Emergent Climate Change Impacts on the Soil C and N Cycles in the Mojave Desert

The Mojave Desert has warmed >2 degrees C, and aridified, in the past 50 years, making it a strategic location to investigate climate change impacts on arid soil processes. We resampled a climosequence of soils in the Mojave first sampled in 1973 and compared current soil properties to those 45+ years earlier. Radiocarbon changes revealed that C is cycling rapidly through the soils, particularly near the surface, with a temperature-sensitive decomposition rate (Arrhenius E-a = 66 kJ/mol). Significant decreases in soil C/N ratios and increases in delta N-15 values occurred, suggestive of enhanced rates of soil C and N cycling and their losses. Covariation between changes in soil radiocarbon, delta C-13, delta N-15, and C/N point toward emerging chemical impacts on the coupled C and N cycles in response to climate change.