Dataset and Code for: [Lithologic controls on root-zone storage capacity and vegetation structure in a climate-synchronous region]

Root-zone storage capacity (SR) regulates plant water availability, but lithologic controls on SR and vegetation structure remain poorly constrained in climate-synchronous regions, where seasonal precipitation and evaporative demand are in phase. We quantify SR, its partitioning between soil (SR,soil) and bedrock (SR,rock) and associated vegetation structure across paired granite and limestone landscapes in the Qinling Mountains, China, under identical climatic forcing. Limestone landscapes exhibit higher SR (330 ± 22 mm) than granite (295 ± 18 mm), with a larger SR,rock component (~52 vs. ~29 mm), as estimated using the mass curve technique. The larger SR on limestone is consistent with its finer-textured soils and more extensively weathered bedrock that increases hydraulically accessible storage. Relative to granite, limestone landscapes exhibit higher fractional vegetation cover (FVC, 0.87 vs. 0.77) and tree density (1,298 vs. 1,029 trees ha⁻¹). At the plot scale, FVC scales with SR,soil across both lithologies (R² = 0.70). At the pixel scale, however, SR explains vegetation variability on limestone (R² ≈ 0.33–0.35) but not on granite (R² ≤ 0.04), which reflects rapid drainage and short water residence times in coarse, steep granitic regolith. In monsoon climates, the primary ecological role of SR,rock may shift from drought survival to growth support by buffering recurrent within-season drydowns, which stabilises root-zone water during active growth. These findings provide lithology-based constraints for parameterising root-accessible subsurface storage and its soil–bedrock partitioning. These constraints can be considered in Earth system models to improve the diagnosis of within-season water limitation across humid monsoon landscapes.