Blackland Tallgrass Prairie Vegetation Dynamics Following Cessation of Herbicide Application

We studied short-term (1–3 years) responses of plant species and functional group abundances, richness, evenness, diversity, and similarity following cessation of 25 years (1972–1997) of herbicide application in a remnant of Blackland Tallgrass Prairie in central Texas. Substantial increases in plant cover from 1998 to 2000 were observed for annual forbs (359%–900%), primarily attributable to firewheel (Gaillardia pulchella Foug), but C4 perennial grass cover only marginally increased (22%–23%). These disproportionate increases elicited a directional compositional change in the plant community with dominance shifting from C4 perennial grasses to annual forbs. Species richness, evenness, and diversity decreased from 1998 to 2000 for May, but increased for June, sampling date. Conservation efforts pertaining to remnants of Blackland Tallgrass Prairie need to be cognizant that dramatic short-term effects on vegetation dynamics will occur following cessation of annual herbicide applications, and that enhancement of perennial forbs may require seeding or transplanting species.