Cultivation principle

Commentary

Relationship between substrate depth and fertility and plant abundance

This relationship was pointed out by [90] and [109] but may not apply to the ESBS since lush vegetation can exist on infertile and thin sands. Nevertheless, the key should be to match conditions on the GR closely with those enjoyed by the natural community, a factor likely to be critical to success [31] [138] and [120] .

Test ground level soil mantle before installation on the GR

The principle of matching substrate depth and characteristics, noted immediately above, should also be applied to the soil micro-organisms and fungal populations of the ESBS Aeolian sand mantle to ensure representative communities are included in the GR substrate [124] .

Test landscape materials for toxins

Landscape materials should be checked for toxins (see Installation Protocol below and Table 3).

Fine landscaping details

Employ features on the GR found at grade such as rocks and tree branches to provide suitable microclimates as well as shade and sunny areas to encourage plant (and faunal) diversity [60] . Features like tree branches may need to be fabricated from lightweight materials to minimise roof loads and large rocks will need to be avoided.

Substrate depths

Vary substrate depths in order to assess the ESBS community’s response to this variable.

Maximise ecosystem services

The planting design should attempt to increase the functional diversity of species to amplify ecosystem output, while being aware of GR limitations regarding substrate depth.

Irrigation

One researcher’s findings [138] regarding improved plant survival with supplementary watering do not apply to Sydney’s rainfall or the drought-adapted nature of the ESBS. However, one test cell may be irrigated for experimentation purposes.

Select plant species

Select plant species to reflect concerns about the lack of fire regimes, species which have difficulty forming soil seed banks and those plants which are no longer present on remnant sites. Selection to be conducted in association with Randwick Community Nursery and the School of Biological, Earth and Environmental Sciences at UNSW. There is an overarching limit on substrate depth and plant height dictated by the roof load-bearing capacity.

Cultivation guidelines

Prepare cultivation guidelines including the need for hand weeding and for collecting and germinating seed to test the viability of green roofs as seed orchards.

Implementation and outcomes

Tracking progress in achieving objectives will require a detailed monitoring plan (see Section 5.4 below).