Variation in stem mineral elements among Cunninghamia lanceolata provenances and its impact on growth and carbon sequestration

To clarify the patterns of provenance variation in mineral elements in the stems of Cunninghamia lanceolata, analyze their driving effects on growth and carbon sequestration function, and to provide a theoretical basis for breeding high-carbon-sink germplasm and implementing precise nutrient management.

In 2017, a provenance trial plantation of 36-year-old C. lanceolata at Dagang mountain, Jiangxi Province, was studied. Fifteen geographical provenances were selected to determine the contents of ten elements in stem wood, including carbon (C), nitrogen (N), phosphorus (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), and zinc (Zn), and the stoichiometric ratios of C, N, and P were calculated. By integrating geographic and climatic factors from the provenance origins, as well as growth and carbon sequestration traits, analysis of variance (ANOVA), redundancy analysis (RDA), and structural equation modeling (SEM) were employed to elucidate the associations and driving pathways among these variables.

Obvious provenance variations were observed in stem growth, biomass, carbon storage, and mineral element content. Carbon storage showed the highest variation (the coefficient of variation is 50.73%), indicating substantial differences in carbon sink potential among provenances. Stem P and K contents were the core drivers of increases in DBH, volume, biomass, and carbon storage (For example, the direct path coefficient from biomass to carbon storage was 0.916, indicating an extremely strong positive effect).), while Mn content significantly inhibited biomass accumulation. Geographic and climatic factors of the provenance origin (July mean temperature, annual mean precipitation) indirectly influence growth and carbon sequestration function primarily by regulating the stoichiometric balance of C, N, and P, rather than through the absolute contents of P and K. Cluster analysis identified four superior provenances, including Shunchang (Fujian) and Zhijiang (Hunan), characterized by high P, high K, and high carbon sink potential.

Phosphorus and potassium are the core nutrient elements driving biomass accumulation and carbon sequestration enhancement. Provenance selection and plantation management should prioritize stem P and K contents and their utilization efficiency.