2012 Annual Report 1a.Objectives (from AD-416): Identify mechanisms controlling interannual variability in biomass production in diverse and simple grasslands. 1b.Approach (from AD-416): Establish experimental treatments manipulating the precipitation seasonality and interannual variability in switchgrass monocultures and in mixed-species prairie, and measure responses in above- and below-ground productivity, nitrogen cycling, plant species composition, and plant ecophysiology. 3.Progress Report: This new cooperative agreement provides funds for the University of Texas to hire a post doctoral research associate to conduct research on interactions between precipitation variability, nitrogen cycling, and ecosystem productivity in diverse and monoculture perennial grass systems in the Long Term Biomass Experiment. A post doc was recruited and hired and is planning research for the 2013 field season.