| 14 Apr 2026
Drought-Driven Flux: Soil Inorganic Carbon Stocks Shift Across Sub-Decadal Scales
Abstract. Pedogenic carbonate (PC) represents a key pool of inorganic carbon sequestered in soil. Soil moisture conditions moderate PC formation, suggesting that precipitation is a primary control. Yet the effect of sub-decadal precipitation change on the stability and formation of PC remains poorly understood. Here, we seek to quantify the effect of short-term field manipulated precipitation regimes on formation and persistence of PC. We analyzed soil samples for total carbon (TC) and indirectly measured soil inorganic carbon (SIC) from the Drought-Net experimental plots at Kessler Atmospheric and Ecological Field Station in Oklahoma, USA (KAEFS). Established in 2016, the Drought-Net experimental configuration includes rainout shelters, which exclude differing proportions of the actual ambient precipitation (0 %, -20 %, -40 %, -60 %, -80 %, -100 %, and water addition: +50 %). Increases in SIC were associated with extreme drought treatments while SIC decreases were associated with rainfall addition (p = 0.031). Our findings contradict the established paradigm that SIC residence time aligns with the long-term geologic carbon cycle. Instead, our results demonstrate that SIC is sensitive to sub-decadal perturbations in precipitation, with arid conditions facilitating PC formation and enhanced SIC storage, and wetter conditions driving PC dissolution, resulting in translocation of dissolved inorganic carbon to groundwater. While the relationship between depth to PC-rich horizons and mean annual precipitation has been well-established, this study is one of the first to highlight the dynamic response of PC to sub-decadal shifts in MAP. Our work suggests that SIC may be especially vulnerable as anthropogenic climate change alters precipitation volume and timing.
I enjoyed reading this well-written and interesting manuscript, which addresses an important and timely question regarding the short-term dynamics of soil inorganic carbon (SIC) under changing precipitation regimes. The study provides valuable evidence that SIC can respond to precipitation changes over sub-decadal timescales, challenging the traditional view of SIC as a relatively stable carbon pool. Overall, I believe the manuscript adds value to the growing literature on SIC dynamics.
I have two major comments and few minor suggestions that may strengthen the manuscript. First, the main finding of the study that SIC increased under drought and decreased with water addition is interesting but consistent with the general understanding that moisture influences carbonate precipitation and dissolution. However, the manuscript mentions dust-derived dolomite as a possible explanation for the SIC increase under drought. If dust deposition directly contributed inorganic carbon to the soil, this could be an important explanation for the observed increase, while the decrease under water addition could potentially reflect carbonate dissolution, leaching, or redistribution. I suggest expanding discussion around this.
Secondly, the study is based on a single sampling time point after approximately five years of precipitation manipulation. Therefore, it is unclear whether the observed differences in SIC represent a temporary response caused by redistribution or dissolution, or a persistent change in the soil inorganic carbon pool. I suggest that this limitation be acknowledged. Similarly, a decrease in SIC within the sampled soil profile does not necessarily demonstrate a net loss of inorganic carbon from the ecosystem, as the carbon may have been redistributed to deeper soil layers below the sampled depth of 30–45 cm.
Minor suggestions include: