Wageningen University & Research meet verrassende impact dakbloemenweide in eerste 37 dagen

Nadat eerder dit jaar het eerste onderzoek tussen Wageningen University & Research is aangekondigd, kan er inmiddels meer gezegd worden over de resultaten. Meer dan 40 inheemse soorten op het eigen substraat zijn voor 40 dagen gemonitord en de resultaten zijn verrassend goed! Zo waren er in de eerste maand al 80% van de tijd insecten waarneembaar, was de vegetatie al 7 cm hoog en had het dak ruim 1100 liter water kunnen opnemen. 

In de samenvatting schrijft WUR er het volgende over:

The green roof, which is extended for 12 m2, has the functions of supporting urban biodiversity and collecting rainwater. Firstly, biodiversity is promoted on various levels, considering both flora and fauna. More than 40 different native plant species are growing on the 8 cm substrate, creating a favourable habitat for the establishment of planted and spontaneous plants. Also, once the native plant community which is forming on the roof is established, it is going to act as a source of seeds which can disperse in the surroundings. Furthermore, even if the vegetation is still at its initial stages, it is already getting the attention of several insects, such as flies, hoverflies, bees, and wasps, which were observed during the 80% of the monitoring time. On the last monitoring date, the maximum height of the green cover was 7cm and the average 3.5 cm, so concerning mean values, the growing rate of the green cover was 0.95mm per day, roughly 1 mm per day. During 37 days, the green roof received 1275.2 litres of water and consumed 1127.2 litres to sustain itself, resulting in a consumption rate of 30.5 litres per day and roughly 2.5 litres per square meter per day. The excess water (148 litres) was drained into the water tank. Of the consumed water, 85% came from rainwater and 15% came from the tank. Due to the weather conditions in Amsterdam in this specific period (see Figures 1 and 2), characterised by high temperatures and high evapotranspiration rates, it was necessary to irrigate the green roof 6 times with 230 litres, 38.3 litres per irrigation (see Figure 3 for a summary of the results). Additionally, the rainwater catching surface connected to the water tank is larger than the green roof (micro-basins), which can increase the amount of rainwater which can be collected and stored in the water tank.