The mechanisms governing community assembly is fundamental to ecological restoration and clarification of the assembly processes associated with severe disturbances (characterized by no biological legacy and serious environmental problems) is essential. However, a systematic understanding of community assembly in the context of severe anthropogenic disturbance remains lacking. Here, we explored community assembly processes after metal mining, which is considered to be a highly destructive activity to provide insight into the assembly rules associated with severe anthropogenic disturbance. Using a chronosequence approach, we selected vegetation patches representing different successional stages and collected data on eight plant functional traits from each stage. The traits were classified as establishment and regenerative traits. Based on these traits, null models were constructed to identify the processes driving assembly at various successional stages. Comparison of our observations with the null models indicated that establishment and regenerative traits converged in the primary stage of succession. As succession progressed, establishment traits shifted to neutral assembly, whereas regeneration traits alternately converged and diverged. The observed establishment traits were equal to expected values, whereas regenerative traits diverged significantly after more than 20 years of succession. Furthermore, the available Cr content was linked strongly to species' ecological strategies. In the initial stages of vegetation succession in an abandoned metal mine, the plant community was mainly affected by the available metal content and dispersal limitation. It was probably further affected by strong interspecific interaction after the environmental conditions had improved, and stochastic processes became dominant during the stage with a successional age of more than 20 years.

Background: Variations in phenotypic traits of various plants living in either normal or stressed environments have been well studied, but ecological responses of plants to long-term persistent toxic metal pollution have little been reported. In this study, in order to explore the effects of continuous metal pollution in soil on variation and differentiation in the plants, Rumex crispus L. populations exposed to different levels of long-term persistent toxic metal pollution were studied, and corresponding R. crispus populations that had not been exposed to pollution were used as controls. Results: Six phenotypic traits of R. crispus—root diameter, leaf area, leaf length, leaf width, leaf perimeter, and leaf length-to-width ratio—differed significantly among and within populations. Traits ranked in descending order of coefficient of variation were leaf area, leaf perimeter, root diameter, leaf length, leaf width, leaf length-to-width ratio. The average coefficient of variation was 46%. Phenotypic variation in R. crispus was much greater among populations (92.69%) than within populations (6.55%). The mean phenotypic differentiation coefficient (Vst) of 93.37% indicates that the interpopulation variability was the main source of phenotypic variation in R. crispus. Finally, root diameter was significantly positively correlated with metal factors, but leaf area, leaf length, and leaf aspect ratio were significantly negatively correlated with Pb, Zn, Mn, and Fe contents. Overall, underground growth is superior to aboveground growth in populations that have experienced long-term exposure to toxic metal pollution, and there were phenotypic differences between uncontaminated and contaminated populations. Conclusions: These results indicate that R. crispus adapts to the heterogeneous environment caused by toxic metal pollution through rich phenotypic variation, and ecological differentiation has occurred among different populations.