Microtopography such as gilgai on vertisols and mima mounds on alfisols are important microhabitats.    From Wordnik.com.  [Texas blackland prairies] Reference

Similar to Ecoregion 32a, the shrink-swell clays contain gilgai microtopography with small knolls and shallow depressions that can influence the composition of plant communities.    From Wordnik.com.  [Ecoregions of Texas (EPA)] Reference