Colonization strategies by Lachnanthes caroliana in Feral Swine Disturbed Soils

Background/Question/Methods

Soil disturbance is a natural part of ecosystems and can be the result of abiotic events such as fire, lightning and rain, or biotic means such as rooting or burrowing activities of animals. Soil disturbance can have a positive or negative effect on plant species richness by changing soil properties, and opening up new areas for colonization. Feral swine (Sus scrofa), native to Eurasia and North Africa, can alter the vegetation of an area through extensive rooting. Soil disturbance caused by swine has been shown to increase both native and exotic plant species richness, however observations of rooting in Florida wet prairie have shown that swine rooting can lead to a monotypic stand of the native plant , Carolina redroot (Lachnanthes caroliana). In this study we assessed the primary mechanism of colonization by which L. caroliana dominates soils disturbed by feral swine. We hypothesized that L. caroliana can potentially spread by its prolific seed production, through sprouting of rhizomes and stolons, or by both pathways.

We conducted two studies in the fall of 2012 to determine the re-sproutability of redroot rhizomes, as well as redroot seed presence in the seed bank of a redroot dominated area.

Results/Conclusions

Seedbank results showed that there was significantly more redroot in the above ground species composition than was present in the seedbank. Only one redroot seedling sprouted from collected soil. Our rhizome study results showed an 81.25% overall survival rate of the rhizomes and that a burial depth of 5 cm had a significant positive effect on rhizome survival, final height, and below ground biomass.  Due to the large re-sprouting rate and the low germination rate of redroot seeds from the seedbank we concluded that the mechanism for colonization by redroot in feral swine disturbed soils is likely through its rhizomes.  Further studies on seed viability should be conducted to examine whether the germination rate of redroot seeds is greater under different conditions than our study suggests.