school energy&environment

A thick forest

The foliages of trees are very close to each other and form a very thick canopy.
Only approximately 1% of the light that gets to the canopy reaches the ground and so the lower branches are too dark to let leaves develop and there’s virtually no undergrowth. In particular, there are very few herbaceous species.
Moving up from 1 to 20 m above ground, we still find a moderate light (approximately 5%), high humidity and no wind at all. This means there are very few plants with anemogamous pollination, which means pollinated by the wind. Flowers have very bright colours and a strong scent to attract insects, winds or bats for pollination. Many plants have caulifloria, which means “flowers on the caulis” or stalk. In this case, flowers sprout straight from the naked stalk and not from the leaves, so that they are more conspicuous. An example of this particular phenomenon is the cocoa tree, whose flowers, stuck to the stalk, turn into big fruits, which are picked by the monkeys and rodents and eaten far off. In this ecosystem, leaves are generally large and oval, but in most cases they have a down-turned tip at the end, called drip-tip, to let rainwater flow down. Prolonged exposure to humidity is actually harmful for the leaves, since it promotes the growth of epiphylla (generally mosses, lichens, algae and mildews growing on the leaf surface).
Most of the plants of this ecosystem are approximately 30-40 m tall (as tall as a 12-storey building). The stalk of these plants is as straight as a pillar up to 20 m, then suddenly branches off into a crown of leaves. The leaves on the canopy are in full light, with not too much humidity and some wind: these leaves are therefore quite small and do not have down-turned tips.