This grant provides support for the acquisition of new environmental sensing and sampling capabilities to enhance and realize the scientific goals of the Landscape Evolution Observatory (LEO) at Biosphere 2 (B2) in Oracle, AZ. The goals of LEO are to permit controlled study of land surface fluxes of water, energy and carbon at the hillslope scale where key observables are monitored at sub-meter scales across a moderately complex landscape. The observed spatial and temporal variability of fluxes and their relationship and feedbacks to controlled and observed climatic parameters would then be used to inform improved models of land-surface water, energy and carbon cycling processes at larger watershed, continental and even global scales. LEO consists of three replicated 340 m2 convergent experimental watershed mesocosms constructed inside a 5,000 m2 environmentally controlled facility at B2. The LEO mesocosms have as their basic design, three, 30 m length, 12 m width, 1 m depth, sloped (approximately 10 degrees from horizontal) steel tanks that have been filled with a grain size homogenized basaltic tephra as a starting soil. The tanks have as part of their frame design, arrays of distributed load cells that permit precise determination of weight changes across the tanks and located above the surface of the tanks are precipitation simulation systems that are rate controllable and can be varied across the surface of the soil tanks. An aspect of the design is that overland flow and erosion is specifically prevented by subsurface pumping and removal of water as the soil horizon saturates ? LEO is not designed for erosion process studies. The tanks are densely arrayed with sampling ports for drawing pore waters and gases and numerous sensor modalities have already been added including soil moisture content probes, soil temperature sensors, soil water potential sensors, soil water samplers, soil gas samplers, CO2 sensors, surface heat flux plates, electrical resistivity tomography probes, piezometers, and water flow and drainage flowmeters. The initial plan calls for 1-2 years of studies of the experimental landscapes devoid of vascular plants followed by the planting of an array of vascular plant types to allow for study of the co-evolution of the physical, chemical, and biological systems in the mesocosms and their influence on the land-atmosphere exchanges of water, energy and carbon.