Substantial contribution of inorganic carbon sources to CO2 emissions in calcareous vineyard soils in Germany

In light of climate change and increasing global temperatures, it is important to equally prioritize the study of inorganic carbon dynamics in calcareous soils within temperate ecosystems, as has been done for arid or semiarid environments. A significant area of vineyards in Germany is established on calcareous soils. However, the potential influence of inorganic carbon on CO₂ emissions in these vineyards has not been sufficiently explored when evaluating the carbon footprint of management practices in relation to carbon storage. Therefore, we aimed to differentiate between organic and inorganic sources of CO₂ emissions from six vineyard soils located in the southwest of Germany that had previously received organic soil amendments (OA). Inorganic carbon content varied between 8 and 55 g kg⁻¹ across different sites, with variations observed in the inorganic-to-organic carbon ratio. Soil samples were incubated under standard laboratory conditions for 48 h, and the source of emitted CO₂ was determined using a two-end-member mixing model. The contribution of inorganic carbon to CO₂ emissions was influenced by the quantity of inorganic carbon, with an increase in contribution with increasing inorganic-to-organic carbon ratio. On average, abiotic sources accounted for 5% to 40% of the emitted CO₂ at the different sites, with one site showing no significant contribution of inorganic carbon. CO₂ production from inorganic carbon was higher in the subsoil compared with the topsoil, likely related to the higher content of inorganic carbon in the subsoil. Notably, there was no discernible influence of OA on carbonate dissolution. This study emphasizes the significance of considering abiotic sources of CO₂ emissions in addition to soil respiration in calcareous soils and highlights the need for further investigation to apply these findings at the field scale.