Functional trait analyses, identifying unifying patterns and trade-offs in morphological and physiological traits of plants, have been a cornerstone of recent advances in plant ecology. This has been aided by recent development of global databases now incorporating trait data for tens of thousands of species. Functional traits help relate species composition to ecosystem processes and vice-versa, making them an important tool for predicting impacts of changing environments on plants and plant-mediated ecosystem processes such as carbon and nutrient cycling. These efforts have largely focused on vascular plants, yet other photosynthetic organisms are just as important to the primary production and biogeochemistry of many terrestrial ecosystems. Cryptogams, bryophytes in particular, possess many unique traits that enable them to capitalize on niches where vascular plants are absent in terrestrial (and some aquatic) ecosystems, where they play important ecological roles. Bryophytes can even form the dominant plant functional type in habitats such as forest understories, dryland biocrusts, and peatlands, making it particularly important to understand functional trait relationships in these regions. This session will highlight recent research on functional traits in cryptogams, focusing primarily on bryophytes. The OOS will bring together a range of research at various scales using a diversity of techniques, from the physiological consequences of the morphology of individual shoots to carbon and nutrient cycling at the ecosystem level. The overall aims of the session are to: (1) Contribute to a holistic understanding of the diversity of bryophyte functional traits and how they can help us understand ecosystem processes; and (2) Leverage the research advances in a diverse group of cryptogam ecologists to advance this important topic in ecology.