The development of mature juniper woodlands has often been associated with decreases in the herbaceous and shrub components of the community. This study focused on changes in species richness and diversity along a successional gradient at both the community and watershed scale in the Owyhee Mountains in southwestern Idaho. Community species richness was relatively constant across the sere. Community species diversity changed as species became less equitably distributed when juniper dominated the site in the later stages of succession. Landscape-scale species richness is predicted to be greatest when all successional stages are represented in the watershed.