Investigating Earth's Desert, Grassland, and Rainforest Biomes
INVESTIGATING EARTH's DESERT GRASSLAND AND RAINFOREST BIOMES gigantea while the cooler Mojave Desert is home to the Joshua tree Yucca brevifolia Deserts are home to reptiles marsupials and mammals Perhaps the camel is the iconic desert animal well suited to the climate with its ability to travel many miles without water People also inhabit deserts and even grow crops there though only in areas known as oases where water is available Grasslands occupy another 20 percent of Earth's land These grass dominated areas extend between forests and deserts The grasses vary as soil and climate conditions change For example more arid areas closer to deserts grow short or bunch grasses Tropical grasslands called savannas have a marked dry season and yield coarse stiff grasses In the middle latitudes or prairies temperatures are less extreme and taller grasses grow alongside flowering plants in the fertile soil Steppe grasses tend to be rather short with shallow root systems making for a less varied landscape Many animals inhabit savannas such as herbivorous plant eating animals which in turn attract carnivores or meat eaters Tropical grasslands teem with zebras lions and kangaroos More temperate grasslands are home to hawks horses and prairie dogs
INTRODUCTION The verdant rainforest features broad leaved evergreen trees and abundant rainfall In many areas the upper layer of trees creates a canopy so thick that sunlight rarely shines through to lower foliage An incredible diversity of plants and animals is found in rainforests such as orchids lia nas orangutans bats birds of paradise and many frog species Although some rainforests occur in more temperate areas most are found in warm trop ical climes around the equator Subtropical rainforests lie beyond the equatorial region temperatures in these forests generally only fluctuate a little though rainfall may be unevenly distributed Montane and tropical seasonal rainforests diverge some from the classical definition of rainforest but they do have periods of intense rain and moisture Deserts grasslands and rainforests cer tainly cover an ample portion of the globe On the following pages you will find a sweep ing look at these captivating areas each with its own distinctive flora and fauna
CHAPTER 1 THE DESERT ENVIRONMENT A biome is a large region of Earth that has a certain climate and certain types of living things Occupying some 20 percent of the Earth's surface des erts are one of the planet's major types of biomes Any barren region that supports very little life may be called a desert More com monly however the term desert is reserved for regions that are barren because they are arid or dry Arid deserts receive little precipitation and are characterized by specialized plants that tolerate drought conditions and salty soils Deserts may or may not be hot Land features range from windswept expanses of loose sand to rugged mountains bare rock and plateaus strewn with gravel and boulders CLIMATE Deserts are areas in which there is a shortage of moisture available for plants There is no precise measure of how dry such an area must be to be called a desert Characteristically
THE DESERT ENVIRONMENT deserts receive an average of less than 10 inches 25 centimeters of rain or other pre cipitation per year Many deserts get less than half that amount of rain yearly and some receive almost none Regions with an average annual precipitation between some io and 16 inches 25 and 40 centimeters are often called semideserts But rainfall is not the only factor that influences how much water is available to sup port plants The distribution of the rainfall throughout the year the humidity of the air Desert rainfall is sparse and sporadic so some species of cactus lack leaves which means there is less surface area from which they can lose water iStockphoto Thinkstock
