Alkaline habitat for vegetated roofs? Ecosystem dynamics in a vegetated roof with crushed concrete-based substrate

• Published in: Ecological engineering Vol. 157; p. 105970
• Main Authors: Jauni, Miia, Kuoppamäki, Kirsi, Hagner, Marleena, Prass, Marju, Suonio, Taina, Fransson, Ann-Mari, Lehvävirta, Susanna
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.2020; Elsevier BV
• Subjects: Abundance; Composting; Composts; Concrete; Crushing; Ecology; Ecosystem dynamics; Ecosystem services; Ecosystems; Ekologi; Endangered plants; Endangered species; Flowers & plants; Geographical distribution; Green roof; Introduced species; Invasive species; Landscape Architecture; Landskapsarkitetktur; Nature-based solutions, growth media; pH effects; Phosphorus; Plant diversity; Planting; Plants; Rare species; Recycled materials; Roofing; Roofs; Runoff; Runoff quality; Soil; Soils; Substrates; Survival; Vegetation; Vegetation dynamics; Green roof; Recycled materials; Nature-based solutions, growth media; Vegetation dynamics; Runoff quality
• ISSN: 0925-8574; 1872-6992; 1872-6992
• DOI: 10.1016/j.ecoleng.2020.105970

Using local and recycled materials is a sustainable way to establish a vegetated roof. In order to understand how the roof ecosystem functions and returns ecosystem services, it is important to study vegetation, soil organisms and runoff quality. We established a vegetated roof experiment based on a substrate containing lightweight crushed concrete, an alkaline side product from a concrete factory, mixed with compost. This five-year experiment in southern Finland tested how planting method (pre-grown vegetation mats vs. pot planting), compost content (20% vs. 40%, fresh volume), and substrate depth affect the cover and diversity of plants, the abundance of soil animals and the quality of runoff. Although the substrate had a high pH (7.3–11.8), many vascular plants were able to survive and establish viable populations. The planting method had a strong effect on plant diversity and the cover of individual species because the vegetation mats became dominated by the invasive, non-native Phedimus hybridus. Establishment with pot plants in turn provided bare ground that was colonised by spontaneous non-invasive species. This resulted in higher diversity, and a more even distribution of species. The amount of compost had only a weak impact on vegetation, whereas high pH generally reduced plant abundance and diversity. The concentrations of total phosphorus and total nitrogen in runoff were low as compared to values reported from many other vegetated roofs, were not affected by compost content and decreased over time. In summary, the high-pH substrate based on recycled materials is an environmentally responsible choice, suitable for a wide variety of plants, even rare and endangered species. •Crushed lightweight concrete is suitable as part of vegetated roof substrate.•Many vascular plant species survive despite the high pH of the substrate.•High pH of concrete reduced phosphorus leaching.•A non-native Phedimus hybridus dominated pre-grown vegetation mats.•Roof ecosystem dynamics exhibited high year-to-year variability.