Initial effects of invasions by a forest pine (Pinus elliottii) on savanna groundcover vegetation in its introduced range and at home
Results/Conclusions As a group, invaded savanna sites on both continents exhibited lower species richness and plant density than did uninvaded or restored savanna sites. Nevertheless, differences in species richness between invaded and uninvaded sites were significantly greater in Brazil than in Mississippi (94% difference in cerrado vs. 59% in longleaf pine savanna). Tree density, overhead canopy, and needle depth were significantly higher (and species richness and plant density significantly lower) at invaded sites in Brazil than at an invaded and unrestored savanna site in Mississippi or at a site containing native slash pine maritime forest. By one year after implementation of the treatments, needle addition had resulted in a highly significant reduction in both total groundcover plant density and species richness at three uninvaded cerrado sites (88% and 69%, respectively). Needle removal had weak positive effects on density and diversity at invaded sites in Brazil. Although effects of needle addition and removal remain to be examined in Mississippi (but will be presented at the meetings), initial results suggest that higher growth rates and greater needle deposition by slash pine in Brazil compared to Mississippi are in part responsible for differences in impact.