种子雨是植物自然更新的重要基础,研究孑遗植物四合木种子雨的时空分布特征,有助于揭示其濒危机制,对该物种的资源保护与利用具有重要意义。以西鄂尔多斯地区自然分布的四合木为研究对象,对2018—2020年四合木种子散落特征进行连续观测,分析四合木种子雨的时空动态变化特征及其影响因素。结果表明:1)四合木的开花数、结实量及其种子雨密度均随生长季降水量的增加而增加。2)四合木结籽率较低,但其开花结实量较大,可以保证四合木的种子生产能力,观测期内种子雨密度平均为305粒/m²;四合木种子雨散落期从8月下旬持续到11月中旬,散落高峰期在9月下旬,散落曲线呈“双峰”型,其峰值出现时间与降水量高峰期吻合。3)四合木种子雨主要集中在灌丛内部和边缘区域(占总量的85%以上),种子雨密度随扩散距离的增加呈递减趋势;整个落种期内,种子最远扩散距离仅为2.7 m,扩散能力较弱在一定程度上限制了其种群向新生境的扩张。

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.