Long-term effects of rootplowing on shrubland succession in Southern Texas

Abstract

Rootplowing has been widely used to reverse the natural conversion of south Texas grasslands to woodlands. This study documented the long-term dynamics of huisache (Acacia smallii Isley), honey mesquite (Prosopis glandulosa Torr.), and other shrubs after rootplowing. Density and canopy cover were estimated for huisache, honey mesquite, and other shrub or tree species at 11 root-plowed sites ranging from 13 to 36 years old and two undisturbed sites on the King Ranch, Jim Wells and Kleberg counties, Texas. On claypan prairie sites, huisache initially dominated and had almost disappeared by 36 years after rootplowing. Huisache did not occur in the undisturbed site. Honey mesquite reestablished more slowly than huisache, but remained relatively dominant in the older sites. Other shrubs did not grow much until huisache began to decrease. At 36 years, density and canopy cover of other shrubs were greater than either huisache or honey mesquite. Trends on sandy loam range sites were similar to respective trends on claypan prairie sites but lagged 15 to 20 years behind. Rootplowing enables huisache to invade and temporarily dominate a site. In the absence of repeated rootplowing huisache declined and eventually disappeared as it was replaced by honey mesquite and other shrub species. Succession from a grassland to a woodland appears to occur more rapidly after rootplowing than in the absence of rootplowing.