Tropical Rainforests
The steamy atmosphere, constant sunlight, endless rains and high temperatures year-round spell life for the forest flora. The fast nutrient turnover also helps promote favorable growth conditions and allow them to evolve into a multitude of different species. The foliage can be so dense that you cannot move without a machete, but since only about 10 percent of the total sunlight manages to penetrate through the forest canopy, the undergrowth is generally sparse, and the forest floor can be surprisingly open and easy to move around in.
High in the canopy where the sun comes and goes, the moisture that is built up has a chance to be blown away and the temperature between night and day can change as much as 15 degrees. Down below, the air is stagnant, loaded with moisture, and to the visitor it may seem constantly humid, but this is only true near the ground. Within 30 vertical meters there are two different climates.
Plunging deep into the forest, it becomes apparent to visitors how much variety there is. Distinct species of flora congregate into plant "neighborhoods" with few other species interspersed. In the rainforest you might pass one example of a particular tree species and then not see it for another half a mile. In between, however, there may be hundreds of other species.
The forest floor is like a decomposition factory where bacteria, mold, and insects work nonstop, degrading the constant littering of leaves and fruits into nutrient molecules. A leaf from a North American oak that has fallen may take a year to decompose, however, within the tropical rainforest it would fully decay within a month. These precious nutrients and minerals must be returned to the canopy to start the cycle of life again or they will be washed away by the daily drenching of rain. Trees accomplish this by using a thick mat of rootlets that grow close to the surface of the inordinately thin soil.
The competition for light and space has promoted the evolution of long, slender, branchless trunks, some of which are well over 35 meters tall. High up in this vaulted canopy is where more than 90% the jungles photosynthesis takes place. Above this dense carpet of greenery rise a few scattered giants towering to heights of 70 meters or more.
The dark nave of the rainforest cathedral is rich mix of ferns, saplings, and herbaceous plants, seeping in moisture. There are clinging vines everywhere in the jungle fighting for a chance to get in the sun. Instead of using up the energy to build their own supports, these vines and lianas clutch to the straight, limbless trunks of a typical rainforest tree species to provide the support they need to reach the sunlight. As they snake their way through the treetops, sometimes reaching lengths of up to 300 meters, they spiral around their host like corkscrew or they cement themselves to a tree with three-pronged tendrils.
The scaffolding of massive boughs is colonized at all levels by a riot of bromeliads, ferns, and other epiphytes (plants that take root on plants but that are not parasitic). Tiny spores sprout on the bark, gain a foothold, and spread like luxuriant carpets. As they die and decay, they form compost on the branch capable of supporting larger plants that feed on the leaf mold and draw moisture by dangling their roots into the humid air. Soon every available surface is a great hanging gallery of giant Elkhorn and ferns, often reaching such weights that whole tree limbs are torn away and crash down to join the decaying litter on the forest floor.
The canopy is home to legions of monkeys, sloths, and other fruit and leaf eating mammals. There are larger hunters that live up there too. The tree dwelling cats up there are very capable of catching monkeys and squirrels. The snakes that slither along the canopy are not the monsters you would initially think of, but smaller creatures, some twig-thin which feed on frogs, lizards and nesting birds.
As the day fades out and the evening begins, the noise in the forest becomes almost silent for a moment. Slowly, the buzz of the insects begins, the rodents come out to begin their foraging, and the fruit bats replace the birds. Then the hunters come out to join them all in the moist velvet blanket of the tropical night.
