Ecosystem functioning in urban grasslands: the role of biodiversity, abiotic and biotic novelty

We evaluated the relationship between biodiversity, abiotic and biotic novelty and ecosystem functioning based on in situ measurements in non-manipulated grasslands along an urbanization gradient in Berlin. We measured plant aboveground biomass (AGB), intrinsic water-use efficiency (iWUE) and 15N enrichment factor (δ15N) as proxies for biomass production, water and N cycling, respectively. The measurements were done for the whole plant community, for plants with different introduction status, plants belonging to different functional groups and two single species: Calamagrostis epigejos and Plantago lanceolata. We found that approximately one third of the forbs were alien to Berlin and theymade up around 13% of the whole community aboground biomass. Nonetheless, community aboveground biomass was positively correlated with plant-species richness . In contrast, iWUE and δ15N were mostly correlated to urban parameters associated to abiotic novelty.