Objective To explore the photosynthetic mechanism for productivity of Schima superba mixed planting.

Method This study took one year and two years old seedlings of three S. superba provenances coming from Jian'ou of Fujian Province, Xinfeng of Jiangxi Province and Longquan of Zhejiang Province, which were mix-planted with Cunninghamia lanceolata, as the subjects. The response and laws of growth traits, photosynthetic physiology and chlorophyll fluorescence characteristics of the seedlings to light circumstances set as 100% (L0), 50% (L1) and 25% (L2) of light transmittance were studied.

Result The results showed that the dry matter quality for one year and two years old S. superba seedlings was apparently different with varied light environments. The seedlings of Longquan provenance were superior than that of Xinfeng provenance, which may be related to the strong ability of searching light. During two development stages, the leaf area and chlorophyll content of the seedlings of Jian'ou provenance significantly increased after shading, while the chlorophyll a/b value, the light saturation point, the dark respiration rate and the minimal fluorescence (Fo) value dramatically decreased, indicating that by increasing the leaf area and the chlorophyll content, the seedlings of Jian'ou provenance changed the chlorophyll composition and photosynthetic physiological characteristics, and enhanced the ability of low light capture and transformation, which also showing higher morphology and physiological plasticity. The total leaf area, chlorophyll content and variable fluorescence/maximal fluorescence (Fv/Fm) index of Jian'ou provenance were significantly higher than those in Longquan provenance and Xinfeng provenance under same condition, but the chlorophyll a/b value, light saturation point, light compensation point and dark respiration rate were significantly lower than that of the latter two provenances, which indicated that S. superba of Jian'ou provenance was more shade tolerance, and could be adapted to a wider range of light. Unlike Longquan provenance and Xinfeng provenances, the root-shoot ratio of 2-year-old seedlings of Jian'ou provenance increased significantly after one year's shading, might mean that long-term shading and mixed planting could also be distributed by high biomass redistribution ability. And, increasing distribution of root biomass could enhance the competition with neighbors and promote the accumulation of biomass of the whole seedling at last. The chlorophyll fluorescence parameters of Fo, Fm, Fv/Fm and Fv/Fo were obviously higher for 2 years seedlings than that of 1 year under different light conditions, While, the differences between light treatments were not significant.

Conclusion The productivity of S. superba mixed with C. lanceolata is related to the plasticity to different light environment, and varies with seedling age changing.