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ecosystems

The forest has its own seasons

Even if the temperature of this ecosystem is stable all through the year, the trees change their leaves at particular intervals: some species change them every 6 months, others every 13 months and others at different times. All leaves are renewed at the same time to defend themselves from herbivores, since this temporarily creates plenty of soft food, followed by many months when the leaves become hard and uneatable. If the leaves were renewed one at a time during the year, they would all be eaten by the herbivores.

“Big bang” of flowers

Often flowers also bloom all together, making a spectacular aesthetic impact called the “big bang” (e.g. the Tapirira guaianensis in Amazonia). This strategy ensures some flowers, fruits and seeds to resist the plunder of insects, birds and mammals.

A flower at a time
A different strategy is the so-called “steady state” adopted by the plants of genus Gurania in Amazonia, which only produce one or two flowers a day to let its pollinators (generally solitary bees) locate the plant and find some available flowers.

Giant trees
Extremely tall trees, sometimes exceeding 60 m, stand above the forest canopy. Some of the tallest ones are the Dinzia excelsa in South-America, the Entandrophragma cylindricum in Africa and the Koompassia excelsa in the south-east of Asia.
Most of these trees have shallow roots because the ground is very thin here, due to the humidity that promotes a fast decomposition, so during storms a large tree may often fall to the ground and drag other plants along. This gives rise to a small clearing, which is quickly colonised by heliophilous plants (i.e. plants that love sun-exposed areas) which immediately germinate. Such clearings can be often found in tropical forests and this is why this is an uneven biome.

With the sponsorship of the Italian Ministry of Education, Universities and Research
 
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