Effects of exploitation and park boundaries on legume trees in the Sonorandesert

Legume trees have been harvested in the Sonoyta Valley since 1975. We estim ated the effects of this woodcutting along the border between Organ Pipe Ca ctus National Monument (U.S.A.) and Sonora, Mexico. We placed 10 x 100 m tr ansects in ephemeral watercourses and uplands on both sides of the internat ional boundary at different distances from the border. Mesquite and ironwoo d trees exhibited significantly higher damage in the Mexican sites than in the protected uplands in the United States. Damage for all the species sign ificantly decreased 500 m form the border, with the exception of ironwood, for which damage remained high within ephemeral watercourses.