作为山地森林生态系统附生植物区系的重要组分,兼性附生植物是一类既能附生于树皮,又能根植于土壤的特殊植物类群,是同一物种在不同生长基质上的生态型。研究兼性附生植物在不同生境下的化学计量特征及其变化,有助于了解兼性附生植物对生境变化的响应与养分利用策略。以云南哀牢山亚热带山地湿性常绿阔叶林中常见的兼性附生植物长叶粗筒苣苔(Briggsia longifolia)为研究对象,通过对其地生、树干基部和1.3 m树高处不同生境的基质、植株叶片和根系中C、N、P含量及其化学计量比的测试与分析,探讨不同生境下兼性附生植物的化学计量特征及其养分利用策略。研究结果显示:长叶粗筒苣苔的生长基质以及各器官的化学计量特征在不同生境间存在差异。林地土壤C、N、P含量以及C∶N、C∶P和N∶P均低于树干附生基质,树干基部基质的C、N、P化学计量特征介于两者之间。与地生生境相比,在附生生境下长叶粗筒苣苔的N、P含量较高,而C∶N、C∶P和N∶P则较低,说明其养分利用效率较低。在3种生境下长叶粗筒苣苔叶片的N含量与N∶P均低于根系,而C∶N则高于根系。长叶粗筒苣苔叶片中N、P元素以及N∶P比的内稳性指数高于根系,叶片和根系的内稳性均表现为:HN∶P > HN > HP。根中较弱的化学计量内稳性,说明其通过调节根系的元素组成与养分吸收来维持叶片代谢活动的相对稳定。综上所述,兼性附生植物通过调整其在不同生境间的养分吸收与利用策略以及叶片和根系间的化学计量内稳性,以此来适应生境的变化。这些研究结果丰富了植物生态化学计量学理论,也为深入研究森林生态系统生物多样性形成及其维持机制、以及山地森林资源的保护与管理提供了科学依据。
Facultative epiphytes is an important component of epiphytic flora of montane forest ecosystems, it refers to a special plant that can both grow in epiphytic and terrestrial habitats. Epiphytic and terrestrial individuals of the same species are different ecotypes that present on different substrates. Studying the stoichiometric characteristics of facultative epiphytes in different habitats is helpful to understand the response of facultative epiphytes to habitat shift and nutrient utilization strategies. Briggsia longifolia is a dominant species of facultative epiphytes in montane moist evergreen broad-leaved forest of the Ailao Mountains, Yunnan Province. This species belongs to Gesneriaceae, which not only has important medicinal, horticultural and ornamental values, but also has high value in the research of taxonomy, evolutionary systematics and phytogeography. In this study, C, N, and P concentrations and their stoichiometric ratios in substrates, leaf and root of B. longifolia among different habitats were analyzed. The results showed that there were differences in the stoichiometric characteristics of the substrate and the different organs of B. longifolia among different habitats. The C, N, P concentrations and C ∶ N, C ∶ P, N ∶ P ratios in the soil of forest floor were lower than those of epiphytic substrate in trunk. The C, N, P stoichiometry in substrate of the trunk base was intermediate the two. The B. longifolia individuals in the epiphytic habitat showed higher N and P concentrations, but lower C ∶ N, C ∶ P and N ∶ P ratios than those in the terrestrial habitat, which indicated that the epiphytic individuals of B. longifolia showed low nutrient use efficiency. In the three habitats, the N concentration and N:P ratio in leaves of B. longifolia were significantly lower than those of the roots, while C ∶ N ratio was higher than that of the roots. The homeostasis values of N, P and N ∶ P in leaves of B. longifolia were stronger than root, and decreased in the order of HN∶P> HN> HP. The weak stoichiometric homeostasis of root indicated that B. longifolia maintained relatively stable metabolic activities of leaf by adjusting the absorption and elemental composition of roots. In conclusion, facultative epiphytes adapt to habitat shifts by adjusting their nutrient uptake and utilization strategies among different habitats and stoichiometric homeostasis between leaves and roots. These findings enrich the theory of plant ecological stoichiometry, and also provide a scientific basis for understanding the formation and maintenance mechanism of biodiversity in montane forest ecosystems, as well as the protection and management of montane forest resources.