托福阅读tpo32.doc

托福阅读 TPO32 查看托福口语 TPO1-3 4 文本+MP3 ,请点击: 托福 TPO 口语大全查看托福阅读 TPO1-33 阅读原文+ 题目+ 答案,请点击: 托福 TPO 阅读大全查看托福听力 TPO 1- 30 原文+ 题目+MP3 音频下载,请点击: 托福 TPO 听力大全查看托福写作 TPO1-25 文本大全,请点击: 托福 TPO 写作大全托福阅读 TPO32 第1篇:Plant Colonization Colonization is one way in which plants canchange the ecology ofa site. Colonization is aprocess with ponents: invasion andsurvival. The rate at which a site is colonized byplants depends on both the rate at which anisms (seeds, spores, immature or mature individuals) arrive at the site and their essat ing established and surviving. ess in colonization depends toa great extent onthere being a site available for colonization —a safe site where disturbance by fire or bycutting down of trees has either peting species or reduced levels petitionand other negative interactions toa level at which the invading species can eestablished. For a given rate of invasion, colonization ofa moist, fertile site is likely to bemuch more rapid than that ofa dry, infertile site because of poor survival on the latter. Afertile, plowed field is rapidly invaded bya large variety of weeds, whereas a neighboringconstruction site from which the soil has pacted or removed to expose a coarse,infertile parent material may remain virtually free of vegetation for many months or even yearsdespite receiving the same input of seeds as the plowed field. 殖民化是植物能够改变一个地方生态的一种方法。这是一个由两部分组成的过程:入侵和生存。一个地方被植物殖民的比率是取决于两个东西的速率:生物体( 种子,孢子,成熟或不成熟的个体) 到达这个区域和它们能成功地立足和生存。成功的殖民化取决于有一个非常适合定居的场所——所谓安全的地方就是,火灾和砍伐的干扰已经赶走了竞争物种或已经减小了竞争力和对入侵物种要立足产生的阻力。对于入侵速率, 迁居到一个潮湿肥沃的地方会比到一个干的, 不肥沃的地方更快, 因为在后者更难存活。一个肥沃, 翻耕的领域会迅速地被大量多样的野草侵入, 然而一个邻近的建筑区, 为了曝光一个粗糙不肥沃的, 并且几乎可能是多月或多年都没有植被覆盖的母质层, 它的土壤已经是被压实或是移动, 尽管是收到了如在翻耕区域相同的种子投入。 Both the rate of invasion and the rate of extinction vary greatly among different plantspecies. Pioneer species — those that occur only in the earliest stages of colonization — tend tohave high rates of invasion because they produce very large numbers of reproductivepropagules (seeds, spores, and so on)