Persistent Homology of Pore Structure in a Post-Agricultural Ultisol.

Soil porosity dictates the motion of fluids through soil, and reflects biological and physical factors of soil formation. Using the recent technology of MicroCT scanners, this study begins exploratory annalysis of the three-dimensional structure of soil porosity from the depths of 0-250 centimeters from agregates of Ultisols in South Carolina. These were taken from three land covers: hardwoods, pine forest on regenerating agricultural land and agricultural fields. This study analyses both the pores in an aggregate as well as each pore individually to describe volume, connectivity, shape, and orientation of the pores in a soil. Volumetric measurements from described as a fraction of the total aggregate and compared to measures of bulk density, as well as taken for a volume-size distribution of pores within soil. Shape is annalyzed by examining the circularity of individual pores, using the Crofton perimeter. Connectivity is measured by the distribution of distances to the nearest neighboring pore for each pore and compared to the null Poisson random distribution of pore clustering. Lastly orientation is annalyzed not for the mean but skew of orientations across a sphere. It was found that cultivated fields have consistently fewer small pores than either hardwood or pine stands, though this was not the pattern for large pores. Orientation was consistent for large pores, but smaller pores were essentially randomly distributed.