There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
The installation of green roofs, defined here as rooftops with a shallow soil cover
and extensive vegetation, has been proposed as a possible measure to mitigate the
loss of green space caused by the steady growth of cities. However, the effectiveness
of green roofs in supporting arthropod communities, and the extent to which they facilitate
connectivity of these communities within the urban environment is currently largely
unknown. We investigated the variation of species community composition (beta diversity)
of four arthropod groups with contrasting mobility (Carabidae, Araneae, Curculionidae,
and Apidae) on 40 green roofs and 40 extensively managed green sites on the ground
in the city of Zurich, Switzerland. With redundancy analysis and variation partitioning,
we (1) disentangled the relative importance of local environmental conditions, the
surrounding land cover composition, and habitat connectivity on species community
composition, (2) searched for specific spatial scales of habitat connectivity for
the different arthropod groups, and (3) discussed the ecological and functional value
of green roofs in cities. Our study revealed that on green roofs community composition
of high-mobility arthropod groups (bees and weevils) were mainly shaped by habitat
connectivity, while low-mobility arthropod groups (carabids and spiders) were more
influenced by local environmental conditions. A similar but less pronounced pattern
was found for ground communities. The high importance of habitat connectivity in shaping
high-mobility species community composition indicates that these green roof communities
are substantially connected by the frequent exchange of individuals among surrounding
green roofs. On the other hand, low-mobility species communities on green roofs are
more likely connected to ground sites than to other green roofs. The integration of
green roofs in urban spatial planning strategies has great potential to enable higher
connectivity among green spaces, so that eventually even communities of low-mobility
species become connected. Furthermore, improving the design of green roofs (composition
and configuration of vegetation and soil types) could enhance the ecological value,
particularly for low-mobility species.