Investigation and long-term monitoring of Phragmites australis within Virginia's constructed wetland sites

The use of constructed wetlands to replace natural wetlands is becoming pandemic. An investigation using global positioning system technology to map the vegetated communities of 15 of the largest constructed wetlands in Virginia reveals that 80% are colonized by the invasive species, Phragmites australis Trin., and/or aggressive species, Typha sop. Tidally influenced wetlands that have subtidal perimeter ditches have significantly less (P < 0.05) P. australis in the wetland interior than those without perimeter ditches. Fractured regression analyses show that 6 years after construction, P. australis invasion can be extensive. Linear regression analysis suggests that, if conditions remain favorable for P. australis colonization, constructed wetlands could be overrun in 40 years.