Determining the effects of large-scale shrub removal on soil carbon in the Chihuahuan Desert

Kathleen Schaeffer

Prior to the 19th century, much of the Chihuahuan Desert was made up of perennial desert grasslands, however these grasslands have been greatly reduced by shrub encroachment, which has ultimately led to the shrub dominated landscapes we see today. In the early 2000s, local land managers began implementing large scale shrub removal that has subsequently shifted shrub encroached areas into “novel plant communities” that include: living shrubs, dead shrubs, forbs, grasses, and the interspace between them. Our study set out to determine if this shift in the identity of vegetation classes would alter the content of soil organic carbon, which is a vulnerable yet important resource for the Chihuahuan Desert. Our study area consisted of 15 experimental sites in southwestern New Mexico, with each site including a no-shrub removal area (Control) paired with a shrub removal area (Treatment). In 2017, we sampled soils at all 15 site pairs, at a 5cm depth from the most dominant vegetation/ground cover types present, and we additionally collected vegetation cover data using a line transect method. Soils were analyzed for soil organic carbon using a LECO SC632 Carbon/Sulfur determinator. Our preliminary results show that there is no significant difference in soil organic carbon between the different vegetation/ground cover types at either the Control or Treatment areas. Additionally, there was no significant effect of shrub removal treatment on soil organic carbon. Our findings will help inform land management decisions by providing information on how large-scale shrub removal tactics will affect soil organic carbon in the Chihuahuan Desert region.