Table 1

ANOVA of cadmium content and pH value in soil"

Fig.1

Effects of biochar treatment on soil cadmium content and soil pH CK represents the control (the seedling substrate contains neither cadmium nor biochar), T0, T2.5, T5, and T10 respectively represent the application of biochar ratios of 0%, 2.5%, 5%, and 10% to cadmium-contaminated soil. Lowercase letters indicate significant differences (P<0.05) among different treatments of the same tree species."

Table 2

ANOVA of the height，ground diameter and biomass changes of Quercus variabilis and Fraxinus chinensis seedlings"

Fig.2

Effects of biochar treatment on seedling height， ground diameter， and biomass of Quercus variabilis and Fraxinus chinensis CK represents the control (the seedling substrate contains neither cadmium nor biochar), T0, T2.5, T5, and T10 respectively represent the application of biochar ratios of 0%, 2.5%, 5%, and 10% to cadmium-contaminated soil. In fig.2C， the upper part of the horizontal axis at 0 represents the aboveground biomass of the seedlings, and the lower part represents the biomass of the underground part of the seedlings. Different lowercase letters in Fig.2A, Fig.2B and the aboveground biomass of Fig.2C indicate significant differences (P<0.05) among different treatments of the same tree species. Difference lowercase letters in the underground biomass of Fig.2C indicate significant differences (P<0.05) based on the interaction effect of treatment and tree species."

Fig.3

Effects of biochar treatments on cadmium content in Quercus variabilis and Fraxinus chinensis seedlings CK represents the control (the seedling substrate contains neither cadmium nor biochar), T0, T2.5, T5, and T10 respectively represent the application of biochar ratios of 0%, 2.5%， 5%, and 10% to cadmium-contaminated soil. The upper horizontal axis at 0 represents the aboveground cadmium content of the seedlings, and the lower part represents the cadmium content in the underground part of the seedlings. Different lowercase letters indicate that the cadmium content in the aboveground and underground parts of the seedlings is significantly different (P<0.05) based on the interaction effect of treatment and tree species."

Table 3

ANOVA of cadmium content and migration indicators in seedlings"

Fig.4

Effects of biochar treatments on the bioaccumulation factor and translocation factor of cadmium in Quercus variabilis and Fraxinus chinensis"

Table 4

ANOVA of the photosynthetic indexes of Quercus variabilis and Fraxinus chinensis seedlings in cadmium-contaminated soil after the application of biochar"

Fig.5

Effects of biochar on photosynthetic indexes of leaves of Quercus variabilis and Fraxinus chinensis CK represents the control (the seedling substrate contains neither cadmium nor biochar)，T0, T2.5, T5, and T10 respectively represent the application of biochar ratios of 0%, 2.5%, 5%, and 10% to cadmium-contaminated soil. Different lowercase letters in Fig.5A and Fig.5B indicate significant differences (P<0.05) among tree species；Different lowercase letters in Fig.5D and Fig.5E indicate significant differences (P<0.05) among treatments; Different lowercase letters in Fig.5C and Fig. 5F indicate significant differences (P<0.05) based on the interaction effect between treatment and tree species."

Table 5

ANOVA of antioxidant enzyme activities in leaves of Quercus variabilis and Fraxinus chinensis seedlings in cadmium-contaminated soil in response to biochar application"

Fig.6

Effects of biochar treatments on activities of three antioxidant enzymes in leaves of Quercus variabilis and Fraxinus chinensis CK represents the control (the seedling substrate contains neither cadmium nor biochar), T0, T2.5, T5, and T10 respectively represent the application of biochar ratios of 0%, 2.5%, 5%, and 10% to cadmium-contaminated soil. Different lowercase letters indicate significant differences (P<0.05) among tree species."