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- Fakultät AuL (6)
Da urbane Räume besonders von den Folgen des Klimawandels wie Hitzewellen und Starkregen betroffen sind, gibt es vielerorts einen steigenden Bedarf an grüner Infrastruktur bei gleichzeitiger Verringerung des Anteils an Grünflächen durch Bebauung. Extensive Dachbegrünungen können bei fachgerechter Ausführung einen Beitrag zur Verbesserung des Stadtklimas leisten. Werden Dächer mit gebietseigenen Wildpflanzenarten begrünt, so können sie auch zur Förderung regionaltypischer Pflanzen- und Tierarten beitragen. Diese Art der Dachbegrünung ist bislang jedoch wenig erprobt. Dieser auf Ergebnissen des EFRE-Projekts RooBi (Roofs for Biodiversity) basierende Leitfaden für extensive Dachbegrünungen mit gebietseigenen Wildpflanzen soll Impulse für die Realisierung und weitere Erprobung dieser Form der Dachbegrünung geben. Vegetationstechnische Anforderungen, die Auswahl geeigneter Wildpflanzen für Dächer in Nordwestdeutschland und deren Pflege auf dem Dach werden beschrieben ebenso wie Hinweise zu Fördermöglichkeiten. Anhand von Praxisbeispielen wird aufgezeigt, mit welchen Methoden und Materialien sich extensive Dachbegrünungen mit Pflanzenarten nordwestdeutscher Sandmagerrasen umsetzen lassen und wie sich die Vegetation in den ersten Jahren entwickelt.
Der Leitfaden richtet sich an Menschen aus Wissenschaft und Praxis der Stadt- und Landschaftsplanung sowie des Garten- und Landschaftsbaus und des Naturschutzes.
Ecological restoration of an urban demolition site through introduction of native forb species
(2020)
Urban brownfields can provide habitats for endangered native plant species but may also support invasive non native species. The aim of our study was to develop and test different measures for the ecological restoration of an urban brownfield. We aimed to enhance native plant species richness by seeding two native forb seed mix tures containing 25 (HD-mixture) and 13 species (LD-mixture), respectively, without affecting spontaneously colonizing plant species of nature conservation value. Additionally, we tested the effects of species introduction and mowing on the establishment of invasive non-native plant species, woody species development, and per ennial grass dominance.
With establishment rates of 84% (HD) and 92% (LD) in the first study year and about 60% for both seed mixtures in the fourth year, species introduction was successful and led to rapid re-vegetation of the formerly bare brownfield. Although seeding did not result in increased species richness using either seed mixture, the dominance of perennial grasses was significantly reduced by the establishment of forb species from the HD mixture. Overall, we observed the spontaneous establishment of ten plant species of conservation value; seeding affected these species only temporarily, in the second year. Seeding (with either seed mixture) and mowing both resulted in reduced cover of woody species and a lower frequency of the invasive non-native Robinia pseudoa cacia.
Our study demonstrated the high nature conservation value of dry and nutrient-poor urban brownfields for spontaneously occurring threatened plant species. Further studies have to evaluate if the reduced cover of grasses and woody species through introduction of site-specific native forb species might increase these sites’ aesthetic value and broader acceptance of brownfields by urban residents.
Extensive green roofs (EGRs) offer several beneficial ecosystem services for sustainable urban development. However, most standard green roofs have been designed with species-poor plant mixtures containing non-native species. Aiming to increase the nature conservation values of EGRs, we developed and tested a vascular plant seed mixture including regionally occurring native sandy dry grassland species in experimental miniature roofs in Northwestern Germany (temperate oceanic climate) over 4 years. We tested the mixture at two seed densities (1 and 2 g/m2). Additionally, we tested seeding at 1 g/m2 and introducing raked plant material collected from an ancient dry grassland. The total establishment rates of sown species reached 92–96% in the first year, but dropped to 40–60% in the last 2 years, with the highest values for the plots with raked material. Twenty-four additional species (11 vascular, 7 lichen, and 6 moss species, including 7 red-list species) typical of sandy dry grasslands were introduced through the raked material. Vascular plants reached 60–70% cover in the second year. Severe drought periods in the third and the fourth year led to a strong decline of vascular plant cover then. As this cover was higher in the plots with raked material, we assume facilitative effects through the well-developed cryptogam layer containing a mix of pleurocarpous and acrocarpous mosses and lichens. Spontaneously establishing acrocarpous mosses in sown plots did not seem to provide this same function. We conclude that EGRs designed with regionally occurring sandy dry grassland plant species and especially the application of raked plant material from ancient grassland is a fruitful approach to increase the value of green roofs for native phytodiversity.