Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2006
Publication Date: 3/30/2007
Citation: Hickman, K.R., Derner, J.D. 2007. Blackland tallgrass prairie vegetation dynamics following cessation of herbicide application. Rangeland Ecology and Management 60:186-190. Interpretive Summary: A common management practice on remaining tracts of Texas Blackland Prairie is an annual broadleaf herbicide application that is used to increase the relative contribution of warm-season perennial grasses for hay production by decreasing the relative contribution of annual and perennial forbs. These remaining tracts of Texas Blackland Prairie are receiving considerable conservation interest with respect to preserving biological diversity. Yet, it is unclear as to what effect long-term annual herbicide applications have had on plant diversity, and if these applications are removed, what vegetation dynamics would be expected. Removing herbicide applications after 25 years resulted in a dramatic increase in cover of annual forbs, and this resulted in a compositional change in the plant community from former dominance of warm-season perennial grasses to annual forbs. Conservation efforts, with a primary focus of preserving biological diversity, may need to incorporate restoration management actions to increase populations of perennial forbs, the plant group that was most negatively affected by the annual herbicide applications. These management actions may include seed additions or transplantings of desirable perennial forbs.
Technical Abstract: We studied short-term (1-3 years) response 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 fro 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 the June sample 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.