We will explore these questions using a comprehensive set of tools including eddy covariance towers, deep CZ drilling, hydrogeophysical surveys, soil and hydrologic sensors, isotopic analysis, synchrotron, geochemical proxies, and genetic sequencing. These efforts build on, and will contribute to, the rich collection of historical data, knowledge, and models at our four primary field sites: the Jornada LTER, the Reynolds Creek CZO, a USDA-ARS site in Kimberly, ID, and irrigated agricultural sites along the Rio Grande valley in Texas.