Fokienia hodginsii seedlings tend to vary significantly in response to differences in the surrounding environment, especially when the nutrient environment is heterogeneous and neighboring plants are in competition. Plant physiological differences occur not only in the root system, but also in the photosynthetic characteristics and fluorescence parameters of the leaves. Therefore, in this experiment, three planting modes (single planting, pure planting of F. hodginsii and mixed planting of F. hodginsii and Cunninghamia lanceolata) were set up to simulate different competition patterns. Three heterogeneous nutrient environments (N, P, K heterogeneous nutrient environment) were planted in this experiment, and the homogeneous environments were used as controls to determine the differences in photosynthetic characteristics, fluorescence parameters and the interaction of different environmental factors on each index in different heterogeneous nutrient and planting environments. The interactions of different environmental factors with various indicators were measured. In addition, all treatment combinations were evaluated and ranked by principal components analysis. The results showed that the net photosynthetic rate (P_n) was on average 28.8% and 22.3% higher under monoculture treatment compared to pure and mixed planting in each nutrient environment. Transpiration rate (T_r) and stomatal conductance (G_s) were the lowest under pure planting mode, and the overall mean of Tr was 27.2% and 5.5% lower than monoculture and mixed planting, respectively, and the overall mean of Gs was 36.5% and 14.7% lower, respectively. Intercellular CO₂ concentration (C_i) was higher under mixed and pure planting mode than monoculture, but their overall increments were not significant. P_n, T_r and G_s values of F. hodginsii in the N and P patches were significantly higher than those in the homogeneous patches, whereas the average values of P_n, T_r and G_s in the K patches were slightly higher than those in the homogeneous patches. The average values of leaf F_o, F_v/F_m and qP in each nutrient patch under single planting were higher than those under pure and mixed planting, but most of the differences were not significant. The actual photochemical efficiency (yield), photosynthetic electron transfer rate (ETR) and F_v/F_m in N and P patches were significantly higher than those in the homogeneous patches, whereas qP and NPQ in N and P patches differed due to different planting patterns. Most fluorescence parameters in the K patches were lower than those in the homogeneous patches. Planting patterns and nutrient heterogeneity showed significant interaction effects on P_n, G_s, Yield, ETR, F_v/F_m and NPQ. The highest scores for photosynthetic characteristics and fluorescence parameters of F. hodginsii single planting were in N and P nutrient patches.

Fokienia hodginsii is characterized by shallow and developed lateral roots with no obvious taproot. It can be used as a pioneer tree species for opening up barren land and as a mixed species for creating plantation forests. During the growth process of F. hodginsii seedlings, they are often exposed to heterogeneous nutrient environments and competition for nutrients, water, and space from neighboring plants, which have significant impacts on the growth of F. hodginsii. These impacts are most directly reflected in the root vitality of F. hodginsii, whose physiological changes embody the plant’s adaptability to different heterogeneous nutrient environments and neighbor competition. Herein, high-quality one-year-old F. hodginsii seedlings were subjected to three planting patterns to simulate different competition patterns. The three planting patterns were also exposed to three heterogeneous nutrient environments and a homogeneous nutrient environment (control) to determine the differences in the F. hodginsii seedling growth and root vitality under different heterogeneous nutrient environments and planting patterns. The F. hodginsii seedling height, ground diameter (root neck diameter), and root biomass under the heterospecific neighbor condition were significantly higher than under the single-plant condition. Across heterogeneous nutrient environments, the average seedling height in the N heterogeneous environments was higher than in the P and K heterogeneous environments. The root biomass in the P heterogeneous environment was slightly higher than in the N heterogeneous environment and significantly higher than in the homogeneous and the K heterogeneous environments. Moreover, the average F. hodginsii seedling root vitality under the heterospecific neighbor was the highest, and the root vitality in the N heterogeneous environment was the highest under each planting pattern. The F. hodginsii root catalase (CAT) and peroxidase (POD) activities under the competition patterns were significantly higher than under the single-plant condition. Additionally, the superoxide dismutase (SOD) activity under single-plant was higher than under the competition patterns. At the same time, the F. hodginsii root malondialdehyde (MDA) content was the highest under the conspecific neighbor. Relative to the homogeneous environment, the root CAT, SOD, and POD activities were increased in the N and P heterogeneous environments. The CAT, SOD, and POD activities were highest in the P heterogeneous environment, while the K heterogeneous environment had the highest average MDA content. From the results of principal component analysis, when F. hodginsii seedlings were in N and P heterogeneous nutrient environments and heterospecific neighbor, their growth, root biomass accumulation, and root activity indexes reached better levels.

Currently, research on the F. hodginsii asexual lineage primarily focuses on the screening of growth traits and the control of single fertilizer applications. The effects of the heterogeneity of soil nutrients on root growth and activity have not been studied in detail. Therefore, we propose forest management measures to improve the foraging ability of forest trees in conjunction with stand productivity. In this experiment, annual containerized seedlings of 10 free-pollinated F. hodginsii lines from a primary asexual seed orchard were used as test subjects, and three heterogeneous nutrient environments of nitrogen (N), phosphorus (P), and potassium (K) were constructed. In contrast, homogeneous nutrient environments were used as the control to carry out potting experiments, to study the growth of F. hodginsii lines and the differences in the activities of root enzymes under the three heterogeneous nutrient environments, and to carry out the comprehensive evaluation using the principal component and cluster analysis method. The results were as follows: (1) The seedling height of F. hodginsii family lines under a homogeneous nutrient environment was significantly higher than that of all heterogeneous nutrient environments; the diameter of the ground was the highest under N heterogeneous nutrient environment and significantly higher than that of all the other nutrient environments; the biomass of the root system was the highest under P heterogeneous nutrient environment, which was significantly higher than that of homogeneous nutrient environment and K heterogeneous nutrient environment. The catalase (CAT) activity of F. hodginsii roots was higher than that of homogeneous nutrients in all heterogeneous nutrient environments but not significant, and the superoxide dismutase (SOD) activity was slightly higher than that of K heterogeneous and homogeneous nutrient environments in N and P heterogeneous nutrient environments. SOD activity was slightly higher than that of K heterogeneous and homogeneous nutrient environments under N, and P. peroxidase (POD) activity in the F. hodginsii root system was the highest under the P heterogeneous nutrient environment, which was significantly higher than that of the other nutrient environments. Unlike the activities of the enzymes, the content of malondialdehyde (MDA) in the roots of F. hodginsii was higher in the heterogeneous environment than in all the other nutrient environments. (2) Under N and P heterogeneous nutrient environments, lines 552 and 590 had higher seedling height, ground diameter, and root enzyme activity, while root biomass was highest in line 544; and under K heterogeneous nutrient environments, line 591 had higher seedling height, ground diameter, and root enzyme activity while root biomass was highest in line 551. In contrast to the patterns of seedling height, accumulation of root biomass and activities of root enzymes, family No. 590 had the highest ground diameter of all the F. hodginsii families under the heterogeneous nutrient environments. Family No. 547 had the highest MDA content. In conclusion, it can be seen that N heterogeneous and homogeneous nutrient environments can significantly increase the seedling height and diameter of F. hodginsii compared with P and K heterogeneous nutrient environments, and N and P heterogeneous nutrient environments can also increase the root biomass, root enzyme activities and significantly reduce the MDA content of F. hodginsii. According to the principal component analysis and cluster analysis, it can be seen that among the 10 F. hodginsii family lines, family lines 590 and 552 have higher evaluation in growth, root biomass accumulation, and enzyme activity.