[Optimization of application parameters of soil seed bank in vegetation recovery via response surface methodology].

The thickness of surface soil, the covering thickness and the number of adding arbor seeds are all important factors to be considered in the application of soil seed bank (SSB) for vegetation recovery. To determine the optimal conditions, the Box-Behnken central composite design with three parameters and three levels was conducted and Design-Expert was used for response surface optimization. Finally, the optimal model and optimal level of each parameter were selected. The quadratic model was more suitable for response surface optimization (P < 0.0001), indicating the model had good statistical significance which could express ideal relations between all the independent variable and dependent variable. For the optimum condition, the thickness of surface soil was 4.3 cm, the covering thickness was 2 cm, and the number of adding arbor seeds was 224 ind x m(-2), under which the number of germinated seedlings could be reached up to 6222 plants x m(-2). During the process of seed germination, significant interactions between the thickness of surface soil and the covering thickness, as well as the thickness of surface soil and the number of adding arbor seeds were found, but the relationship between the covering thickness and the number of adding arbor seeds was relatively unremarkable. Among all the parameters, the thickness of surface soil was the most important one, which had the steepest curve and the largest standardized coefficient.

[Topsoil application in vegetation restoration in Japan].

Soil seed bank has the unique regional species composition and genetic characteristics, and plays important roles in maintaining species diversity and population density. Topsoil, as a kind of revegetation materials, has the potential in vegetation restoration. Based on the Japanese literatures, this paper introduced the characteristics and contents of revegetation with topsoil, and discussed the revegetation modes from the aspects of topsoil mixing ratio, slope surface condition, and topsoil collection depth. The application cases of topsoil in various habitat types such as forests, roads, wetlands, and abandoned lands were also introduced. Some suggestions to the further researches on topsoil application in vegetation restoration were proposed, e.g., to strengthen the practical research of topsoil, to determine the appropriate techniques and targets of topsoil application as well as the survey methods and applicability standards, and to develop the low cost and high-efficient new application ways of topsoil.