Abstract:

Seed rain is a key link in the natural regeneration of plants.It is of great significance to study the spatial and temporal distribution characteristics of the seed rain of the relict plant Tetraena mongolica for revealing its endangered mechanism and resource protection and utilization.Taking the naturally distributed T.mongolica in the western Ordos area as the research object,the temporal and spatial dynamic characteristics of T.mongolica seed rain and its influencing factors were discussed by continuous observation of the seed scattering characteristics of T.mongolica from 2018 to 2020.The results showed that:1)The seed rain density of T.mongolica was significantly positively correlated with the precipitation in the growing season.The precipitation directly affected the seed setting rate and seed production,and then affected the seed rain density.2)The seed setting rate of T.mongolica was low,but its flower and fruit yield was high,which could ensure the seed production capacity of T.mongolica.The average seed rain density during the observation period was 305 seeds/m².The dispersal period of T.mongolica seed rain lasted from late August to early November,and the peak period of dispersal was in late September.The dispersal curve showed a ‘double peak’ type,which was consistent with the peak period of precipitation.3)The seed rain of T.mongolica was mainly concentrated in the interior and edge of the shrub,accounting for more than 85%,and the seed rain density decreased gradually with the increase of diffusion distance.The seed dispersal distance was 2.7 m at the farthest during the seed dropping period,and the dispersal ability was weak,which limited the expansion of T.mongolica population to new habitats to a certain extent,which may be one of the endangered factors.

Key words: Tetraena mongolica, seed rain, seed dispersal, space-time pattern