Road corridors are important conduits for plant invasions, and an understanding of the underlying mechanisms is necessary for efficient management of invasive alien species in road networks. Previous studies identified road type with different traffic volumes as a key driver of seed dispersal and abundance of alien plants along roads. However, how the intensity of traffic interacts with the habitat features of roadsides in shaping invasion processes is not sufficiently understood. To elucidate these interactions, we analyzed the population dynamics of common ragweed (Ambrosia artemisiifolia L.), a common non-indigenous annual species in Europe and other continents, in a regional road network in Germany. Over a period of five years, we recorded plant densities at roadsides along four types of road corridors, subject to different intensities of traffic, and with a total length of about 300 km. We also classified roadsides in regard to habitat features (disturbance, shade). This allowed us to determine corridor- and habitat-specific mean population growth rates and spatial-temporal shifts in roadside plant abundances at the regional scale. Our results show that both traffic intensity and roadside habitat features significantly affect the population dynamics of ragweed. The combination of high traffic intensity and high disturbance intensity led to the highest mean population growth whereas population growth in less suitable habitats (e.g. shaded roadsides) declined with decreasing traffic intensity. We conclude that high traffic facilitates ragweed invasion along roads, likely due to continued seed dispersal, and can compensate partly for less suitable habitat features (i.e. shade) that decrease population growth along less trafficked roads. As a practical implication, management efforts to decline ragweed invasions within road networks (e.g. by repeated mowing) should be prioritized along high trafficked roads, and roadside with disturbed, open habitats should be reduced as far as possible, e.g. by establishing grassland from the regional species pool.

中文翻译：

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交通强度和栖息地特征的相互作用塑造了区域路网中外来入侵物种（Ambrosia artemisiifolia）的入侵动态。

道路走廊是植物入侵的重要渠道，对底层机制的理解对于有效管理道路网络中的外来入侵物种是必要的。先前的研究将交通量不同的道路类型确定为种子散布和道路上外来植物丰富的主要驱动力。然而，在形成入侵过程中，交通强度如何与路边的栖息地特征相互作用尚不清楚。为了阐明这些相互作用，我们在德国的区域公路网中分析了豚草（Ambrosia artemisiifolia L.）的种群动态，该豚草是欧洲和其他大洲的常见非本地一年生物种。在五年的时间里，我们记录了沿四种类型的道路走廊的路边的植物密度，视交通强度而定，总长度约为300公里。我们还根据生境特征（干扰，阴影）对路边进行了分类。这使我们能够确定特定走廊和栖息地的平均人口增长率以及路边植物丰度在区域范围内的时空变化。我们的研究结果表明，交通强度和路边栖息地特征都对豚草的种群动态有显着影响。高交通强度和高干扰强度的结合导致最高的平均人口增长，而在交通不便的地区，不适合居住的栖息地（如路边的阴影）的人口增长却下降了。我们得出的结论是，高流量会促使豚草入侵公路，这可能是由于种子不断散播造成的，并可以部分补偿不太合适的栖息地特征（即阴影），这些特征会减少人流稀少的道路上的人口增长。实际上，应优先考虑在人流密集的道路上减少道路网络中豚草入侵的管理工作（例如通过反复割草），并应尽可能减少路边混乱，开放的生境，例如通过从该地区建立草地物种库。