天津独流减河河口不同植物群落的生态化学计量学特征

The stoichiometric characteristics of different plant communities in the Duliujian River estuary

以独流减河河口及其潮上带区域的互花米草(Spartina alterniflora Loisel.)、芦苇[Phragmites australis (Cav.)Trin. ex Steud.]和盐地碱蓬[Suaeda salsa (Linn.) Pall.]群落为研究对象,探究该区域不同植物群落碳(C)、氮(N)、磷(P)、硫(S)化学计量学特征及其驱动因素.结果显示,互花米草和芦苇地上部分C含量显著高于盐地碱蓬,而根系中的C含量则反之,显示了植物不同的C分配策略. N、P主要分布在植物地上部分光合器官,N含量与全国湿地植物和全球植物的含量水平相当,但P含量显著高于全国湿地植物和全球植物的含量. S在芦苇和盐地碱蓬体内主要分布在地上部分,而互花米草的S则主要分布在根系中,这有利于互花米草拓展地下空间,从而加速其入侵.互花米草的C/P和芦苇的C/N均显著高于其他植物,说明前者具有较高的P利用效率,而后者的N利用效率较高.河口潮上带芦苇和盐地碱蓬叶片N/P分别为7.32和8.90,而潮间带互花米草叶片N/P为14.45,根据生长速率假说,认为生长速率并不是互花米草与芦苇和盐地碱蓬竞争的有效手段,而高的P利用效率为互花米草种群的扩张创造了条件.相关性分析表明,在独流减河河口地区土壤P和盐度是植物体内元素平衡和生态化学计量变化的重要影响因子.综上,天津独流减河河口湿地正经历着由N限制向P限制的转变,P元素在该区域植物生长和演替方面起着重要作用.

To elucidate plant community succession and stoichiometric balance in estuarine and coastal wetlands under nutrient limiting conditions, the carbon(C), nitrogen(N), phosphorus(P), and sulfur(S) stoichiometry and their potential drivers for different plant communities in the Duliujian River estuary were studied. The concentrations of C, N, P, and S in different organs(leaf, stem, and root) of Suaeda salsa(Linn.) Pall, Phragmites australis(Cav.) Trin. ex Steud. and Spartina alterniflora Loisel., and environmental factors of soil C, soil N, soil P, soil S, salinity, and pH in the surface soil(0–10 cm) were determined.The results showed that the content of C in the aerial organs of S. alterniflora and P. australis were significantly higher than that in S. salsa, but the opposite occurred in the root, indicating the different carbon allocation strategies for these plants. N and P were mainly distributed in the aerial photosynthetic organs of plants. The contents of N in the Duliujian River estuary was almost equivalent to that of the vegetation in global and wetland vegetation in China, but the contents of P in the Duliujian River estuary were significantly higher than that of global wetlands or those in vegetation in China. S was mainly distributed in the aerial organs in S. salsa and P. communis, whereas distributed in the roots of S. alterniflora, indicating that S was conducive in the promotion of the mutual flowering and the acceleration of the their invasion. The C/P ratio for S. alterniflora was highest and the C/N ratio for P. communis was the highest, suggesting that S. alterniflora had higher P use efficiency and P.communis had higher N use efficiency. In the leaf, the N/P ratios of P. communis and S. salsa in the Supra tidal zone were 7.32 and 8.90, respectively, but the that of S. alterniflora in the intertidal zone was 14.45. According to the Growth Rate Hypothesis,the growth rate was not an effective means of competition between S. alterniflora and P. australis and S. salsa. However, the higher N use efficiency accelerated the invasion of S. alterniflora. Meanwhile, the correlation analysis indicated that soil P and salinity were important factors affecting the elemental balance in plants and stoichiometry changes in the Duliujian River estuary. We conclude that the Duliujian River estuary is being transformed from N limitation to P limitation. The P element plays an important role in plant growth and succession in this area.