Agroecology, Department of Crop Sciences, Georg-August University, Grisebachstr. 6, 37077 Göttingen, Germany.
Proc Biol Sci. 2011 Nov 22;278(1723):3444-51. doi: 10.1098/rspb.2011.0268. Epub 2011 Apr 6.
Agricultural land use results in direct biodiversity decline through loss of natural habitat, but may also cause indirect cross-habitat effects on conservation areas. We conducted three landscape-scale field studies on 67 sites to test the hypothesis that mass flowering of oilseed rape (Brassica napus) results in a transient dilution of bees in crop fields, and in increased competition between crop plants and grassland plants for pollinators. Abundances of bumble-bees, which are the main pollinators of the grassland plant Primula veris, but also pollinate oilseed rape (OSR), decreased with increasing amount of OSR. This landscape-scale dilution affected bumble-bee abundances strongly in OSR fields and marginally in grasslands, where bumble-bee abundances were generally low at the time of Primula flowering. Seed set of Primula veris, which flowers during OSR bloom, was reduced by 20 per cent when the amount of OSR within 1 km radius increased from 0 to 15 per cent. Hence, the current expansion of bee-attractive biofuel crops results in transient dilution of crop pollinators, which means an increased competition for pollinators between crops and wild plants. In conclusion, mass-flowering crops potentially threaten fitness of concurrently flowering wild plants in conservation areas, despite the fact that, in the long run, mass-flowering crops can enhance abundances of generalist pollinators and their pollination service.
农业土地利用通过丧失自然生境直接导致生物多样性减少，但也可能对保护区产生间接的跨生境影响。我们在 67 个地点进行了三项景观尺度的实地研究，以检验以下假设：油菜（Brassica napus）大规模开花会导致作物田蜜蜂短暂稀释，并增加作物植物和草原植物对传粉者的竞争。毛蜂的丰度（草原植物报春花的主要传粉者，但也传粉油菜）随着油菜数量的增加而减少。这种景观尺度的稀释强烈影响了油菜田中的毛蜂丰度，而对草原的影响则较小，因为在报春花开花时草原上的毛蜂丰度通常较低。当半径 1 公里范围内的油菜面积从 0 增加到 15%时，报春花的结实率下降了 20%。因此，目前蜜蜂吸引力生物燃料作物的扩张导致作物传粉者短暂稀释，这意味着作物和野生植物之间的传粉者竞争加剧。总之，尽管大规模开花的作物从长远来看可以增加一般传粉者及其传粉服务的丰度，但它们可能会威胁到保护区内同时开花的野生植物的适应性。
