Light affects the resistance of native plant communities to Solidago canadensis with low invasion degrees

Light is an important factor for plant growth, and native plant communities are frequently invaded by alien plants to varying degrees. However, little is known about the effect of lighting on the resistance of native plant communities to alien plants with different degrees of invasion. We assessed the interactive effects of light condition and invasion degree on the growth of the invasive plant Solidago canadensis, the characteristics of the native plant communities and the invasion success of S. canadensis through both a field survey and greenhouse experiment. The field survey data showed that shading decreased the biomass of both S. canadensis and the native plant communities. However, it improved the relative dominance and thus, the invasion success of S. canadensis under the low and moderate invasion degrees but not at the high invasion degree. The data of the greenhouse experiment also showed that the native plant communities under shade were more susceptible to invasion by S. canadensis than the unshaded communities, particularly under the low and moderate invasion degree. In summary, we found that shading can weaken the resistance of native plant communities to alien plant invasions when there is a minimal invasion degree. These results underscore that managers need to be more attentive to the invasion of S. canadensis in sheltered environments. These findings provide a scientific reference to manage and control invasion by S. canadensis.