Trees are one of the oldest “citizens” of our Earth. They keep our air clean， reduce noise pollution， improve water quality and provide food and building materials.

Just like us， trees change a lot as they grow. At 1 to 3 years old， young trees learn how to protect themselves. For example， many trees grow thorns to warn animals not to go near. Most young trees have large， deep green leaves so that they can catch enough sunlight and change it into their food and energy.

When trees are 4 years old， they begin to grow very rapidly and become strong enough to face challenges later in life. At the age of 15， trees become young adults. They grow more slowly and begin to produce flowers and fruit.

It is not until the tree is 20 to 25 years old that it becomes a real adult. The tree reaches its largest size. ?The adult tree gives us shade， oxygen and natural beauty; it is also a great place for a tree house， or a place for us to read a book， listen to music and so on. If we give the adult tree proper care， it will go on to live healthily for many years.

Gradually， trees begin to grow older and older and even die. At this time， they still have their important place in nature. When a tree becomes hollow or part of it becomes dead， it provides a home to small animals and is a source of food for many other animals.

In many ways， the life of a tree is similar to our own life experience. When we are looking at the life of a tree， we learn about that each period of life brings its own form of joy and challenge.

Enjoy every minute of the life of the trees and take care of the trees！

樹是地球上最古老的“居民”之一。它們能凈化空氣，減少噪音污染，提高水質(zhì)，以及提供食物和建筑材料。

就像我們?nèi)祟愐粯樱瑯湓谏L(zhǎng)過程中也會(huì)發(fā)生很多變化。1—3歲時(shí)，小樹們會(huì)學(xué)習(xí)如何保護(hù)自己。比如，許多樹會(huì)長(zhǎng)出刺，以此來警告動(dòng)物不要靠近它們。大多數(shù)小樹長(zhǎng)著大大的深綠色的葉子，這樣它們就可以吸收足夠的陽(yáng)光并轉(zhuǎn)化為自己所需的食物和能量。

當(dāng)小樹長(zhǎng)到4歲時(shí)，它們會(huì)進(jìn)入快速生長(zhǎng)階段，樹干變得更加堅(jiān)固，足以抵御未來可能面臨的危險(xiǎn)。到15歲時(shí)，樹就“成年”了。這時(shí)它們的生長(zhǎng)放緩，開始開花結(jié)果。

不過，到20—25歲時(shí)，樹才算真正地長(zhǎng)大，長(zhǎng)成一棵棵參天大樹，為我們提供蔭涼、氧氣和宜人的自然風(fēng)光。這時(shí)候的樹可以做成樹屋，也是我們進(jìn)行閱讀、聽音樂等的好去處。如果我們給予妥善照料，它們會(huì)健康生長(zhǎng)很多年。

慢慢地，樹開始逐漸變老，有的甚至?xí)八馈比ァ＿@時(shí)候，它們?cè)谧匀唤缰腥匀话l(fā)揮著重要作用。當(dāng)樹內(nèi)部空心或部分已經(jīng)枯萎時(shí)，它們便成了小動(dòng)物的棲息地，也是許多其他動(dòng)物的食物來源。

在許多方面，樹的一生都和我們?nèi)祟愊嗨?。?dāng)我們觀察樹的一生時(shí)，我們了解到人生的每個(gè)階段都會(huì)帶來不同的歡樂和挑戰(zhàn)。

讓我們珍視樹的生命，保護(hù)樹木！

Vocabulary

reduce v. 減少，縮小

thorn n. 刺，棘刺

hollow adj. 中空的;空心的

source n. 來源;出處