Exploring the Interactive Effects of Seed and Site Limitation on Recruitment Dynamics in Panicum hallii

Seedling recruitment is a critical life history stage that is likely driven by the interplay of seed and microsite limitation and their interaction with seed traits. Here, we performed a factorial experiment involving seed addition and surface soil disturbance to explore the combined effects of seed and site availability using genotypes characterized by varying seed mass and dormancy traits. Additionally, we included hybrids that exhibited recombined seed trait relationships compared to natural genotypes, allowing us to assess the impact of specific seed traits on establishment across different sites. We detected a significant three-way interaction between seed addition, site conditions, and soil surface disturbance, influencing both seedling and adult recruitment in Panicum hallii, a perennial grass found in coastal mesic (lowland) and inland xeric (upland) habitats. This recruitment pattern suggests that lowland and upland establishment at foreign site is constrained by the interplay of seed and site limitations. Notably, soil surface disturbance facilitated recruitment of the upland genotype while constraining recruitment of the lowland genotype across all sites. Our results highlight the importance of seed size and dormancy as key factors impacting recruitment, suggesting a potential interactive relationship between these traits.