*3.3. Effect of Irrigation and Fertilization on Vegetation Cover and Biodiversity*

In 2011, on building 3, plots were marked to create fixed areas for annual irrigation and fertilization and to compare these areas with the normal situation without any extra treatments (see Table 1).

The test questions that were to be answered with this survey were:

In the vegetation analysis, the data were interpreted as follows. Specifically, these are the coverage values for the vascular plants, the total number of species, as well as the comparison of coverage values for all sedum species. The sedum coverage is an indicator of typical extensive green roofs. The coverage of all grasses together is an indicator for the shady parts of the north side and particularly the section of the roof shaded by the elevated part of building 3.

It was observed that the performance of sedum in general decreased after the first 10 years due to a lack of fertilization and irrigation. The number of plant species

decreased on all test plots. In the following dependent paired *t*-test procedures, only the observations for 2011–2020 are interpreted.

**Figure 7.** Aboveground annual harvested phytomass on the 30-cm boxes. Each of the three test plots represent 13 replicates at each date. The Op and Zi boxes are on building 2, and Op\_2 is on building 3. All data refer to dry matter.
