Objective Based on the study on the survival pressure intensity of wild Phellodendron amurense in Yanshan Mountains from the aspects of diameter scale, area and vegetation type, a theoretical basis was provided for the protection of rare and endangered species.
Method Twenty-five 20 m × 20 m sample plots were set by the method of typical sampling, and the survival pressure intensity of the wild Phellodendron amurense was analyzed through an individual survival pressure calculating method for rare and endangered tree species.
Result (1) A total of 140 Phellodendron amurense pants were found in this study, scattered in 8 natural reserves, and had the highest density in Beijing Baihuashan National Nature Reserve, the lowest in Hebei Dahaituo National Nature Reserve, with the density of 5.63 plant/m2 and 1.25 plant/m2, respectively; (2) the number of Phellodendron amurense in the small tree stage (I−III diameter scales) was the largest in Yanshan area, with the intraspecific and interspecific competition indices maximally being 13.897 and 48.135, respectively. However, with the increase of DBH, the survival pressure decreased; (3) the highest survival pressure occurred in Hebei Wulingshan National Natural Reserve and the lowest in Hebei Maojingba National Natural Reserve, with the survival pressure of 30.363 and 1.763, respectively; (4) the population of Phellodendron amurense bore a comparably higher survival pressure in Tilia amurensis forest, Juglans mandshurica forest and Phellodendron amurense-Pinus tabuliformis mixed forest, and a lower survival pressure in Ulmus macrocarpa forest, Ulmus macrocarpa-Quercus mongolica-Fraxinus rhynchophylla mixed forest.
Conclusion Interspecific survival pressure plays a major role in the whole population of Phellodendron amurense in Yanshan area. Therefore, it is necessary to prune or selectively cut some tall trees closing to each other and having strong competitiveness, such as Pinus tabuliformis and Juglans mandshurica, in order to reduce the competitive pressure of Phellodendron amurense and promote the regeneration of the natural forest.