RESUMO
Helianthemum songaricum is a second-class protected plant in China, threatened by decreased population size and fragmentation of distribution area. It is a new record species in Ningxia. We analyzed population structure, spatial distribution, and relationship of different age classes of H. songaricum living in sandy and gravel habitats. The results showed that majority of H. songaricum individuals were belonged to age-class â ¢. The age structure of the population was inverted triangle. The population was at a declining stage. The spatial pattern and spatial association between different age class of H. songaricum were greatly affected by habitat condition, with strong dependence on spatial scale. Compared with sandy habitat, H. songaricum population in gravel habitat tended to be clustered distribution, with a more obvious positive correlation among different age classes. The difference between two habitats was related to environmental condition and plant community structure. H. songaricum from age-class â and â ¡ had mutually dependent ecological relationships.