(1) 北京林业大学自然保护区学院

Clonal integration is one of the most important traits of clonal plants. It not only can improve the ability of ramets to tolerate environmental stress,but also may influence physicochemical properties of the soil around the ramets. To test the effect of clonal integration on soil properties, we conducted a field experiment in a wetland dominated by Phragmites australis in the Yellow River Delta in China, with clonal integration and crude oil contamination as the two main factors. We added 0,5, or 10 mm thick crude oil per year to circular plots (60 cm in diameter) of the P. australis community to simulate none,moderate,or heavy oil contamination,and kept the rhizome connections between the ramets of P. australis inside and outside the plots severed or not, to prevent or allow clonal integration. The experiment started in 2014. In October 2016,we collected soil samples in the plots and measured soil aggregate composition, pH, electric conductivity, total carbon, total nitrogen, total phosphorus, and organic carbon. Crude oil contamination significantly increased the proportion of large macroaggregates (diameter >2.0 mm),pH, total nitrogen, and organic carbon in the soil, but decreased the proportion of soil microaggregates (diameter: 0.053-0.25 mm) and soil electric conductivity. Clonal integration significantly decreased soil pH, but increased soil electric conductivity, and nitrogen to phosphorus ratio. There was a significant interaction effect between clonal integration and oil contamination only on soil electric conductivity. Therefore, both crude oil contamination and clonal integration can influence physicochemical properties of the soil in wetlands,and the effect of clonal integration on physicochemical properties of the soil around the ramets may further affect the dominance of clonal plants.