Population Structure and Dynamic Analysis of the Rare and Endangered Plant Camellia longistyla

Camellia longistyla Chang ex F.A. Zeng et H. Zhou is a rare, endangered and endemic economic plant in Guizhou Province, China. This species is distributed narrowly from 950 to 1400 m elevation in mixed evergreen and broad-leaf deciduous forests in the Jinshagou Alsophila spinulosa Natural Reserve and Leigongshan Natural Reserve. We surveyed naturally-occurring C. longistyla by establishing sampling plots in two typical densely-covered areas (Wangxiangpo A and Fangshan B). Time-specific life tables and survival function curves were established and drawn based on diameter class. We analyzed the survival curve (ln(l_n)) and survival function curve (S_n), and predicted population development trends by population quantity dynamics (V_n, V_pi) and time-sequence models. Results showed that: On the whole, the age structure of the C. longistyla population was declining type in the early stages, indicating more middle-aged trees and fewer young individuals. The survival curve was Deevey-Ⅰ type. Time-specific life table analysis and correlation curves revealed that the population structure of C. longistyla exhibited a slump in the early stage, stability in the middle stage and gradual decline in the late stage. According to the population dynamic analysis results, seedling supplementation was insufficient in both populations and natural regeneration was difficult, although there was a certain recovery potential. Furthermore, population A was sensitive to changes in the environment. Time-sequence analysis indicated that the decline in the two populations began in the last 1-2 age-class time. If effective protective measures are not taken, after four age-classes, the native populations will become typical declining type. With systematic study on population characteristics and propagation, together with strengthened in-situ conservation, artificially-cultivated seedlings can be returned to original habitat or introduced to similar habitat so as to increase population and dispersal ability. Such measures will be of great significance for the effective protection, development and utilization of C. longistyla germplasm resources.