The Department of Energy's Office of Science is seeking applications for research in Environmental System Science (ESS). The goal of the ESS program is to advance an integrated, robust, and scale-aware predictive understanding of terrestrial systems and their interdependent microbial, biogeochemical, ecological, hydrological, and physical processes. This opportunity will consider applications that focus on measurements, experiments, field data, modeling, and synthesis to provide improved understanding and representation of ecosystems and watersheds. The ESS program scope advances foundational process knowledge with an emphasis on understudied ecosystems. • The ESS program will support research in three Science Research Areas: plant-soil-microbe interactions, synthesis studies using existing data, and synthesis studies on contributions and vulnerabilities of Earth system processes in marginal and degraded lands. • The program uses a systems approach to develop an integrative framework to elucidate the complex processes and controls on the structure, function, feedbacks, and dynamics of terrestrial and watershed systems. • Incorporation of scientific findings into process and system models is an important aspect of the ESS strategy. • The estimated funding for this opportunity is $6,000,000, with an award ceiling of $1,000,000 and an award floor of $100,000.