Climate
The local climate has to be considered in devising strategies for restoring rainforest. In our river valley, night frosts are common during winter. Cold air drains down from the surrounding hills and settles in the valley, making it a frost hollow, especially on nights that are clear of cloud. This effect (the “temperature inversion”) also condenses moisture as mist.
The local climate has to be considered in devising strategies for restoring rainforest. In our river valley, night frosts are common during winter. Cold air drains down from the surrounding hills and settles in the valley, making it a frost hollow, especially on nights that are clear of cloud. This effect (the “temperature inversion”) also condenses moisture as mist.
Even a mild frost (-1oC a metre or so above ground level) can kill the foliage of seedling rainforest species. Species such as lilly pilly (Acmena smithii), red ash (Alphitonia excelsa) and euodia (Melicope micrococca) benefit from the shelter of hardier natives, such as water gum and wattles, because they keep the frost off.
Even a mild frost (-1oC a metre or so above ground level) can kill the foliage of seedling rainforest species. Species such as lilly pilly (Acmena smithii), red ash (Alphitonia excelsa) and euodia (Melicope micrococca) benefit from the shelter of hardier natives, such as water gum and wattles, because they keep the frost off.
While any open grassy areas tend to be frosty, this changes once they have trees to keep the warmth in and the frost out. Trees contain a great deal of water and that water stores heat - it warms during the day then releases the warmth overnight. As well as that, the tree foliage slows down the cold air that streams down from the surrounding hills at night. The same foliage acts as a blanket by intercepting the radiation of heat from the ground to the cold night sky.
While any open grassy areas tend to be frosty, this changes once they have trees to keep the warmth in and the frost out. Trees contain a great deal of water and that water stores heat - it warms during the day then releases the warmth overnight. As well as that, the tree foliage slows down the cold air that streams down from the surrounding hills at night. The same foliage acts as a blanket by intercepting the radiation of heat from the ground to the cold night sky.
In the summer, the protective blanket of foliage has the reverse effect. The shade protects seedlings from being scorched by sunlight and provides them with a cooler and more humid environment. The overall effect is that rainforest seedlings regenerate much better under a protective tree canopy, even though they struggle to survive in the open. This is why we first established a protective canopy by planting “pioneer” species such as wattles in open areas.
In the summer, the protective blanket of foliage has the reverse effect. The shade protects seedlings from being scorched by sunlight and provides them with a cooler and more humid environment. The overall effect is that rainforest seedlings regenerate much better under a protective tree canopy, even though they struggle to survive in the open. This is why we first established a protective canopy by planting “pioneer” species such as wattles in open areas.
Frost on the leaves of a water gum Tristaniopsis laurina. This is one of the plants on our site that is most resistant to frost. Unfortunately for us, swamp wallabies love to browse on its seedlings, so we have to protect them with tree guards.