Landscape Evolution Observatory (LEO)
A major outgrowth from SAHRA's research on the ecohydrologic impacts of vegetation change is the design and construction of artificial hillslopes in the Landscape Evolution Observatory (LEO) within the Biosphere 2 research complex.
SAHRA researchers partnered with the B2 Institute to develop a massive interdisciplinary experiment to study how climate and vegetation affect the surface and subsurface structure of this critical zone. In this 10-year project, we are constructing large experimental landscape units (hillslopes) that will be used initially to study the interactions of geochemical changes and water flow, and later to elucidate the effect of plant colonization in hydrological and biogeochemical change.
The Biosphere 2 Landscape Evolution Observatory (LEO) consists of three replicate physical models of the areas of mountain landscapes that sit above river channels - "hillslopes". At 360 m2, the artificial watersheds of LEO approach the physical scale and mimic the form of natural, convergent, zero-order drainage basins. But, they are far more densely instrumented and subject to a higher level of control than is possible in natural systems. The 0.2 ha part of Biosphere 2 that has been renovated for this project has the capability to be cooled and heated over a range of ~40 C. The facility lends itself to careful mass-balancing of atmospheric fluxes, and control of atmospheric composition of vapor and gas. The landscapes are subject to nine precipitation intensities from 0.5 to 4.5 cm/hr.
Measurement capability in LEO includes measurement of soil water content, soil temperature, and soil water potential at ~450 locations on each of three hillslopes, soil heat flux at 24 locations, soil CO2 concentration at 50 locations, soil water hydraulic head at 34 locations, and three-dimensional moisture field imaging using electrical resistivity tomography. Soil water and gas are sampled from hundreds of soil locations. Precipitation, surface water and subsurface water fluxes are measured, as is surface sediment flux. The total weight of each landscape is tracked in real time using custom load cells, enabling LEO landscapes to function as the world's largest weighing lysimeters at a sensitivity approaching the equivalent of 0.001 m of precipitation. Fine-scale topographic changes are monitored using a 3D laser scanner system. Atmospheric characteristics are measured using weather stations, net radiometers, and real time gas analyzers. Researchers can access any point on the landscapes without disturbing the surface using custom traveling gantries.
For more information, please visit: http://leo.b2science.org/.