Root length and biomass in mixtures of broomsedge with loblolly pine or sweetgum

Root length density (RLD) and root biomass density (RBD) of fine roots (<2 mm) were examined in a factorial combination of loblolly pine (Pinus taeda L.) and broomsedge (Andropogon virginicus L.) and a factorial combination o f sweetgum (Liquidambar styraciflua L.) and broomsedge to determine the ext ent to which competition may influence belowground plant response. Broomsed ge and sweetgum seedlings were planted, grown for 1 year, and cut before pl anting of pine seedlings. Sampling occurred 1 year after planting of pine. Broomsedge had a significant negative effect (p < 0.10) on RED and RLD of s weetgum and loblolly pine in the upper 30 and 45 cm of soil, respectively. RLD and RED of broomsedge increased with increasing broomsedge density (p < 0.10) and decreased with addition of either tree species, with sweetgum ha ving a greater effect. Patterns in the effects of competitors on RED and RL D were similar to those noted for aboveground biomass. Specific root length (SRL) of broomsedge was three and five times greater than that of sweetgum or loblolly pine, respectively (p < 0.05). The addition of interspecific c ompetitors reduced the percentage of total RLD of pine and sweetgum and RED of broomsedge in the 0- to 15-cm soil depth with a corresponding increase in the 15- to 30-cm depth.