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The Lowland Tropical Rainforest

Part of what goes into making a forest a tropical rainforest is the climate, which is very warm and very humid but not necessarily very hot. In the tropics, daylengths are more-or-less the same throughout the year, so there are no opportunities for heat to build up or be lost; therefore, you have more-or-less consistent temperatures throughout the year. What differs throughout the year is the rainfall: there is a marked rainy and dry season. Tropical rainforests generally receive at least 80 inches of rain per year.

So what is it that is so appealing about the warm and humid tropical rainforest?

For me, there's something about the ecologic complexity, the incredible biodiversity, the interdependency of the plants and animals, and the quietly dynamic personality of the rainforest. And then there's the enveloping exoticness, otherworldliness, and the captivating lushness that closes you off from the rest of the world.


This "lushness" however is somewhat deceiving. As I had read in Tropical Nature (Forsyth and Miyata) - the book I had brought along on the first trip and reread on the second - the Europeans who came and prospected for farmland in the lowland tropical rainforests found that despite this seeming lushness, the soils were in fact weak. The prospectors cut down trees and planted their crops, but nothing grew. It turns out that only a tiny amount of nutrients ever penetrate more than an inch or two into the soil. The majority of the nutrients are tied up in the trees.

But then one thinks, how can such a weak soil support the towering trees found in a rainforest? The answer is in the fungi of the forest floor that forms a symbiotic relationship with the roots of the plants, referred to as mycorrhizae. And you'll notice that the trees are often buttressed, spread out more horizontally across the ground than vertically into the ground.

The fungi of the forest floor are great at recycling potassium and phosphorus - two of the three main nutrients a plant needs to survive - and the third, nitrogen, is taken from the rain. Nutrient-rich animal waste also plays a big part in this nutrient-scarce environment, and there are many interesting accounts of this in the Tropical Nature chapter "Fertility".

It's mentioned in Tropical Nature that "common species are rare and rare species are common." Upon first glance, some of the trees might look the same, but if you observed them from the canopy, you'd discover that they are in fact different species. Another example is that you'll see one species of poison dart frog, then you'll see another species of poison dart frog, then another, but never the same species in a given area. It's an intricate, interdependent system - some species of animals only feeding on one species of plant!

Scientists believe that this narrow specialization, along with the tropical rainforest's stable climate, is what creates such astounding biodiversity. A mere 7% of the world is rainforest, yet 50% of the world's plant and animal species inhabit the rainforest!


That being said, in such an interdependent system, just as the climbing vines intertwine among the other flora in the rainforest, so do all the organisms in the rainforest, and damaging one affects the others.

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