Patterns and determinants of calcium concentrations in forest litter and different soil horizons in warm-temperate China

[Display omitted] •Calcium accumulates in forest litter under broadleaved forests instead of coniferous forests.•Basal area and soil C/N dominantly regulated the litter and soil calcium, respectively.•The links between calcium in litter and different soil horizons vary among forest types.•The structural equation model showed strong effects of calcium in deep soil (30–50 cm) on calcium in forest litter. Calcium is an essential nutrition for the integrity and structure of plant cells, and is generally neglected because of its high abundance in temperate forest soil. To date, little is known about the changes in soil Ca and the main natural drivers in the conserved forests. Here, the concentrations of Ca in forest litter and different soil horizons (0–10, 10–20, 20–30, and 30–50 cm) from 234 forest plots were measured. Spatial variations in litter and soil Ca concentrations beneath different forest types were determined, and a structural equation model (SEM) was constructed to evaluate the causal pathways of the biotic and abiotic drivers. The results showed that litter Ca concentration beneath broadleaved forests and mixed broadleaf-conifer forests (22.62 and 19.76 mg/g, respectively) were significantly greater than that beneath the coniferous forest (15.35 mg/g). The Ca concentrations in the soil significantly increased with latitude (soil depth 20 cm) on litter Ca concentration. The basal area and soil C/N had negative and positive direct effects on Ca concentration in topsoil (soil depth