Trichoderma longibrachiatum-based fertilizers promote Phoebe bournei seedling growth by regulating plant physiology,...

Phoebe bournei, a rare and endangered plant species in China, exhibits low seedling survival rates and slow growth. Although Trichoderma longibrachiatum-based organic fertilizer is beneficial, it remains unclear whether it can reduce chemical fertilizer dependence while promoting P. bournei growth. Here, P. bournei seedlings were treated with a combination of T. longibrachiatum-based organic fertilizer and reduced chemical fertilizer (designated as the HF treatment). This study was employed to investigate the synergistic mechanisms underlying growth promotion.

Plant physiology, pedology, and amplicon sequencing were used to evaluate the growth of P. bournei seedlings. The HF treatment optimally promoted P. bournei seedling growth, with a 39.8% increase in seedling height compared to the control. Specifically, the treatment elevated the levels of auxin (IAA), abscisic acid (ABA), and jasmonic acid (JA) by 43.6, 50.2, and 63.1%, respectively, compared to the control. This treatment also enhanced plant nitrogen and phosphorus utilization. An increase in the relative abundances of potentially beneficial fungi (e.g., Trichoderma and Trichocladium) and bacteria (e.g., Gemmatimonas and Streptomyces) was observed under the HF treatment, which also suppressed fungal pathogens such as Fusarium.

This study revealed the synergistic mechanism by which T. longibrachiatum-based organic fertilizer and chemical fertilizer co-promote P. bournei seedling growth. Our findings offer a practical strategy for sustainable forestry to enhance the productivity of this rare and endangered tree species.