von der Lippe Moritz, Kowarik Ingo
Institute of Ecology, Technical University of Berlin, Rothenburgstr.12, D-12165 Berlin, Germany.
Conserv Biol. 2007 Aug;21(4):986-96. doi: 10.1111/j.1523-1739.2007.00722.x.
Roadsides are preferential migration corridors for invasive plant species and can act as starting points for plant invasions into adjacent habitats. Rapid spread and interrupted distribution patterns of introduced plant species indicate long-distance dispersal along roads. The extent to which this process is due to species' migration along linear habitats or, alternatively, to seed transport by vehicles has not yet been tested systematically. We tested this by sampling seeds inside long motorway tunnels to exclude nontraffic dispersal. Vehicles transported large amounts of seeds. The annual seed rain caused by vehicles on the roadsides of five different tunnel lanes within three tunnels along a single urban motorway in Berlin, Germany, ranged from 635 to 1579 seeds/m(2)/year. Seeds of non-native species accounted for 50.0% of the 204 species and 54.4% of the total 11,818 seeds trapped inside the tunnels. Among the samples were 39 (19.1%) highly invasive species that exhibit detrimental effects on native biodiversity in some parts of the world. By comparing the flora in the tunnel with that adjacent to the tunnel entrances we confirmed long-distance dispersal events (>250 m) for 32.3% of the sampled species. Seed sources in a radius of 100 m around the entrances of the tunnels had no significant effect on species richness and species composition of seed samples from inside the tunnels, indicating a strong effect of long-distance dispersal by vehicles. Consistently, the species composition of the tunnel seeds was more similar to the regional roadside flora of Berlin than to the local flora around the tunnel entrances. Long-distance dispersal occurred significantly more frequently in seeds of non-native (mean share 38.5%) than native species (mean share 4.1%). Our results showed that long-distance dispersal by vehicles was a routine rather than an occasional mechanism. Dispersal of plants by vehicles will thus accelerate plant invasions and induce rapid changes in biodiversity patterns.
道路两旁是入侵植物物种优先选择的迁移通道，并且可能成为植物入侵邻近栖息地的起点。外来植物物种的快速传播和间断分布模式表明其沿着道路进行了远距离扩散。这个过程在多大程度上是由于物种沿着线性栖息地迁移，或者是由于车辆运输种子，尚未得到系统的检验。我们通过在长的高速公路隧道内采集种子来排除非交通传播，从而对此进行了测试。车辆运输了大量种子。在德国柏林一条城市高速公路上的三条隧道内，五个不同隧道车道的道路两旁，车辆造成的年种子雨范围为635至1579粒种子/平方米/年。在捕获到的隧道内的204个物种中，非本地物种的种子占50.0%，在总共11818粒种子中占54.4%。样本中有39种（19.1%）极具入侵性的物种，它们在世界某些地区对本地生物多样性产生了有害影响。通过比较隧道内的植物群落与隧道入口附近的植物群落，我们确认了32.3%的采样物种发生了远距离扩散事件（>250米）。隧道入口周围100米半径内的种子源对隧道内种子样本的物种丰富度和物种组成没有显著影响，这表明车辆远距离传播的影响很大。一致的是，隧道种子的物种组成与柏林的区域路边植物群落比与隧道入口周围的本地植物群落更相似。非本地物种的种子（平均占比38.5%）比本地物种的种子（平均占比4.1%）发生远距离扩散的频率明显更高。我们的结果表明，车辆远距离传播是一种常规而非偶然的机制。因此，车辆传播植物将加速植物入侵并导致生物多样性模式的快速变化。
