Few studies have examined soil organic carbon (SOC) quality in arid, hyperthermic ecosystems and the potential role these ecosystems play in global warming. Study objectives were to quantify the impact of mesquite, creosote and grass on SOC distribution and quality in an arid, hyperthermic ecosystem. A density fractionation using sodium polytungstate was carried out to determine the distribution of SOC across all sites. The distribution of SOC shows greater accumulation of light fraction SOC relative to the occluded and mineral fractions. We employed Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFT) to identify molecular components and structures of SOC. Absorption bands for each fraction show considerable differences across vegetation types. Differential thermal analysis will be used to show differences in thermodynamics of the differing SOC fractions. Our results demonstrated significant variation in SOC quality between vegetation types in a hyperthermic ecosystem with potential feedbacks to SOC storage of atmospheric CO₂.