To investigate the effects of varying shading intensities on the growth and photosynthetic physiological characteristics of Cyphomandra betacea seedlings, clarify the optimal light intensity range for seedling growth, and to provide theoretical references and technical guidance for understory intercropping and intensive seedling production.

One-year-old Cyphomandra betacea seedlings were selected as experimental materials. Four shading treatments were established: full sunlight (CK, 100% natural radiation, NR), light shading (S₁, 75% NR), moderate shading (S₂, 50% NR), and severe shading (S₃, 30% NR). Growth and physiological indices including seedling height, ground diameter, single-leaf area and photosynthetic pigments content were measured. Correlation analysis and fuzzy membership function comprehensive evaluation were performed to elucidate the light adaptation mechanism of seedlings.

1) Seedling growth was significantly affected by shading treatments (P<0.05). In the S₁ treatment, seedling height increased by 10.5% compared with the CK group and exhibited the best leaf expansion performance, whereas the S₃ treatment significantly inhibited stem radial growth; 2) Photosynthetic measurements demonstrated that the S₁ treatment maintained a relatively high net photosynthetic rate (7.84 μmol·m^-2·s^-1), with a significantly higher non-photochemical quenching (NPQ) value (11 489.98) than the CK group. Moderate shading was proven to enhance the heat dissipation capacity and effectively alleviate leaf photoinhibition; 3) Correlation analysis showed that seedling height had an extremely significant negative correlation with net photosynthetic rate (r=-0.587, P<0.01), while stomatal conductance was extremely significantly positively correlated with net photosynthetic rate (r=0.731, P<0.01); 4) The fuzzy membership function evaluation results verified that the S₁ treatment was the optimal growth condition, with an average comprehensive value of 26 116.65.

Cyphomandra betacea seedlings can adapt to shading stress via morphological plasticity (plant height promotion and leaf area expansion) and photochemical efficiency regulation. In summary, 75% NR is identified as the optimal light condition for seedling growth, which can be applied to understory intercropping and shading-based intensive seedling cultivation.

To investigate the effects of foliar ration fertilization on the growth and nutrient accumulation of Cyphomandra betacea seedlings, and to screen out the optimal foliar fertilization formulations of nitrogen, phosphorus and potassium.

A three-factor (N, P, K) three-level (1%, 2%, 3% concentration level of N fertilizer; 1%, 2%, 3% concentration level of P fertilizer; 1%, 2%, 3% concentration level of K fertilizer) orthogonal experimental design was used with one-year Cyphomandra betacea seedling live seedlings as the experimental material, a total of 10 foliar fertilizer rate combinations including CK were designed to analyze the effects of foliar fertilization with different nitrogen, phosphorus and potassium rates on the growth biomass, C, N, P and K contents and their nutrient accumulations and stoichiometric ratios of Cyphomandra betacea seedlings, LSD multiple comparison analysis, correlation analysis, principal component analysis and fuzzy comprehensive evaluation analysis of affiliation function were also used to screen out the best combination of foliar fertilizer ratios to promote the growth of Cyphomandra betacea seedlings.

Cyphomandra betacea seedling growth biomass, C, N, P and K contents and their nutrient accumulation and stoichiometric ratios differed significantly (P<0.05) among the fertilization treatments. Fertilization facilitates the growth of Cyphomandra betacea seedlings in terms of seedling height and ground diameter, as well as the accumulation of biomass, carbon, nitrogen, phosphorus and potassium nutrients in all organs. The biomass and nutrient accumulation of Cyphomandra betacea seedlings in all fertilization treatments as a whole showed that leaves > stems > roots; under different fertilization treatments, the ω(C)∶ω(N) and ω(C)∶ω(P) of all organs of Cyphomandra betacea were basically lower than that of the control group CK, and the ω(N)∶ω(P) was basically greater than 16, whereas the ω(N)∶ω(K) was much less than 2.1 and the ω(K)∶ω(P) was much greater than 3.4. All the indicators of Cyphomandra betacea seedlings under E5 fertilization treatment were optimal or better, and plant growth was optimal under this fertilization treatment.

Growth of Cyphomandra betacea is limited by the P element, and plant nutrients are preferentially distributed to leaves and stems; all fertilizers were able to promote the growth and nutrient accumulation of Cyphomandra betacea seedlings, and this promotion was optimally carried out under the treatment of E5 (N₂P₂K₃), i.e., ω(N)∶ω(P)∶ω(K)=2%∶2%∶3% was the optimal formulation for foliar spraying of Cyphomandra betacea seedlings. The study may provide some reference to farmers for precise and quick fertilization for Cyphomandra betacea growth.

The purpose of this study was to explore the effects of mixing ratio on growth and competition for Betula alnoides and Castanopsis hystrix, so as to provide evidences for rational mingling and further efficient management of their mixture.

The growths of B. alnoides and C. hystrix were investigated in 6-year-old mix trial plantations in Pingxiang, Guangxi, which included five treatments: monoculture of each species and mixtures of B. alnoides and C. hystrix with ratio as 1∶1, 1∶3 and 1∶5. The intraspecific and interspecific competition index of both species were calculated with Hegyi's competition model, the differences of tree growth and competition among these treatments were compared, and correlation between tree growth and competition was clarified.

Compared with monoculture, the mixing treatments significantly promoted tree height, diameter at breast height (DBH), crown width (CW), basal area at breast height (BA), crown length (CL), crown volume (CV) and crown surface area (CSA) of B. alnoides; and for C. hystrix, DBH, CW, CL, CV and CSA of 1:1 mixing treatment were significantly higher than those of its monoculture. The intraspecies competition index decreased significantly for B. alnoides while increased for C. hystrix with increasing proportion of C. hystrix; the highest interspecific competition index were found in treatments of mixing ratio of 1∶1 for B. alnoides and 1∶3 for C. hystrix. The intraspecific competition indexes were in significantly negative correlation with DBH, tree height, CW, BA, CL, CV, CSA, and were significantly positively correlated with tree height to diameter ratio (H/D) and crown ratio for both species; and the interspecific competition indexes were significantly and negatively correlated with DBH, tree height, height to crown base (HCB), CW, BA, CV, CSA for B. alnoides, while were only in significantly negative correlation with tree height for C. hystrix.

As a whole, mixing ratio of 1∶1 was recommended in the practice for establishing mixture of B. alnoides and C. hystrix in southern China.