Germination response of invasive plants to soil burial depth and litter accumulation is species‐specific

Questions Plant invasions are considered among the biggest threats to biodiversity worldwide. In a full‐factorial greenhouse experiment we analysed the effect of soil burial depth and litter cover on the germination of invasive plants. We hypothesised that: (a) burial depth and litter cover affect the germination of the studied species; (b) the effects of burial and litter cover interact with each other, and (c) the effects are species‐specific, but dependent on seed size. Methods We tested the germination and seedling growth of 11 herbaceous invasive species in a full‐factorial experiment using four levels of seed burial depths and litter cover. We analysed the effect of burial, litter cover, and their interactions on germination, seedling length and biomass across species and at the species level. Results Soil burial depth and litter cover had a significant effect on the germination of the studied species, but there were considerable differences between species. We observed a general trend of species with bigger seeds being not or less seriously affected by soil burial and litter cover than smaller‐seeded species. Correlations between seed weight and effect sizes mostly confirmed this general trend, but not in the case of soil burial. Conclusions Our findings confirmed that seed size is a major driver of species’ response to litter cover and to the combined effects of litter cover and soil burial, but there is no general trend regarding the response to soil burial depth. Despite its very small seeds, the germination of Cynodon dactylon was not affected by soil burial. The germination of Ambrosia artemisiifolia was hampered by both soil burial and litter cover despite its relatively large seeds. Thus, specific information on species’ response to burial depth and litter accumulation is crucial when planning management or restoration in areas threatened by plant invasions. Effects of soil burial and litter on the germination of invasive species were tested in a full‐factorial greenhouse experiment. Both had significant effects across species, but there were considerable differences between species. We demonstrated that seed size drives invasives’ response to litter, and to the combined effects of litter and soil, and that the effect of soil burial is species‐specific.