Reproductive traits of Lachnanthes caroliniana (Lam.) Dandy related to patch formation following feral swine rooting disturbance

Understanding plant reproductive traits is important to discerning underlying mechanisms of patch formation by clonal plants after soil disturbance. Reproductive traits that are likely important to patch formation include regeneration ability of rhizomes, seed production and long-term germination ability, and seed presence in the seedbank. In this study, reproductive traits of the clonal plant Lachnanthes caroliniana (Lam.) Dandy that were dominating patches disturbed by feral swine were assessed. The study assessed the ability of rhizomes to resprout in relation to rhizome size (10 cm to 20 cm or 20 cm to 30 cm) and burial depth (buried or surficial). Field surveys were conducted in monocultures to measure the density of inflorescences and seed production. A seed germination and longevity growth chamber experiment was conducted to test the effect of moist or submersed conditions. Finally, a seed bank assay measured the field germination ability of L. caroliniana. Rhizomes had, on average, 81% survival rate and 100% buried rhizomes; rhizome size did not affect survival. Seed production was high with 126,579 seeds per m², but in the growth chamber germination was low (0.5%) and short-lived, with nearly all germinates occurring by 51 days and one germinant at 129 days. Only one seedling of L. caroliniana germinated from the seed bank of soil collected prior to the current year's seed rain, also supporting a short-lived seed bank, as suggested by the timeline of the seed germination study results. These results suggest that reproductive traits of rhizome resprouting and high production of seeds (approx. 600 germinants per m²) may give this species a competitive advantage to form dense patches following feral swine rooting disturbance. Since feral swine continuously return to patches of L. caroliniana, it is likely that this plant and other disturbance-adapted clonal species could increase at the landscape scale as feral swine populations continue to rapidly expand.