1. The dispersal of aquatic plant propagules is highly facilitated in streams due to flow. As many aquatic plants predominantly spread through vegetative propagules, the specific retention and thus drift distance of dispersed plant fragments largely contribute to the rapid spread along the course of a stream.
2. We determined fragment retention for four aquatic plant species (Elodea canadensis, Myriophyllum spicatum, Ceratophyllum demersum, Salvinia natans; representing four different common morpho‐structural groups) in sections of small to medium‐sized German streams with different levels of stream sinuosity.
3. The number of fragments showed a logistic decline over drift distance. In two small streams, 90% of drifting fragments were retained at distances (D₉₀) of only 5–9 m and 19–70 m, while higher D₉₀ values of 116–903 m and 153–2,367 m were determined for sections of a medium‐sized stream. The likelihood of retention thereby decreased significantly with increasing stream size and was reduced in straightened stream sections.
4. Differences in retention were more strongly related to fragment buoyancy rather than fragment size and morphology. Increasing buoyancy significantly lowered the likelihood of fragment retention over drift distance by a factor of 3–8, whereas contrasting effects were documented for size and morphology of fragments.
5. The relevance of different obstacles was highly stream section‐specific and depended on obstacle abundance, distribution, and the degree of submergence/emergence.
6. Our findings elucidate the dynamic retention patterns of plant fragments and highlight the strong interplay between extrinsic (stream) and intrinsic (fragment) properties. We conclude that straightened lowland streams of intermediate size promote the rapid dispersal of invasive aquatic plants and are particularly prone to invaders producing large amounts of small and highly buoyant plant fragments. Information on the species‐specific fragment colonisation dynamics in the field is further required to improve our understanding of the vegetative dispersal capacity of invasive aquatic plants in stream ecosystems.

中文翻译：

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顺其自然：碎片保留模式塑造了低地溪流中水生植物的营养扩散

1. 由于流动，在水流中水生植物繁殖体的分散非常容易。由于许多水生植物主要通过营养繁殖体传播，分散的植物碎片的比保留率和因此的漂移距离在很大程度上促进了沿水流的快速传播。
2. 我们确定四个水生植物物种片段保留（伊乐藻，狐尾藻，金鱼藻，槐叶苹;在具有不同水平的流弯度的中型德国流的小部分表示四个不同的常见形态内的结构基团）。
3. 碎片数量在漂移距离上显示出逻辑下降。在两条小溪中，90％的漂移碎片保留在仅5–9 m和19–70 m的距离（D ₉₀）上，而对于D剖面，确定的较高D ₉₀值为116–903 m和153–2,367 m。中型流。保留的可能性因此随流尺寸的增加而显着降低，而在拉直的流段中降低。
4. 保留的差异与碎片的浮力更密切相关，而不是与碎片的大小和形态有关。浮力的增加显着降低了在漂移距离上保留碎片的可能性，降低了3–8倍，而据记录，碎片的大小和形态形成了相反的影响。
5. 不同障碍物的相关性是特定于河流断面的，并且取决于障碍物的丰度，分布以及淹没/涌出的程度。
6. 我们的发现阐明了植物碎片的动态保留模式，并强调了外部（河流）和内在（碎片）特性之间的强烈相互作用。我们得出的结论是，中等大小的拉直的低地溪流促进了入侵性水生植物的快速扩散，特别容易使入侵者产生大量的小型且高度浮力的植物碎片。还需要有关田间物种特异性片段定居动态的信息，以增进我们对河流生态系统中入侵水生植物营养分散能力的了解。