The post-invasion success of alien plant species is determined by many biotic and abiotic factors, but no study has tested the interactive effect of nutrient availability, fluctuating nutrient supply and parasitic plants. Testing this effect is important because parasitic plants are proposed as a promising agent for biocontrol of alien plant invasions. We constructed an experimental native community under constant or fluctuating conditions as well as high or low nutrient availability and let them be invaded by an alien annual plant Bidens pilosa or not and parasitized by Cuscuta australis or not. High nutrient availability significantly increased the invasion success of B. pilosa (as indicated by its increased biomass fraction, i.e., invader biomass divided by total biomass of all plants) by benefiting the invader more than the native plant community. Fluctuating nutrient supply also significantly enhanced the invasion success of B. pilosa by suppressing the growth of the natives while improving that of the invader. Parasitism by C. australis decreased the growth of the invader and thus its invasion success in the native community when nutrient availability was low and fluctuating, but parasitism had little impact under other nutrient conditions. Our study offers further evidence that high and fluctuating nutrient availability can increase the invasion success of alien plant species in native plant communities, but also demonstrates that the impact of parasitic plants depends on environmental conditions. Thus, reducing nutrient loading and the extent of fluctuating nutrient supply can help native plant communities resist alien plant invasions, but introducing parasitic plants may only be successful if reduced loads are also fluctuating.

外来植物物种入侵后的成功取决于许多生物和非生物因素，但尚无研究测试养分有效性，养分供应波动和寄生植物的相互作用。测试这种效果非常重要，因为提出了将寄生植物作为生物控制外来植物入侵的有前途的药物。我们在恒定或波动的条件下以及高或低的养分利用率下建立了一个实验性的原生社区，让它们被外来一年生植物Bidens pilosa入侵和不被外来一年生Cuscuta australis寄生。高养分利用率显着提高了B. pilosa的入侵成功率（如其增加的生物量所占比例，即入侵者生物量除以所有植物的总生物量所表明），从而使入侵者比本地植物群落受益更多。营养物质供应的波动还通过抑制本地人的生长，同时改善了入侵者的生长，也显着提高了B. pilosa的入侵成功率。澳大利亚寄生虫当养分利用率低且波动时，可减少入侵者的生长，从而减少入侵者在本地社区的入侵，但是在其他养分条件下，寄生寄生几乎没有影响。我们的研究提供了进一步的证据，表明养分利用率高且波动大，可以增加外来植物物种在本地植物群落中的入侵成功率，但同时也表明寄生植物的影响取决于环境条件。因此，减少养分含量和养分供应的波动范围可以帮助本地植物群落抵御外来植物的入侵，但是只有在降低的养分含量也在波动的情况下，引入寄生植物才可能成功。