上海大金山岛植被主要组成种的种群年龄结构和存活特征

Revealing the population age structure of plant species is helpful for understanding vegetation dynamics and processes. This study investigated the frequency of common plant species across Dajinshan Island and the size class distribution of 18 dominant or representative species differing in successional status across 13 standard plots on Dajinshan Island, Shanghai, China. The population age structure, seedling pool size, static life table, and survival curve of these 18 species were analyzed to infer trends in their population development. The results showed that, at the island level, the pioneer species Mallotus japonicas was the most dominant, with a plot frequency of 90.6%. The frequency of mid-successional deciduous species, such as Celtis sinensis, Rosa cymosa, Euonymus maackii, Ligustrum quihoui, Symplocos paniculata, Morus alba, and Zanthoxylum ailanthoides was >35%. For late-successional evergreen broadleaf species, the frequencies were 22.6%, 21.7%, 14.2%, and 11.3% for Eurya japonica, Cinnamomum japonicum, Cyclobalanopsis glauca, and Machilus thunbergii, respectively. Most species had a complete population age structure, a large number of individuals with small classes, and a sufficient seedling pool, characterized by an expanding population type. In contrast, the population age structure was sporadic for Pyrus calleryana and M. thunbergii, and unimodal for Cinnamomum camphora, showing a declining population type with few small-class individuals and seedlings. The static life table and survival curve revealed that mortality rates were high for young individuals of S. paniculata, C. glauca, L. quihoui, Maclura tricuspidata, M. thunbergii, Celtis sinensis, and E. maackii and for old individuals of M. japonicas, E. japonica, and C. japonicum. These results suggest that for the key component species on Dajinshan Island, the population structure was complete for pioneer species but constrained for climax species, and the island ecosystem succession process was slow under disturbances in the early and middle stages of secondary succession. Therefore, strengthening the cultivation of the zonal species should be the focus of future studies.