Relationship between the distribution of Phellodendron amurense and environmental factors in the Beijing area

Amur cork (Phellodendron amurense Rupr.) is listed as a second-class protected plant, and is found in small populations of scattered broad-leaved forests in the Beijing area. A total of 12 plots (20 m×20 m) were set up in Baihuashan, Songshan, and Wulingshan Nature Reserves in Beijing to understand the relationship between the distribution of P. amurense and environmental factors in Beijing and to promote population development. The CCA method was used to analyze the effects of different locations, and the relationship between the growth and distribution of P. amurense and 11 environmental factors such as altitude, slope, aspect, canopy density, soil pH, soil available N, and soil organic matter. Results showed that the first axis of the CCA ordination diagram mainly reflected changes in altitude, canopy density, and slope, whereas, the second axis mainly reflected changes in organic matter content, nitrogen content, pH value, and slope. Thus, altitude, soil available N, and soil organic matter are important environmental factors that influence Amur cork distribution, and areas with low altitude, low soil available N and high soil organic matter are suitable for its growth. Quantitative analysis of the influence of environmental factors on species distribution showed they had a good ability to explain P. amurense distribution (84.5%) and a good sorting effect, suggesting that the distribution of amur cork in the sample spots was strongly affected by the studied environmental factors. The plant community also showed a corresponding relationship with areas exhibiting less human interference. There was a significant correlation between environmental factors and species distribution (P=0.03), which strengthened the reliability of the results.