Over the past two decades, ecologists have recognized the importance of organismal traits in structuring communities and regulating ecosystem functioning. Identifying the relationships among traits provides a means of linking potential biodiversity loss and environmental responses with effects on ecosystem processes. This conceptual framework has been advanced in plant community ecology and more recently adopted in microbial ecology. The goal of this session is to integrate trait-based knowledge across plants and microbes in order to improve predictions of ecosystem processes in a changing environment. One group of speakers will discuss recent progress in the analysis of plant trait data and implications for ecosystem processes. An analogous set of talks will cover recent advances in the analysis of bacterial and fungal traits. Speakers will explore similarities, differences, and integration of trait concepts across plant and microbial systems. A third set of presenters will discuss the incorporation of trait-based theory and data into ecosystem models. Together, these talks will foster a synergistic exchange of hypotheses, approaches, and theory across plant and microbial systems. The session will also open a pathway for knowledge transfer between empiricists who aim to scale up their findings and modelers who can use trait data to make better predictions. Such a transfer should improve ecologists’ ability to answer pressing societal questions about environmental change impacts on ecosystem processes.