北方农牧交错带草木犀属外来植物沿公路分布和扩展的影响因素探讨

公路的建设给原有的生态系统带来人为干扰和影响，公路建筑材料的运输给外来植物的引入带来风险，公路修建以及环境因子则影响外来物种的建植和扩繁。选择北方农牧交错带典型的柏油公路，对草木犀属（Melilotus）外来植物沿公路的入侵状况进行样带调查，以探讨外来植物沿公路分布和扩散的影响因素。结果表明：公路两侧的土地利用方式是影响草木犀属植物分布的主要因素，路旁有农田的地段中，草木犀属植物的分布密度要显著大于有草地的地段（P<0.05）。距离则是影响草木犀属植物分布密度的重要因素，随着从路基到路旁生境距离的增加，草木犀属的分布密度呈显著下降趋势（P<0.05）。此外，公路的走向也影响草木犀属植物的分布，草木犀属在下风向的分布密度显著大于上风向的分布密度（P<0.05）；公路两旁高大树木的遮阴同样影响草木犀属植物沿公路的分布，遮阴环境影响草木犀属一年生植物的密度（P<0.05），但对于二年生植株没有显著影响。

Distribution and Dispersal of Alien Sweet Clover along Roadside in An Agro-pastoral Ecotone of Northern China

The construction of road introduces anthropogenic disturbance to the original ecological system. Transportation of construction material increases the risk of exotic plant invasion. The road changes the structure of original land and creates new habitat for the establishment and propagation of exotic plant. The distribution and dispersal of exotic sweet clover along roadsides were investigated in an agro-pastoral ecotone of northern China. Results showed that the utilization pattern of land adjacent to the road was a primary impact factor of the distribution and dispersal of sweet clover. The density of sweet clover near cropland was significantly greater than that near grassland. Distance was another impact factor of the distribution and dispersal of sweet clover. The density of sweet clover decreased significantly with the increase of distance from subgrade to roadside. Direction of road also affected the distribution and dispersal of sweet clover. There was a greater density in the downwind area than in the upwind area. Meanwhile, the shaded condition of road affected the establishment and development of sweet lover as well. Data showed that the density of annual sweet clover was influenced greatly under different shade conditions, whereas the density of biennial sweet clover was not affected. This survey study provides basic information for the further prevention and control of sweet clovers or other exotic species along roads in an agro-pastoral ecotone of northern China.