Soil conditioning effects of native and exotic grassland perennials on the establishment of native and exotic plants

Background and Aims: Semi-natural grasslands can combine biomass production with provision of multiple ecosystem services. Unfortunately, grassland establishment can be unpredictable and vulnerable to exotic plant invasion, potentially due to soil legacies from previous cultivation. Native plants could mitigate these legacies by changing soil attributes and facilitating other native grassland species. However, facilitation may be affected by nitrogen (N) fertilization, added during and after establishment. Methods: We conditioned soils in a former maize-soybean field for 3 years using multiple native or exotic perennial species or a maize-soybean rotation. Half of each plot received N fertilizer. Native and exotic grassland perennials were grown on these conditioned soils in the greenhouse, with N added to half of the pots, and biomass was measured. Results: Consistent facilitation of native species by other natives was not observed, nor did invasive species facilitate other invasives. Soil conditioning affected individual plant species’ biomass in several instances. Field N addition had little effect on plant biomass, while greenhouse N addition increased native more than exotic plant biomass, but did not alter the overall pattern of facilitation. Conclusions: Native plants failed to facilitate native prairie establishment in this work, suggesting resistance to conditioning on former intensive, high-input agricultural soils.