Positive plant interactions and community dynamics : an introduction / Francisco I. Pugnaire -- Do positive interactions among plants matter? / Ragan M. Callaway -- Plant interaction indices based on experimental plant performance data / Zaal Kikvidze and Cristina Armas -- Consequences of facilitation on species diversity in terrestrial plant communities / Lohengrin A. Cavieres and Ernesto I. Badano -- Biotic interactions, biodiversity, and community productivity / Richard Michalet and Blaise Touzard -- Arbuscular mycorrhizae and plant-plant interactions : impact of invisible world on visible patterns / Mari Moora and Martin Zobel -- Plant communities, plant-plant interactions, and climate change / Rob Brooker -- Synthetic analysis of the stress-gradient hypothesis / Christopher J. Lortie.