Enhancing wasteland vegetation by adding ornamentals: Opportunities and constraints for establishing steppe and prairie species on urban demolition sites

Abstract

Following economic or demographic decline, many cities undergo extensive structural changes which often lead to large wasteland areas. Adding aesthetically attractive ornamental species to such sites has been proposed as a low cost approach to integrate wastelands into urban greenspace systems and enhance their acceptance by residents. Species from North American prairies and Eurasian steppes are expected to persist on urban sites despite low maintenance, but this idea has not yet been tested under Central European conditions. On urban demolition sites in Berlin, we established a randomised block design with mixtures of introduced species from either tall grass prairies or steppes. To test a low cost approach, the sites were mown once in autumn and never irrigated. Steppe species showed significantly higher mean survival rates (61%) than prairie species (19%). Competition from co-occurring wasteland species adversely affected prairie species but not steppe species. The second year after planting, survival rates declined due to a severe summer drought. Steppe species likely performed better because, in their native range, drought stress in spring and summer is common. Contrasting, prairie species are adapted to high precipitation during their major development period in North America. Nevertheless, three prairie and eight steppe species showed mean establishment rates >50% and obviously coped with the severe site conditions. Our results demonstrate opportunities for adding ornamentals to wastelands. In the face of a limited water supply, using robust steppe species appears most promising. Integrating regular irrigation into maintenance schemes could enhance the establishment of prairie species.