Australian native biodiversity for a Green Roof is possible

Over the past 3 years I have been studying Coastal Sandstone Plateau Rock Plate Heath for its resilience. I am particularly interested in the way plants grow on shallow soils around Sydney in this vegetation type. There is a wide variety of diversity in both flora an fauna in this heath. There are some special plant adaptions and symbiotic relationships that make these plants thrive in harsh conditions. Wherever plants grow there is a rich abundance of lichens, mosses and insects above the ground. The symbiotic relationships ensure moisture is retained and nutrients provided to sustain a growth. Below the ground fungal mycorrhizal associations are related to nutrient exchange with fungus benefiting from sugars created by plants photosynthesis. The plants benefit from the nutrients available from the huge surface area that fungal hyphae provide. When plants are under extreme stress, after a few months without rain some take a deep red colour in their foliage. This could be a defence mechanism which is often associated in red leaves and toxic compounds.  Apart from field research my experiments included growing these plants in green roof modules over a 3 year period.  I observed how species persist and thrive. On the ridge tops around Berowra plants will grow in 15mm of soil and are possibly decades old. I grew plants in trays 45mm deep with great results. Plants were grown from collected seed and cuttings, I included lichens and site soil to include fungus. It is my hope that emulating this vegetation type on our buildings that biodiversity, particularly birds will have their habitat enhanced in our urban environment.

There are many species, some include Leptospermum arachnoides, Calytrix tetragona, Gahnia aspera, Patersonia sericea and my favourite Micromyrtus blakelyi.

Green roof plant Baeckea brevifolia turning red in a dry summer period. 

Green roof plant Baeckea brevifolia turning red in a dry summer period. 

Green roof plants here is Baeckea and Casuarina nana growing in a mere 45mm depth of growing media for over 3 years in the same tray.

Green roof plants here is Baeckea and Casuarina nana growing in a mere 45mm depth of growing media for over 3 years in the same tray.

Trees led us to ourselves

We wrote philosophies, built faiths and took every kind of comfort from trees. They gave language to our existence as we put down roots, stretched our limbs, budded in infancy and were felled in old age. They were mute companions to our lives and worshipped beyond themselves as the better part of balance and aspiration. They offered steadiness and long patience even as we failed in those. They were meeting points and sites of rough justice. They gave the idea and supplied the material for shelter. They offered an image of completion, which was an illusion, but enough. Theirs was a whisper in the wind to the human ear both tragic and hopeful. Civilisation grew from exploiting, destroying, venerating and looking back on them. Trees led us to ourselves and we stood against them, trunk to trunk, arms upon branches, our thoughts tangled in the stars.

from: The Tree in Changing Light by Roger MacDonald (Random House, Sydney, 2001, pp. 153-169)

Ghaf tree Prosopis cineraria, Evolvement expedition to the UAE.

Ghaf tree Prosopis cineraria, Evolvement expedition to the UAE.

Take this Ghaf tree (Prosopis cineraria) I found on a journey in the UAE. It survives in the fiercest climate with roots down 30 metres indicating water. Providing relief for people and camels alike.