanlu, Jinan 250100, China Shandong Provincial Engineering and Technology Research Center for Vegetation Ecology, Shandong University, 27 Shanda Nanlu, Jinan 250100, China guo_wh@yahoo.com.
authors.forename: Weihua
authors.initials: W
authors.lastname: Guo
mesh_terms: D018533:Biomass; D058865:Introduced Species; D008027:Light; D016014:Linear Models; D025341:Principal Component Analysis; D019655:Quantitative Trait, Heritable; D031301:Robinia / Q000502:physiology* / Q000528:radiation effects; D029909:Sophora / Q000502:physiology* / Q000528:radiation effects; D013045:Species Specificity; D014197:Trees / Q000502:physiology* / Q000528:radiation effects
keywords: exotic plant invasion; functional trait divergence; light gradient; phenotypic plasticity; species comparison; trait coordination.