关键词: 树种幼苗, 季节差异, 海拔梯度

Abstract: In order to study the spatial distribution patterns of nitrogen (N) and phosphorus (P) and the stoichiometric characteristics of three typical plant communities (Suaeda salsa, Phragmites australis and Tamarix chinensis) of coastal wetlands in the Yellow River Delta, soil and plant samples were collected. The results showed that the contents of aboveground N and underground N and P of S. salsa were lower than those of P. australis and T. chinensis, while the aboveground P content and N/P ratio of T. chinensis were higher than those of P. australis and S. salsa. For the three wetland communities, the N content of aboveground biomass was significantly higher than that of underground biomass, indicating that N tended to be allocated to the aboveground photosynthetic organ in the Nlimited habitat. However, an opposite trend existed for the P contents of above and underground biomass of T. chinensis and S. salsa, which revealed that species in different successional status would adopt different strategies to adapt to various environments. Unlike the woody species T. chinensis, the aboveground biomass of P. australis and S. salsa had higher N/P ratios than the underground biomass, and this was possibly related to the high relative growth rate of the aboveground organs of herbaceous species. The soil N content and N/P ratio decreased with  the soil depth increasing, while no obvious changes of soil P were found along the vertical soil profile. The weak correlations
 between the top soil (source) and the plant organs (pool) suggested that physiological accommodation of coastal wetland plants played some roles in N/P stoichiometric regulation besides soil conditions.

Key words: altitudinal gradient, seasonal variation, tree seedlings