Data from: Norway and Sweden Green Roof (GF) plant data

Standard succulent vegetation mixes developed mostly in temperate climates
are being increasingly used on green roofs in different climate zones with
uncertain outcome regarding vegetation survival and cover. We investigated
vegetation on green roofs at nine temperate, cold and/or wet locations in
Norway and Sweden covering wide ranges of latitude, mean annual
temperature, annual precipitation, frequencies of freeze-thaw cycles and
longest annual dry period. The vegetation on the roofs were surveyed in
two consecutive years, and weather data were compiled from meteorological
databases. At all sites we detected a significant decline in species
compared to originally intended (planted/sown) species. Both the survival
rate and cover of the intended vegetation were positively related to the
mean annual temperature. Contrary to a hypothesis, we found that intended
vegetation cover was negatively rather than positively related to mean
annual precipitation. Conversely, the unintended (spontaneous) vegetation
was favoured by high mean annual precipitation, and low mean annual
temperature, possibly by enabling it to colonise bare patches and
outcompete the intended vegetation. When there is high mortality and
variation in cover of the intended vegetation, predicting the strength of
ecosystem services the vegetation provides on green roofs is difficult.
The results highlight the needs for further investigation on species
traits and the local factors driving extinction and colonisations in order
to improve survivability and ensure a dense vegetation throughout the
successional stages of a green roof.