SHRUB SPECIES RICHNESS BENEATH HONEY MESQUITE ON ROOT-PLOWED RANGELAND

Root-plowed rangeland in southern Texas is often dominated by fabaceou s shrubs, We tested the hypothesis that the shrub community present 40 years after rootplowing does not exhibit successional trends toward t he mixed-brush species community that existed before rootplowing, Twen ty shrub clusters, each organized around a central honey mesquite indi vidual, were selected within a control site and a root-plowed (35-40 y ears ago) site at each of 3 locations, Number of all woody plants spec ies including cacti Opuntia spp, and Yucca spp, beneath the nuclear ho ney mesquite was determined, Shrub species richness within clusters in creased with increasing central honey mesquite basal diameter on contr ol and root-plowed sites, Species richness/honey mesquite in root-plow ed (2 + 0.5 species, +/- SE) sites was lower than species richness/hon ey mesquite >200 mm in diameter on control sites (7 +/- 0.4 species/ho ney mesquite). Honey mesquite seedlings (1-60 mm basal stem diameter) composed 39 +/- 14% of the shrubs beneath honey mesquite canopies on r oot-plowed sites compared to less than or equal to 3% of the woody pla nts present on untreated sites, Honey mesquite may continue to dominat e root-plowed sites for some time, since honey mesquite was the major subordinate shrub species on root-plowed sites.