黄河三角洲不同湿地群落氮磷化学计量特征及其生境适应策略

Characteristics of N:P stoichiometry and the adaptation strategies for different coastal wetland communities in the Yellow River Delta

选取黄河三角洲滨海湿地盐地碱蓬(Suaeda salsa)、芦苇(Phragmites australis)和柽柳(Tamarix chinensis)3种典型植物群落为研究对象,研究了土壤-植物N、P元素的空间分布格局及N/P化学计量学特征。结果表明:盐地碱蓬地上部分N含量,地下部分N、P含量均小于芦苇和柽柳群落,柽柳地上部分P含量、N/P值均大于芦苇和盐地碱蓬群落。3种典型湿地群落N含量均呈现出地上部分大于地下部分的规律,说明植物会将有限的氮资源优先分配给地上部分光合器官;盐地碱蓬与柽柳地上和地下部分磷含量变化趋势相反,这种差异说明处在不同群落演替阶段的植物生活史策略不同。与木本植物柽柳不同,草本植物芦苇和盐地碱蓬N/P均表现出地上部分大于地下部分的特征,这与草本植物地上部分相对生长速率较大有关。土壤中N含量、N/P垂直变化趋势一致,均随着土层深度的增加而显著降低,但土壤磷的垂直变化特征不明显。相关分析显示,土壤(源)-植物(库)之间N、P相关性较弱,说明除了土壤条件,滨海湿地氮磷化学计量格局还与植物自身的生理调节有关。

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, Phrag- mites 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 under- ground 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 en- vironments. Unlike the woody species T. chinensis, the above,round 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 along the vertical soil profile. The weak correlations between the top soil（source） organs （pool） suggested that physiological accommodation of coastal wetland plants roles in N/P stoichiometric regulation besides soil conditions. P were found and the plant played some