Abstract Title: Soil Inorganic Carbon Response to Short-Term Precipitation Variability: Evidence from a Global Drought Manipulation Experiment

Abstract Submitted to: BIOGEOSCIENCES

Abstract Text:

Pedogenic carbonate (PC) represents a key pool of inorganic carbon sequestered in soil. Soil moisture conditions moderate processes involved in PC formation which suggests that precipitation is a primary control of PC formation. Yet, the effect of short-term annual to decadal-scale precipitation variability on the stability and formation of PC is not well-established. Here, we seek to establish the relationship between precipitation variability and the formation and persistence of PC. We analyzed soil samples from the Drought-Net experimental plots at Kessler Atmospheric and Ecological Field Station (KAEFS) for total carbon (TC) and indirectly measured soil inorganic carbon (SIC) using an elemental analyzer. Established in 2016, the Drought-Net experimental configuration includes rainout shelters, which exclude differing proportions of the actual precipitation (0%, 20%, 40%, 60%, 80%, 100%, and a 50% addition) in an existing temperate prairie ecosystem. Our results indicate SIC concentrations increased by 56% in soils subjected to drought conditions by rainfall exclusion. This finding contradicts previous studies that indicate that SIC residence time is associated with the long-term geologic carbon cycle. Instead, the results demonstrate that SIC is particularly sensitive to short-term variation in precipitation, with arid conditions facilitating SIC storage, and wetter conditions driving PC dissolution, resulting in translocation of dissolved inorganic carbon to groundwater. Our work suggests that SIC may be especially vulnerable as precipitation volume and timing change with anthropogenic climate change.