Abstract:

Chinese ironwood (Parrotia subaequalis) is classified as a first-class protected plant species in China and represents a rare example of plant species with extremely small populations. The Zhejiang Hynobius amjiensis National Nature Reserve serves as one of the key distribution sites for this critically endangered plant species and is also among the earliest sites to conduct research on P. subaequalis. However, investigations into the population characteristics of P. subaequalis within this reserve remain relatively insufficient, and there has yet to be a systematic exploration of the community characteristics associated with its primary habitat. This study established 22 plots that represent the primary habitat communities for this species within the reserve. Comprehensive investigations were conducted to assess both species composition and quantitative attributes of these communities, alongside an analysis of various community types and their respective characteristics. Furthermore, by examining the diameter class structure, compiling a static life table, drawing a survival curve, and calculating dynamic change indices of the P. subaequalis population, this study explored the intricate aspects of population dynamics concerning P. subaequalis. The results indicated that a total of 1 457 woody plants (including 121 individuals of P. subaequalis) with a diameter at breast height (DBH) of ≥ 1 cm were recorded, representing 106 species from 82 genera across 44 families. The 22 plant communities in their primary habitats were classified into 14 alliances. The population of P. subaequalis exhibited a relatively low proportion of seedlings and saplings with DBH < 7.5 cm, comprising only 22.31% of the total number of individuals. This observation suggests significant challenges regarding population renewal. The species survival curve conformed to the Deevey-II type. Notably, there were significant differences in population dynamic indices between natural and disturbed conditions, revealing an insufficient capacity for the population to withstand external disturbances. In light of these findings, this study recommends enhancing in-situ conservation efforts for P. subaequalis populations within the Zhejiang Hynobius amjiensis National Nature Reserve. Additionally, it is essential to implement management and protection measures specifically targeting seedlings and saplings of P. subaequalis while conducting long-term monitoring of its populations along with their associated primary habitat communities.

Key words: plant community, population structure, Parrotia subaequalis, plant species with extremely small population, Zhejiang Hynobius amjiensis National Nature Reserve