tropical

They discussed a plan to preserve the world's tropical forests.

Doctors back home may be unfamiliar with the symptoms of tropical diseases.

And our first stop is tropical snack island.

Many are found in tropical and subtropical areas of the world, where accumulation of high concentrations of metals may afford some protection against plant-eating insects and microbial pathogens.

I mean, you wouldn’t call it a tropical paradise or anything, uh…or maybe you would if you think about how today in some parts of the Sahara it…it only rains about once a century.

Proxy temperature records have been reconstructed from ice core drilled out of the central Greenland ice cap, calcite shells embedded in layered lake sediments in Western Europe, ocean floor sediment cores from the tropical Atlantic Ocean, ice cores from Peruvian glaciers, and ice cores from eastern Antarctica.

If one focuses on the wet months, one calls the Maya homeland a "seasonal tropical forest"; if one focuses on the dry months, one could instead describe it as a "seasonal desert."  

But the Maya homeland lies more than sixteen hundred kilometers from the equator, at latitudes 17 to 22 degrees north, in a habitat termed a "seasonal tropical forest."  

Properly speaking, tropical rainforests grow in high-rainfall equatorial areas that remain wet or humid all year round.

To understand the ancient Mayan people who lived in the area that is today southern Mexico and Central America and the ecological difficulties they faced,one must first consider their environment, which we think of as "jungle" or "tropical rainforest."  

We’ve gone over where coral reefs are usually formed – along the edges of shallow ocean banks in tropical or subtropical regions, and the fact that they are declining at an alarming rate.

They concentrated their studies on a thirteen-hectare tract of tropical dry forest that contained numerous nests of nine species of stingless bees.

Stingless bees are abundant in tropical and subtropical environments, where they gather nectar and pollen from a wide variety of flowers.

They studied competition and nest spacing in populations of stingless bees in tropical dry forests in Costa Rica.

I mean, think of…say, tropical or temperate marine environments, which have incredibly diverse fish populations.

Structure is essentially the architecture of vegetation, and as in the case of tropical forests, it can be extremely complicated. 

This leads to a complex structure in the layers of plant material In a tropical rain forest, for example, a very large quantity of plant material builds up above the surface of the ground.

In time, this organization became a state, and knowledge of its functioning was exportable, as were pottery, tropical bird feathers, specialized stone materials, and other local commodities.

It is interesting that temperate seagrass beds accumulate sediments from sources outside the beds, whereas tropical seagrass beds derive most of their sediments from within.

Indeed, they have been called the marine version of the tropical rain forest, rivaling their terrestrial counterparts in both richness of species and biological productivity.

They do best when the relative humidity in their nest is above 96 percent and the temperature is fairly high, an optimum of about 79°F for temperate zone species and about 86°F for tropical species.

The Saharan herders who moved southward to escape drought were almost certainly also cultivating sorghum, millet; and other tropical rainfall crops.

Also, cycads (a type of tropical plant that resembles a palm tree) produce special aboveground roots that harbor nitrogen-fixing cyanobacteria.

Evidence for this conclusion is that nutrient systems are more open in the richest tropical soils and tightest in the poorest soils.

Closed nutrient systems have evolved in response to the leaching effects of heavy tropical rainfall.

Consequently, tropical rain forests typically have what are known as closed nutrient systems, in which minerals are handed off from one organism to another with little leaking through to the soil.

Many tropical rain forest plants (like those in other forests) have mycorrhizal (fungus-root) partners whose delicate hyphae spread through great volumes of soil, from which they release and absorb minerals and ferry them back to the host plant in exchange for needed organic compounds.

In contrast to grasslands, where a large proportion of plant biomass is produced underground, that of tropical forests is nearly all aboveground.

Given such poor soils, how can lush tropical forests exist?

Because the concentration of dark-colored organic materials is low in tropical soils, they are often colored red or yellow by the presence of iron, aluminum: and manganese oxides; when dry, these soils become rock hard.

Because organic compounds help loosen compact clay soils, hold water, and bind mineral nutrients, the relative lack of organic materials in tropical soils is deleterious to plants.

High moisture and temperatures speed the growth of soil microbes that decompose organic compounds, so tropical soils typically contain far lower amounts of organic materials (humus) than do other forest or grassland soils.

Aluminum is the dominant cation (positively charged ion) present in tropical soils; but plants do not require this element, and it is moderately toxic to a wide range of plants.

Tropical forest soils also often contain particular types of clays that, unlike the mineral-binding clays of temperate forest soils, do not bind mineral ions well.

Because of rain leaching, most tropical rain forest soils have low to very low mineral nutrient content, in dramatic contrast to mineral-rich grassland soils.

On viewing the lush plant growth of a tropical rain forest, most people would conclude that the soil beneath it is rich in nutrients.