Though the detrimental effects of invasive plant species on ecosystems have been well documented, not all non-natives exhibit such effects. Little work has been done to understand the mechanisms underlying how non-native species can become invasive species. Studying the microhabitat in which a non-native seedling emerges provides insight into the environmental conditions necessary for establishment and possible invasion. We investigated the influence of microhabitat on the presence of the non-native natal grass (Melinis repens) in Florida scrub using a combination of microhabitat sampling and field germination approaches. We compared microhabitats and vegetation between sites around focal natal grass individuals and random points in disturbed scrub and roadsides, using undisturbed scrub as a reference site. Biomass data were collected using harvested focal natal grass plants. We also conducted a field germination experiment controlling for rosemary presence and disturbance.
Results/Conclusions
Natal grass presence was highest at greater distances to the nearest shrub and in microsites with higher amounts of litter. Presence was negatively associated with oak and palmetto species, but positively associated with cactus. Species richness positively affected natal grass presence, but other measures of diversity (evenness, Shannon’s Index of Biodiversity, Simpson’s Index of Biodiversity) had no significant effect. In comparisons among disturbed scrub sites and undisturbed reference sites, we found that distance to shrub, litter, vegetation cover, tallest neighbor, richness, and Shannon’s index all differed significantly. Of all the variables tested, only species richness in disturbed scrub had an effect on natal grass biomass. In the field germination study, neither rosemary nor disturbance had a significant effect on natal grass germination. The results of this study show that natal grass establishes in distinct microhabitats, which could constrain the speed and coverage of invasion.
