Population structure and dynamics of Actinidia arguta in the Yanshan Mountains

Actinidia arguta is an interlayer plant found in forest communities and is a second-class key protected wild plant of China, yet this species has not received adequate attention in previous studies. Comparative study of the vertical pattern of A. arguta in the community in the same mountain range is conducive to the induction of the main causes affecting the population structure and distribution pattern of the species. To explore the growth pattern and population dynamic change of A. arguta, an interlaminar liana plant in the community, the population structure of wild A. arguta in eight national nature reserves in the Yanshan area was investigated using the sample circle method. A specific time life table of A. arguta was compiled and a survival curve was drawn. The results showed that(1) The number of individuals in diameter class I-II(seedling stage) accounted for 15.39%(east section), 31.25%(middle section), and 30.76%(west section) of the total population, all of which were not more than half of the total population. With the increase of diameter class, except for the fluctuation in the west section of Yanshan Mountain, the number of individuals in the middle and east sections decreased gradually and the overall population structure of A. arguta was an "inverted pyramid" type, showing a decreasing trend.(2) The height structure of A. arguta in the survey area conformed to the characteristics of continuous development and was relatively complete. The height structure of the eastern section of Yanshan was generally low, with grade I(< 5 m) accounting for 51.62% and no grade IV(> 15 m) plants; trees were distributed in each height level of the middle section of Yanshan, with grade II height(5-10 m) accounting for 58.80% of the total; no grade IV(> 15 m) plants appeared in the western section of Yanshan; however, the distribution of grade I and grade II(0-10 m) plants was uniform, accounting for 15.38% each, and the third grade(10-15 m) accounted for 69.24%.(3) In the east and middle sections of Yanshan, A. arguta was obviously close to Deevey Ⅱ index function model. In the west section of Yanshan, it was between Deevey Ⅰ and Ⅱ, but was closer to Ⅱ. The survival curve was consistent with the results of the life table. The overall population structure of A. arguta in the Yanshan region showed a declining pattern. As an important germplasm resource in China, A. arguta is widely distributed in the Yanshan area; however, the population is seriously damaged an