Objective To explore the distribution characteristics of calcium forms in leaves of Schima superba along an altitude gradient in the Wuyi Mountain and to examine their relationship with environmental factors, thereby providing a theoretical basis for ecological protection and sustainable forest management in subtropical areas.

Method Ten elevation-gradient plots were set up across 800～1 700 m in the Wuyi Mountain Nature Reserve. Mature leaves and corresponding soil samples of S.superba were collected. The contents of six calcium forms, including calcium nitrate/calcium chloride (AIC-Ca), water-soluble calcium (H₂O-Ca), calcium pectinate (NaCl-Ca), calcium phosphate (HAC-Ca), calcium oxalate (HCl-Ca) and calcium silicate (Res-Ca), were determined. Combined with soil physical and chemical indexes (pH, available calcium, etc.), the differentiation rules were revealed by variance analysis, correlation analysis and redundancy analysis (RDA).

Results (1) Leaf Ca forms showed significant altitude differentiation: AIC-Ca reached its highest proportion at 1 201~1 400 m; H₂O-Ca reached its highest proportion at 900 and 1 200 m, coinciding with stronger interspecific competition within this altitude gradient, suggesting a greater requirement for active calcium to adjust to environmental conditions. Res-Ca accounted for a relatively high proportion at 800~1 000 m, indicating a “deposited” Ca pool, that may support antioxidant function and regulate the balance of organic acids in plants. (2) Redundancy analysis showed that altitude was negatively correlated with all calcium forms, soil available calcium was positively correlated with each Ca forms, pH was negatively correlated with AIC-Ca and NaCl-Ca, and positively correlated with other forms.

Conclusion S.superba appears to adapt to changing environments through the synergistic distribution of calcium forms, with patterns primarily driven by altitude and soil available Ca. These findings provide a scientific basis for the study of calcium metabolism regulation mechanism and ecological adaptability of subtropical mountain vegetation.