Long-term effects of roller chopping on antiherbivore defenses in three shrub species

We hypothesized that top growth removal results in long-term increases in antiherbivore defenses of blackbrush acacia (Acacia rigidula), honey mesquite (Prosopis glandulosa), and spiny hackberry (Celtis pallida). In 1998, we determined chemical composition and thorn characteristics of leaves and twigs from plants roller chopped once in 1989, from plants roller chopped in 1989 and 1995, and from untreated plants. Honey mesquite had greater crude and digestible protein than untreated plants, and spiny hackberry had lower acid detergent fiber and acid detergent lignin than untreated plants 3 years after roller chopping in 1989 and 1995. Thorns were longer and denser in blackbrush acacia 9 years after one roller chopping treatment. Thorn densities were greater in all three species after two treatments. Long-term increases in thorn length and density after roller chopping may reduce value of the shrubs as browse for herbivores