Differences in Soil Microbial Community Structure and Function in the Rhizosphere of Polygonatum cyrtonema Hua under Cunninghamia lanceolata Plantations

This study investigated seedlings and rhizome-propagated seedlings of Polygonatum cyrtonema at different growth stages under a Chinese fir forest, employing metagenomic sequencing combined with soil physicochemical property analysis to compare structural and functional differences in microbial communities between rhizosphere and non-rhizosphere soils, and to explore their relationships with environmental factors. The results showed that rhizosphere and non-rhizosphere microbial communities of P. cyrtonema were jointly influenced by growth stage, rhizosphere effect, and propagation mode, resulting in significant community differentiation(R²=0.487, P=0.001). The Shannon index ranged from 4.811 to 5.583, with no significant differences among treatments; the highest richness was observed in the non-rhizosphere soils of mature seed-propagated plants(ACE=1868.69, Chao1=1917.66). In terms of community composition, at the mid-growth stage, seedlings propagated from seeds showed significant enrichment of Pseudomonas, Paenibacillus, and Nitrospira. In contrast, rhizome-propagated seedlings were enriched in stress-tolerant taxa, including Streptomyces, Arthrobacter, and Nakamurella, during the middle and late growth stages.. Functionally, the non-rhizosphere soils of mature seed-propagated plants were enriched in carbohydrate metabolism, amino acid metabolism, and energy metabolism(LDA=4.17–5.06);the rhizosphere of mid-stage seed-propagated plants was enriched in membrane transport and amino acid metabolism(LDA=4.18–4.86); and the non-rhizosphere soils of mature tuber-propagated plants were enriched in protein folding/sorting/degradation and cofactors and vitamin metabolism (LDA=4.42–4.88). RDA analysis showed that ammonium nitrogen (NH₄⁺-N) was the primary environmental factor influencing changes in microbial functional modules, explaining 18.6% of the variation, with a significant effect. In conclusion, the rhizosphere microbial communities of P. cyrtonema under Cunninghamia plantations showed pronounced structural differentiation and functional remodeling across propagation modes and growth stages. During the middle and late growth stages, seed-propagated seedlings tended to adopt a nutrient- and nitrogen-transformation-oriented strategy, whereas rhizome-propagated seedlings exhibited stronger stress-adaptation and homeostasis-maintenance characteristics. NH₄⁺-N may be a key driving factor underlying these shifts. The study provides a theoretical basis for rhizosphere microecological regulation,cultivation optimization,and disease prevention and control of P. cyrtonema under Chinese fir plantations.