Secondary invasion following the reduction of Coronilla varia (Crownvetch) in sand prairie

I investigated the effect of Coronilla varia invasion and subsequent reduction on the plant community and soil nitrogen availability in a degraded Illinois sand prairie. The presence of C. varia significantly increased soil nitrogen availability and significantly decreased native species richness and cover, but neither helped nor hindered a common non-native grass, Poa pratensis. One year after the drastic reduction of C. varia, soil nitrogen remained somewhat elevated and native species richness and cover low, but P. pratensis cover increased nearly six-fold. These results suggest that C. varia's impact might be continued through altered soil nitrogen. More important, however, was the strong response of P. pratensis, which could hinder restoration efforts by competing with native species.