Dynamic Structural Changes in a Population of Rhododendron huadingense, a Rare and Endemic Species in Zhejiang, East China.

Rhododendron huadingense is a nationally protected wild plant species in China with a small population and narrow natural distribution, which is experiencing severe anthropogenic threats. The demographic structure and trends of R. huadingense on Mount Dapan in Zhejiang Province were analyzed to help researchers understand its population dynamics by using static life tables, quantitative dynamic indices, survivorship curves, and survival analysis based on three censuses of a 1 ha plot in 2012, 2017, and 2022. Over this decade, the population of R. huadingense declined by 9.58% from 668 to 604 individuals. From 2012 to 2022, the diameter class structure of the population consistently exhibited a pyramidal pattern, with the number of individuals initially increasing and then decreasing as diameter classes advanced. Over this decade, the diameter class structure of the population consistently showed a declining trend. Dynamic indices showed that the quantitative dynamic index of the population without external interferences was greater than with external interferences, and that both were greater than zero, suggesting growth potential. The maximum risk probability in response to random disturbance from 2012 to 2022 (2017 > 2022 > 2012) was greater than zero but relatively small, indicating underlying demographic instability. Life tables showed Deevey Type II survivorship with mortality rates decreasing in larger diameter classes. These demographic patterns indicate that R. huadingense is transitioning from recruitment-driven growth to senescence-dominated population dynamics. Urgent conservation interventions are needed, including (1) enhancing seedling establishment, (2) improving habitat quality, (3) promoting natural regeneration processes.