Intraspecific seed interactions alter seedling emergence of Lespedeza cuneata under field conditions

There is growing recognition that seeds influence one another prior to, or shortly after, germination. Both interspecific and intraspecific seed–seed interactions have been reported, but for the latter, the evidence is almost exclusively from laboratory and greenhouse studies so that it is unclear whether such intraspecific seed interactions occur under field conditions. We tested how Lespedeza cuneata seed density influenced seedling emergence within a native grassland located in Kansas, USA and whether this response was related to seed leachate. The percentage of L. cuneata seedlings that emerged under field conditions was negatively related to seed density. After confirming this pattern in the greenhouse, we found that at low seed densities, addition of seed leachate had similar effects on seedling emergence as high seed densities in the absence of leachate. Our results provide some of the best evidence to date, that intraspecific seed density can influence seedling emergence in the field and that these effects are likely linked to seed leachate.