Population structure and number dynamic characteristics of endangered plant Ormosia hosiei in Sichuan and Guizhou provinces, China

Abstract

Ormosia hosiei is a rare and endangered plant that is narrowly distributed in South China, with important economic and humanistic values. In order to find out its survival status and the reasons that restrict its development, we investigated the natural populations of O. hosiei in four regions of Guizhou and Sichuan provinces. According to the distributive characteristics of different populations, we set up two 20 m × 20 m for each population by using the method of plot investigation and conducted a community survey in each plot. The structural characteristics of O. hosiei populations were analyzed by establishing population static life tables and drawing populations survival curves. Four survival functions, number dynamic index, and time series model analysis were used to describe survival status. The results were as follows: (1) The age-class structure of O. hosiei populations were in the shape of “J”at Hezhu Village and Ganerpan Village, in the shape of “Dumbbell”at Chenjiawan Village and Rongchun Village, the populations had strong natural renewal ability, but middle-aged individuals were easily missing. (2) The four populations belonged to the increasing type, the survival curves of populations are close to Type Deevey-Ⅱ, the disappearance rate and mortality rate of O. hosiei populations showed a “Multimodal” pattern in Hezhu Village, Chenjiawan Village and Rongchun Village, indicating that the populations were susceptible to external disturbances in the middle period. (3) All O. hosiei populations in different regions appeared to decrease in the early stage and keep dynamically stable in the medium-late stage, and the formation reasons were related to the topographic characteristics of mountainous areas and the seed dispersal characteristics of O. hosiei. (4) RDA analysis showed that altitude and slope were the dominant factors affecting the populations structure of young individuals, and interference intensity was the main factor affecting the number structure of older individuals. All the above results indicate that the structural and number characteristics of O. hosiei populations in different regions are restricted by the topographic characteristics of mountainous areas, the reproductive characteristics of O. hosiei and the environmental pressure; By controlling the density of young individuals and managing the growth space of middle-aged individuals, we can increase the survival rate of the seedlings, promote the healthy growth of middle-aged individuals, and maintain the stability of the natural populations of O. hosiei.

Keywords

• ormosia hosiei
• endangered plant
• population structure
• static life table
• survival function