Influences of Wildfires on Organic Carbon, Total Nitrogen, and Other Properties of Desert Soils

Fire is a major process in many ecosystems. Knowledge of fire effects on soils is fundamental to making informed land management decisions to meet objectives such as ecological restoration and promoting C sequestration. We assessed 30, 0 to 5 cm soil properties in interspaces (between shrubs) on 32 wildfires, each paired with their own unburned area and ranging in time since fire (TSF) from 2 to 29 yr, in the Mojave Desert. We analyzed relationships of soil properties to burn status (burned or unburned), TSF, and plant community type (blackbrush, Coleogyne ramosissima Torr., and creosote bush, Larrea tridentata [Sesse & Moc. ex DC.] Coville, representing predominant Mojave Desert communities). Organic C and total N were two key properties significantly related to fire, being 25 and 44% greater in burned than unburned areas. Few soil properties exhibited a burn x TSF interaction, indicating that fire presence/absence alone was important. Coleogyne communities displayed greater overall difference between burned and unburned soils than did Larrea communities. Results suggest that: (i) burned areas had significantly greater soil C and total N than unburned areas across communities on this desert landscape, (ii) burned and unburned soils overall were more different in Coleogyne than in Larrea communities, and (iii) TSF was not strongly related to soil properties.