水、盐梯度下黄河三角洲湿地植物种的生态位

利用排序等方法将黄河三角洲湿地19个植物种在水深和土壤盐分梯度下依次排列，并分别划分为低、中、高水深（或土壤盐分）3个生态种组，分析了水、盐梯度下植物种的生态位宽度和生态位重叠.结果表明:水深梯度下，芦苇、盐地碱蓬等中水深生态种组植物种生态位宽度较大，香蒲、穗状狐尾藻等高水深生态种组植物种生态位宽度最小；土壤盐分梯度下，盐地碱蓬、柽柳等高土壤盐分生态种组植物种生态位宽度较大，而中、低土壤盐分生态种组的植物种生态位宽度均较小.水深和土壤盐分梯度下的生态位重叠分别沿着植物种在两种梯度上的排序而规律变化，通常同一生态种组内部植物种的生态位重叠较大，不同生态种组植物种的生态位重叠较小.黄河三角洲湿地植物种在水深、土壤盐分梯度下的生态位分化现象，可能有助于阐释湿地植物共存及带状分布的形成机制.

Niches of plant species in wetlands of the Yellow River Delta under gradients of water table depth and soil salinity.

Ordination methods were used to arrange in turn the 19 plant species in wetlands of the Yellow River Delta under gradients of water table depth and soil salinity, and to classify them into three ecological species groups, i. e. low, medium, and high water table depth/soil salinity ecological species groups. Their niche breadths and niche overlaps under the two gradients were also analyzed. The results indicated that for the gradient of water table depth, the species in medium water table depth ecological species group, such as Phragmites australis and Suaeda salsa, occupied a broad niche breadth, and those in high water table depth ecological species group, such as Typha orientalis and Myriophyllum spicatum, occupied the narrowest niche breadth. For the gradient of soil salinity, the species in high soil salinity ecological species group, such as Suaeda salsa and Tamarix chinensis, occupied a broad niche breadth, while those belonging to the medium and low soil salinity ecological species groups occupied a narrow niche breadth. The niche overlaps changed regularly along the gradients of water table depth and soil salinity. In general, the niche overlaps between the plant species of the same ecological species groups were large, whilst those between the plant species of different ecological species groups were small. Niche differentiations of the plant species under the gradients of water table depth and soil salinity might promote species coexistence, and contribute to the explanation of plant zonation mechanisms in this Delta.