INVESTIGATION AND LONG-TERM MONITORING OF PHRAGMITES-AUSTRALIS WITHINVIRGINIAS CONSTRUCTED WETLAND SITES

The use of constructed wetlands to replace natural wetlands is becomin g pandemic. An investigation using global positioning system technolog y to map the vegetated communities of 15 of the largest constructed we tlands in Virginia reveals that 80% are colonized by the invasive spec ies, 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 th an those without perimeter ditches. Fractured regression analyses show that 6 years after construction, P. australis invasion can be extensi ve. Linear regression analysis suggests that, if conditions remain fav orable for P. australis colonization, constructed wetlands could be ov errun in 40 years.