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Colombia hue because of Colombia’s natural vegetation, which is mainly tropical ­rainforest. Natural vegetation, or flora, depends primarily on two important elements of the physical environment: climate and soil. Sunlight, temperature, and precipitation establish the natural limits of growth for various plants. As a result, each climate type tends to have just one or two dominant plant com-­ munities. Climate is also very important to soil development. It affects the rate of rock weathering (decomposition or disin-­ tegration into fine particles), overlying vegetation, erosion, and leaching (the removal of soil nutrients by water). Soil is vital to plants because it can limit the nutrients and water that plants need in order to grow. Nutrients come from the tiny particles of clay, silt, and sand that comprise the soil, as well as from organic matter, or decaying plant and animal tissue. Soil also stores water that plants need to survive. A soil’s depth and texture (or particle size) affect the amount of mois-­ ture and food in the soil. For example, tropical rainforests have deep soils, abundant moisture, and plentiful organic matter on the surface. In contrast, desert soils are thin and hold only small amounts of organic matter and soil ­moisture. Tropical rainforests thrive in the low, hot, wet tierra caliente zone. The forest’s thick canopy of leaves and vines protects the deep soil from tropical heat and heavy rains. Unfortunately, Colombians have cleared away large areas of the lush forest and exposed the soil to water erosion and baking rays of the sun. As a result, Colombians are no longer able to grow crops, harvest timber, or even collect firewood in such areas. Geographers call the still forested area of this region the “Zone of Tropical Prod-­ ucts” because carefully managed crops of cassavas (an edible root plant, also called manioc), sugarcane, bananas, and other ­water-­demanding and ­ warmth-­loving plants can grow well there. Even so, forest clearing and soil erosion are serious prob-­ lems. Some sizeable areas of the tropical rainforest still exist in


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