The study was conducted near the Yellow Sea State Forest Park in a coastal area of Yellow Sea in Dongtai County, northern Jiangsu Province, eastern China (32°33–57′N, 102°07′E). The monsoon climate influences the study area. It is located in the transition zone from a north subtropical to warm temperate climate. Annual mean temperature, rainfall and relative humidity are 13.7 °C, 1051 mm and 88.3%, respectively. The 220 d yr−1 frost-free period compliments the average sunshine hours of 2169.6 h yr−1. The study site lies along the lower reaches of the alluvial plain of the Yangtze River and has desalted meadow sandy loam soil with 1.4% soil organic matter. Dongtai County sits at the center of the distribution of poplar forests and supports 3000 ha of plantations. A 4-yr-old stand of pure poplar plantations (Populus deltoides) with undergrowth vegetation mainly comprised of Humulus scandens and Pteris biaurita was selected as the study site. The afforestation density of poplar was 3 m × 5 m. In the study area, the forest canopy coverage was 72%, and the mean tree height was 18.1 m with a mean diameter at breast height (DBH) of 16.2 cm.