This study examines how two major insect herbivores impact pinyon pine-juniper woodlands. The pinyon needle scale insect defoliates juvenile pines while the stem-boring moth kills shoots of mature trees. The impact of these herbivores is regionally extensive and appears to be positively correlated with environmental stress. Taking advantage of two long-term moth and scale removal experiments (15 and 13 years, respectively) we propose to examine the ecosystem effects of herbivory in experimental plots with three classes of trees, 1) susceptible trees infested with moth or scale insects, 2) susceptible trees from which these herbivores have been removed annually for at lease 13 years and 3) trees that are naturally resistant to moth or scales. By comparing tree/soil systems with and without chronic herbivory, we can better understand how herbivores affect productivity and nutrient cycling in pinyon-juniper woodlands, a major vegetation type of the southwestern United States.
