Role of natural and anthropogenic disturbance in exotic invasions: Predicting Imperata cylindrica invasion of southeastern forests using ecological niche modeling

Background/Question/Methods

Imperata cylindrica (cogongrass) is at the center of intense concern as a species threatening forests of the southeastern US.  It is a perennial grass native to southeast Asia and has become one of the most serious exotic pests in the southeast occupying over 2 million acres.  We evaluated the effects of both natural and anthropogenic disturbance on the establishment and spread of I. cylindrica.  Specifically, we examined how fire, hurricanes and timber harvesting influenced the spread rates and patterns using ecological niche modeling.  The Blackwater River State forest, a 195,000 acres forest in northwestern Florida that was hit by two major hurricanes (Ivan and Dennis) during 2004-2005, was used as the study area.  

Results/Conclusions

A total of 378 I. cylindrica occurrence points were used for the modeling activity. Niches of cogongrass were modeled in ecological space and niches were projected onto landscapes with potential for invasion.  Results indicated that disturbance events, irrespective of natural or anthropogenic, resulted in significant expansion of I. cylindrica compared to undisturbed areas.  Disturbance events, in general, can exacerbate the invasion of exotic plants like I. cylindrica with serious consequences for the invaded communities.  Identifying vulnerable sites and treating existing infestations before known disturbance events such as harvesting occurs may help combat the issue to a certain extent.