Different land-use systems reveal contrasting controls on carbon dynamics in karst critical zones: Physical limitation versus biological regulation

Soil p CO 2 is an important driver of carbonate dissolution and links terrestrial biological processes with groundwater dissolved inorganic carbon (DIC). However, how land use alters soil p CO 2 variability and its coupling with groundwater DIC remains poorly understood, particularly in karst critical zones. Here, we combined two years of high-frequency monitoring with Random Forest (RF), Convergent Cross Mapping (CCM), and structural equation modeling (SEM) to investigate soil p CO 2 dynamics and soil CO 2 to DIC systems, with higher concentrations in shrubland and grassland than in cropland and bare soil. Environmental controls also varied among systems, which indicated that bare soil was primarily associated with moisture variation, whereas vegetated systems showed more complex temperature and moisture responses that were consistent with an additional contribution from vegetation-associated biological CO 2 production. Reconstructed spring water DIC also differed among systems, with lower concentrations in bare soil and higher values in the vegetated systems. The p CO 2 -DIC association was weakest in bare soil, where DIC variation was more closely related to hydrological pulses and soil moisture constraints, but became stronger in cropland and grassland, suggesting closer coupling between soil CO 2 supply and carbonate weathering related DIC generation. Shrubland showed high soil p CO 2 and a distinct DIC response associated with temperature and hydrochemical conditions. Future climate scenario simulations further indicated that soil p CO 2 responses to warming may also differ among land-use systems and may become nonlinear under stronger warming. Overall, our findings indicate differences related to land use in soil p CO 2 dynamics and reconstructed DIC responses in groundwater within the monitored karst simulation platform, highlighting the sensitivity of coupled water and carbon processes in karst critical zones to surface conditions and climate forcing.