黄河口不同氮基质碱蓬种子萌发及幼苗生长对盐分及氮输入的响应

2014年4-11月,选择黄河入海口北部滨岸高潮滩的碱蓬湿地为研究对象,基于野外原位氮负荷增强模拟试验(N0,无额外氮输入;N1,低氮输入;N2,中氮输入;N3,高氮输入),获取相应的不同氮基质种子(S0,S1,S2和S3),以研究其发芽率以及幼苗生长状况对不同盐分胁迫和氮浓度交互作用的响应。结果表明,不同氮负荷影响下碱蓬成熟种子中的氮含量整体表现为S2S0S1S3,中氮输入更利于种子中氮养分的累积。盐分和氮交互作用下4种氮基质种子的发芽率总体表现为S2S1S0S3(P0.05),S2在不同盐分胁迫下的发芽率最高,幼苗的生长状况也最好。随着盐分的增加,4种氮基质种子的发芽率及幼苗生长状况均受到一定程度的抑制,但较低的盐分有助于其幼苗长度的增长,且随着氮输入量的增加这种抑制作用可得到一定程度缓解。盐分胁迫、氮浓度和种子类型作为单独因素出现时对碱蓬的发芽率、幼苗长度、鲜重和干重均产生显著影响,除幼苗长度受氮浓度和盐分胁迫交互作用的影响达到显著水平外(P0.05),其他因子交互作用对诸生态指标的影响并不明显。研究发现,不同氮输入处理不仅改变了原生环境碱蓬种子的氮含量,而且也使这些具备不同氮基质的种子对不同盐分胁迫与氮浓度环境具有不同的生态适应对策,中氮输入下的碱蓬种子(S2)无论在萌发率还是在幼苗生长状况上均优于其他氮基质的种子。未来,随着黄河口新生湿地氮养分供给的不断增加,当湿地氮养分达到中氮水平时,将更有利于碱蓬种子的萌发以及幼苗的生长,当氮养分达到更高水平时,碱蓬种子的萌发以及幼苗生长可能会受到一定程度的抑制。

Germination and seedling growth of different N-substrate seeds of Suaeda salsa subjected to salinity stress and nitrogen loading in the newly created marshes of the Yellow River estuary, China

From April to November, 2014, an in situ nitrogen (N) loading experiment (N0, no N loading treatment; N1, low N loading treatment; N2, moderate N loading treatment; and N3, high N loading treatment) was conducted in a Suaeda salsa community in high marshes in the northern Yellow River estuary. Different N-substrate seeds were sampled in the corresponding N treatment plots (S0, S1, S2, and S3). The objective of this study was to explore the responses of germination and seedling growth of different N-substrate seeds of S. salsa to salinity stress and nitrogen loading. Results showed that the N content in seeds sampled from different N loading plots were in the order of S2 > S0 > S1 > S3 and compared to other N loading treatments, the N2 treatment was more favorable for N accumulation in seeds. The interaction of salinity stress and N concentrations showed substantial effects on germination rate of the four N-substrate seeds, following the sequence of S2 > S1 > S0 > S3 (P > 0.05). Under different salinity stresses, the germination rate and seedling growth of S2 were the best. With increasing salinity, the germination rate and seedling growth of the four N-substrate seeds were generally inhibited, but at lower salinity, conditions were favorable for seedling elongation and the inhibitory effect could be alleviated by high N loading. The combined effect of salinity stress, N concentration, and seed types had significant impacts on germination rate, seedling length, and fresh and dry weight. Except for seedling length, the interaction of the three factors demonstrated no significant influences on the above ecological traits. This study found that the N loading treatments not only altered the nitrogen content of S. salsa seeds in the primary environment, but also resulted in N-substrate seeds that presented different adaptation strategies to nitrogen loading and salinity stress. Compared to other N-substrate seeds, S2 showed great advantages in germination rate and seedling growth. In the future, nutrient loading will be increasingly utilized in the newly created marshes of the Yellow River estuary. It was concluded that, as the nutrient reached the N2 level, germination and seedling growth of S. salsa would be greatly promoted. If nutrients reached higher levels, germination and seedling growth would, to some extent, be inhibited.