This data package contains data on soil nitrogen mineralization potential in a variety of grass and mesquite habitats during the early years of the Jornada Basin LTER project (I-II). Soil cores were collected from Jornada Experimental Range and Chihuahuan Desert Rangeland Research Center (CDRRC) lands in May 1986, and observed in a leaching incubation study. The purpose of this study was to measure inorganic soil nitrogen in the context of the shift from grasslands to mesquite dominated ecosystems. Sites include fluff grass (Dasyochloa pulchella), black grama (Bouteloua eriopoda), Sporobolus/Gutierrezia, playa mesquite (Prosopsis glandulosa), and arroyo mesquite ecosystem types. Soil samples were collected on May 12-13, 1986 within the clumps of grass or beneath mesquite at each site, generally 20 cm deep or to the hard pan (whichever came first). During the incubation study, inorganic nitrogen leaching was measured for 28 weeks for each sample. This study is complete.