Background/Question/Methods The Nutrient Network (NutNet) formed in 2007 as a response to the difficulty of synthesizing ecological information across disparate experimental and observational studies. What began as a small joint effort between US based community ecologists rapidly grew into a global consortium of scientists with unique scientific backgrounds and interests repeating the same nutrient addition and vertebrate fencing experiment across continents. Key to NutNet’s success is an experimental protocol designed to minimize cost and effort while yielding high-quality single-site data that gains power by being replicated across environmental gradients with a centralized, quality assured dataset that is readily available to NutNet participants and collaborators. The core data of NutNet has allowed scientists to answer critical questions about how nutrient supply and vertebrate herbivory shape emergent plant community properties such as diversity and biomass production across global environmental gradients. The NutNet design is also conducive to additional data collection based on site scientist interest and has generated additional data ranging from N mineralization to leaf stoichiometry to grazing intensity. The plethora of data generated has contributed to 97 published papers that have led to a comprehensive understanding of how grassland ecosystems function. Results/Conclusions Foundational NutNet results showed that nutrient co-limitation is both widespread and variable across global gradients. Nutrient co-limitation mediates biomass production and maintains species diversity, contrary to a long-held view that nitrogen is the predominant single limiting resource in temperate grasslands. Additionally, reduced herbivory and increased nutrient supply both lead to decreased light penetration of plant canopies that is a central mechanism of diversity loss. More recent studies on asynchronous responses of species within communities have advanced our understanding of how plant diversity confers resistance to environmental perturbations in grassland ecosystems. These and many more results emerged from the core data collected at all experimental NutNet sites. Add-on studies have been an additional source of insight into these grasslands. For instance, grazing can lead to increased storage of C and N in warmer, eutrophied grassland sites. Studying N mineralization in control plots led to a method of relating potential N mineralization from laboratory studies to realized N mineralization in field system using climatic and edaphic conditions. Ultimately, NutNet has led to a deeper understanding of how nutrients are cycled in grassland systems, from soils to plants to consumers, and the ecosystem ramifications of altered nutrient cycling in a changing global environment.
