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Plants in the Deserts
沙漠中的植物
Some cacti, like the saguaro, grow to tree size, but true trees need more moisture than most desert environments can supply, so they are scarce on deserts.
一些仙人掌，如撒瓜羅，能長到橡樹那么高。但真正的樹卻需要比大多數沙漠所能提供的更多的水分，所以樹在沙漠里是鮮見的。
Close to streambeds, cottonwoods can sometimes be found. Though these streams are dry most of the year, water flows there longest and is usually available fairly close to the surface. Elsewhere, trees must send taproots deep into the hard baked desert soil to draw on underground water. Perhaps the most widespread family of trees on the world's deserts is the acacia, whose taproots drill down as fas as 25 feet (7.5 meters).
在小溪河床附近，有時能發現三角葉楊。盡管一年的大多數時間里這些小溪都是干涸的，那里卻是水流的時間最長的地方而且水分相當靠近地表。其他地方樹木的主根必須深入受炙烤而堅硬的沙漠底部的土壤以吸取地下水。在沙漠里分布最廣的樹或許是刺魏，其主根能深達25英尺（合75米）。
The mesquite common on North American deserts in both tree and shrub forms, does not begin to grow above ground until its root system is completely developed, ensuring the plant a supply of moisture. The roots of shrubs and trees help to hold the desert soil in place. Their stalks and branches also act as screens to keep the wind from sweeping great drifts of sand along the surface. These services are vital if a desert is to support life.
牧豆樹屬植物不論是喬木和灌木，在北美沙漠中經常可見，在它根部系統完全生長發達到能保證提供充足的水分時才長出地面。灌木和樹的根有助于固定沙漠中的土壤，它們的莖和樹枝同時起屏障的作用，防止風從沙漠表面吹起大堆的沙。如果沙漠要支持生命，這種作用必不可少。
In addition to a few varieties of trees and tough shrubs, most deserts have grasses, herbs, and other annual plants. These do not compete for moisture with the longer lived growth. They spring up quickly after rains, when the surface is moist. Then, for a brief time, the desert can be literally carpeted with color. Almost as quickly as they appeared, these small plants die away. But they have developed special ways of ensuring the life of another generation when rains come again.
除了一些種類的樹木和頑強的灌木外，大多數沙漠里還有青草、草本植物和其他年生植物。它們并不與長期生長的樹木競爭水分。當雨后地表還潮濕時它們就迅速發芽，然后在一個短時間里，給沙漠鋪上綠色地毯。這些小植物很快就消失了，幾乎就像它們長出來時那樣迅速，但它們已發展了特殊方式來保證在下次降雨來時下一代的生命。
