Investigation of Crack Development during Evaporation Experiments Using 3-D Laser Scanning.

Soils with vertic properties form cracks that enlarge and change geometry during drying periods. Our objective was to monitor and quantify vertical shrinkage and the development of cracks by sequentially mapping the microtopography of evaporating surfaces of soil cores. The study areas were three National Ecological Observatory Network soil pits in eastern Kansas. These soils were classified as Pachic Udertic Argiustolls, Pachic Vertic Argiudolls, and Pachic Argiudolls with fine particle-size and smectitic mineralogy classes in the control sections. Triplicate cores (8 cm diameter by 5 cm length) were sampled from each of a total of 20 horizons. The UMS HYPROP system was used to monitor pressure potential at 1.25 and 3.25 cm below the surface of the core along with mass while the soil was allowed to dry by evaporation. During the evaporation period, the evaporating surface of each core was scanned multiple times from two positions using a multistripe laser triangulation technique. The resulting digital elevation models (DEMs) were merged to correct for limitations in the field of view of the scanner. Discontinuities in the DEM mesh of each sample represented surface cracks that resulted from shrinking. Morphometrics representing the geometries of the cracks were measured using image analysis software. Relationships between morphometrics, pressure potentials, and soil horizon data (texture, coefficient of linear extensibility, organic matter) for representative core samples will be presented and discussed.