Objective This paper explores the effects of different management generations of Robinia pseudoacacia and varied concentrations of rhizosphere soil extracts on the germination of R. pseudoacacia seeds and the growth and development of seedlings in the shallow mountains and hilly areas of western Henan Province of northern China, reveals the allelopathic effects of root exudates on R. pseudoacacia regeneration under multi generation management and cultivation so as to provide a theoretical basis for R. pseudoacacia to overcome continuous planting obstacles and achieve sustainable management.
Method This study selected different generations of R. pseudoacacia forests (first generation, second generation, and third generation forests) as the research object, using bare land as the control, set up three sample plots for basic stand investigation, preparing 1, 5, 10, 50, and 100 mg/mL of R. pseudoacacia rhizosphere soil extracts with different mass concentrations, conducting R. pseudoacacia seed germination and seedling growth experiments, and measuring corresponding indicators such as seed germination and seedling growth.
Result The extract of R. pseudoacacia rhizosphere soil had a certain impact on the germination of R. pseudoacacia seeds. According to the allelopathic comprehensive effect index, in the first generation forest, the inhibitory effect on germination of R. pseudoacacia seeds gradually increased with the increase of concentration of rhizosphere soil extract in different management generations. In the second and third generation forests, only a promoting effect was observed at 5 mg/mL in the second generation forest. The remaining mass concentrations exhibited inhibitory effects. In the third generation forest, as the concentration of rhizosphere soil extract increased, the inhibitory effect on the germination of R. pseudoacacia seeds showed a trend of first weakening and then strengthening. The extract of R. pseudoacacia rhizosphere soil had a certain impact on the growth of seedlings of R. pseudoacacia. According to the comprehensive effect index of allelopathy, in both the first and third generations of forests, the growth of Robinia pseudoacacia seedlings changed from inhibitory effect to promoting effect and then to inhibitory effect with the increase of leaching solution concentration. Both the first and third generations of forests had inhibitory effect at 100 mg/mL, and the inhibitory effect was the strongest. In second-generation forests, different concentrations of Robinia pseudoacacia rhizosphere soil extracts had a promoting effect on the growth of Robinia pseudoacacia seedlings; In bare soil, as the concentration of extract increased, the inhibitory effect on the growth of Robinia pseudoacacia seedlings first increased and then decreased, reaching its maximum value at 50 mg/mL.
Conclusion The root exudates of multiple generations of R. pseudoacacia forests will to some extent inhibit the germination of R. pseudoacacia seeds, but there is no inhibitory effect on the seedling growth stage after seed germination, and it may even be beneficial for its growth.
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