The effect and impact of current and projected climate change on ecosystem distribution, function, and services is a topic of international concern and wide public interest. In recent years, advances in the effectiveness and availability of field technology have enabled us to start conducting manipulative climate change experiments in the field. Recognizing that soil water is a critical factor affecting the distribution and functioning of vegetation globally, it is not surprising that many global change experiments have focused on soil water dynamics and how they are influenced by warming, elevated levels of CO2, nitrogen additions, and/or altered precipitation dynamics to explain ecosystem responses. In this session, we will review salient findings from several field grassland/old field global change experiments to evaluate the extent to which changes in soil water dynamics provide a common mechanistic link in their respective responses to global warming, primarily, as well as other factors. By considering experiments across a gradient from semi-arid to humid systems, including some experiments with precipitation manipulations, we will also investigate how responses to warming interact with precipitation dynamics to affect critical ecosystem responses, from nutrient cycling to plant species responses. The presenters will present data from five different global warming studies (the Boston Area Climate Experiment; the Oklahoma Global Climate Change Experiment; the Prairie Heating and CO2 Enrichment Experiment; the T-FACE experiment in the Qinahai-Tibet grassland; and the Jasper Ridge Global Change Experiment). The climate change experiments each use infra-red warming treatments, and range in start dates from 1998 to 2008. The talks in the organized session will be arranged from microbial to ecosystem scales to highlight the direct and indirect (water relations) effects of warming on soil nutrient cycling, soil respiration, photosynthesis and NPP, plant productivity and grazing, ecosystem C exchange. The session will culminate in a talk summarizing modeling results for ecosystem carbon and water dynamics for the five study sites represented within this session. In synthesizing results from both experimental manipulations and terrestrial ecosystem modeling, we hope to achieve a mechanistic understanding of the direct and indirect effects of warming, which transcends individual ecosystems/sites and can be applied to broader spatial scales.