Differences in Soil Carbon, Nitrogen, Phosphorus, and Potassium Stoichiometry among Styrax zhejiangensis and Eight Coexisting Plant Species

Styrax zhejiangensis is a protected plant species with an extremely small population endemic to Zhejiang Province. Studying the carbon（C）, nitrogen（N）, phosphorus（P）, and potassium（K）contents and their stoichiometric ratios in the root-zone soils of S. zhejiangensis and its associated plants can provide a scientific basis for soil management in the conservation of this species. Soil samples from the 0–20 cm layer around the roots of S. zhejiangensis, synergistic plants（Lithocarpus glaber, Camellia fraterna, Machilus thunbergii, Symplocos sumuntia）, and competitive plants（Cinnamomum subavenium, Elaeocarpus decipiens, Ternstroemia gymnanthera, Eurya hebeclados）were collected from nine standard plant individuals. The contents of C, N, P, and K were measured, and their stoichiometric ratios were calculated. The results showed that:（1）The soil P contents in the root zones of S. zhejiangensis and synergistic plants were 1.28 g·kg⁻¹ and 1.22 g·kg⁻¹, respectively, significantly higher than that of competitive plants（0.85 g·kg⁻¹）（P＜0.05）. In contrast, no significant differences were observed in soil C, N, and K contents among the three plant types.（2）The soil C/P, N/P, and K/P ratios of competitive plants were 32.23, 1.41, and 10.56, respectively, significantly higher than those of S. zhejiangensis and synergistic plants（P＜0.05）. No significant differences were found in soil C/N, C/K, or N/K ratios among the three plant types.（3）Soil C and N showed a highly significant positive correlation（P＜0.01）, whereas C, N, and P, as well as C/P and N/P, exhibited highly significant negative correlations（P＜0.01）. In conclusion, synergistic plants may alleviate P limitation for S. zhejiangensis during growth by maintaining higher soil P content, while competitive plants tend to compete for limited soil P resources. For the conservation of this species, it is recommended to apply phosphorus fertilizer appropriately, thin out competitive plants moderately, and replant synergistic plants to improve its habitat conditions.