Experimental Alfalfa Hydrology

The goal of this experiment is to quantify the changing hydrological and geochemical properties of a small-scale basalt-alfalfa system and identify any variation that is caused by phenotypical differences in the alfalfa such as rooting depth and density. We are using a setup of individual columns of unweathered basalt planted with different genotypes of alfalfa in a climate-controlled lab facility in France to investigate these relationships. Over the course of several months, the alfalfa will be grown under constant climatic conditions, with variations in watering schedule to look at the full range of responses in the alfalfa, from saturated to water-limited conditions. The hydrological water balance in particular will be measured using scales and discharge collection to determine the partitioning of water between evapotranspiration, discharge, and storage within the basalt. Once completed, this experiment will inform the decision of which alfalfa genotypes to include on a larger hillslope-scale experiment at the Landscape Evolution Observatory at Biosphere 2. This experiment is also just one component of a larger multi-university collaboration that is looking at the evolution and development of landscapes through time including hydrological, geochemical, and biological components.