Savannas and barrens were major components of the historic North American landscape before it was extensively altered by agricultural and urban development during the past century. Rock outcrop plant communities and serpentine barrens are of interest because they are refugia for endemic species adapted to extreme environmental conditions. Many of these communities have been reduced to less than one per cent of their original area and are imperiled ecosystems. This book provides a coherent, readable summary of the technical information available on savannas, barrens and rock outcrop plant communities. It is organized by region into four parts: eastern south-eastern region, central/midwest region, western/south-western region, and northern region. Written by internationally recognized regional specialists, each chapter includes a description of the climate, geology, soils associated with the community, and information about its historic and current vegetation.