ABOVEGROUND BIOMASS YIELDS AT DIFFERENT DENSITIES OR HONEY MESQUITE

Dense stands of honey mesquite (Prosopis glandulosa Torr. var, glandul osa) negatively impact livestock handling and herbaceous forage produc tion; however, very little information is available on the effect of s tand density on biomass production of herbage and wood. Our study comp ared above-ground yields of herbage and wood in undisturbed, cleared a nd 3 levels of thinned (100, 300, and 900 stems ha(-1)) stands of mesq uite, Total removal of the mesquite canopy resulted in a 45% increase in herbaceous standing crop compared to the control in the first 2 yea rs post-clearing, Herbage yields for the thinning treatments were inte rmediate although herbage yields for the 900 stems ha(-1) (2,017 kg ha (-1)) treatment was similar (P > 0,1) to the control (1,849 kg ha(-1)) and lower (P < 0.1) than the cleared treatment (2,684 kg ha(-1)), Tot al wood production was significantly (P < 0.1) lower for the 3 thinned treatments (481 to 1,214 kg ha(-1) yr(-1)) than the control (8,128 kg ha(-1) yr(-1)) because of the higher stem density for the control (> 7500 stems ha(-1)), Growth rates of individual mesquite stems were 2- to 3-fold greater (P < 0,1) for the 100 and 300 stem ha(-1) stands tha n for the higher-density stands during the relatively wet growing seas on of 1992, Under the drier 1993 conditions, however, growth rates wer e similar (P > 0.1) for all treatments. Results indicated that severe thinning to less than 900 stems ha(-1) increased the amount of availab le forage and positively influenced the potential growth rates of the remaining mesquite stems.