Short-term influences of C4 versus C3 plant growth on dissolved inorganic carbon in a carbonate-poor soil

Background and aimsSoil inorganic carbon (SIC) and its dissolved fraction are recognised as dynamic components of the terrestrial carbon (C) cycle. While they contribute to CO ₂ sequestration and climate regulation, their short-term responses to plant-driven processes remain poorly understood. This study investigates how growth of a C₃ species ( Silphium perfoliatum L.) and a C₄ species ( Zea mays L.) affects dissolved inorganic and organic C (DIC/DOC) dynamics in a carbonate-poor soil under varying soil moisture conditions.MethodsLeachates taken from a two-week lysimeter experiment were analyses for DIC and DOC concentrations, δ ¹³ C isotope signatures, pH, and the data obtained were complemented with in situ CO ₂ efflux measurements. A simplified two-endmember isotope mixing model was used to estimate the contribution of plant-derived C to the DIC pool.ResultsDIC concentrations exceeded DOC across all treatments. Increased CO₂ efflux and higher pH values indicated enhanced soil respiration. δ¹³C _DIC values ranged from − 7‰ to − 20‰, while δ¹³C _DOC remained nearly uniform at − 29 ± 0.7‰. Isotope modelling suggested that up to 62% of DIC could be derived from C₄ plant sources, despite the short timeframe.ConclusionRoot and rhizomicrobial respiration may measurably influence short-term DIC dynamics in carbonate-poor soils. These findings suggest that DIC fluxes could play a more prominent role in soil C cycling than currently assumed, particularly over short temporal scales.