潮滩冲淤扰动下外来与乡土红树植物幼苗稳定性差异

引种外来树种是我国各地在红树林修复实践中常用的措施。由于更容易在困难立林地存活, 外来树种被认为更具竞争优势。为弄清外来与乡土红树植物物种在困难立林地存活能力的差异及其原因, 本研究选取典型外来引种先锋树种拉关木(Laguncularia racemosa)与乡土先锋植物白骨壤(Avicennia marina)为研究对象, 通过控制实验探究潮滩冲淤扰动条件下幼苗稳定性差异及其形成机制。结果表明, 幼苗抗侵蚀能力与幼苗根冠比显著正相关, 泥沙淤积抑制幼苗根系生长, 而底床侵蚀则促进根系伸长。与白骨壤相比, 拉关木幼苗的主根更长, 根冠长度比更大, 更能抵抗底泥的侵蚀扰动, 且通过根系伸长以增强幼苗稳定性的能力也更强。拉关木幼苗比白骨壤更能适应潮滩冲淤扰动, 其竞争优势从幼苗阶段就已经建立。本研究结果可为红树林修复实践中树种和宜林地的选择提供参考, 亦可为评估外来红树物种入侵风险评价提供依据。

Performance of exotic and native mangrove seedlings under accretion/erosion disturbances on tidal flats

Exotic species are only used in some places in China for mangrove restoration, as they often perform better than native species on these desired restoration sites often with highly stressful habitats. Here, we conducted a mesocosm experiment to detect the differences of survivability between exotic and native mangrove seedlings under accretion/erosion disturbances on tidal flats, using exotic species Laguncularia racemosa and native pioneer species Avicennia marina as examples. Our results demonstrated that for both species the erosion resistance of seedlings correlated positively with root-to-shoot length ratio. Sediment accretion disturbance inhibited the root development of seedlings so that the root-to-shoot length ratio increased, while sediment erosion promoted root elongation with the root-to-shoot length ratio decreased. Compared with the native species A. marina, exotic species L. racemosa seedlings have greater root-to-shoot ratio, and are thus more resistant to erosion with better adaptability to sediment dynamics via root elongation. Our study indicates that the exotic species L. racemosa are more adaptable to erosion disturbances on tidal flats than the native species A. marina. These findings shed light on the selection of tree species and suitable planting sites for mangrove restoration, and might provide helpful insights into assessing the risk of species invasion in mangrove ecosystems.