Effects of herbivory on twig dynamics of a Sonoran Desert shrub Simmondsia chinensis (Link) Schn.

Density of jojoba was similar but plant size and cover were greater inside than outside a 48-yr-old livestock exclosure in C Arizona. Twig growth was greatest in spring while greatest herbivory occurred in late spring and summer after senescence of annual herbaceous plants. Grazed shrubs had greater twig growth than ungrazed shrubs resulting in similar net increases in twig length and biomass. The ability of jojoba to regrow from lower lateral or apical buds after removal of outer twig ends allows it to tolerate herbivory in the ecological context of the study site. Grazed shrubs had lower male and female flower densities than ungrazed shrubs. Periodic spring rest or control of stocking to limit grazing intensity is recommended to maintain shrub size and total production. -from Authors