Above-ground biomass yields at different densities of honey mesquite.

Abstract

Dense stands of honey mesquite (Prosopis glandulosa Torr. var. glandulosa) negatively impact livestock handling and herbaceus forage production; however, very little information is available on the effect of stand density on biomass production of herbage and wood. Our study compared above-ground yields of herbage and wood in undisturbed, cleared, and 3 levels of thinned (100, 300, and 900 stems ha-1) stands of mesquite. Total removal of the mesquite canopy resulted in a 45% increase in herbaceous standing crop compared to the control in the first 2 years post-clearing. Herbage yields for the thinning treatments were intermediate 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). Total 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 (>7,500 stems ha-1). Growth rates of individual mesquite stems were 2- to 3-fold greater (p<0.1) for the l00 and 300 stem ha-1 stands than for the higher- density stands during the relatively wet growing season of 1992. Under the drier 1993 conditions, however, growth rates were similar (P>0.1) for all treatments. Results indicated that severe thinning to less than 900 stems ha-1 increased the amount of available forage and positively influenced the potential growth rates of the remaining mesquite stems.