Timberline Vegetation on Mountains

1、Timberline Vegetation on Mountains The transition from forest to treeless tundra冻土苔原 on a mountain slope斜坡 is often a dramatic one. Within a vertical垂直 distance of just a few tens of meters, trees disappear as a life-form生物形式 and are replaced by low shrubs灌木, herbs牧草药草, and grasses. This rapid急速的 zo

2、ne of transition is called the upper timberline树带界限or tree line. In many semiarid半干旱 areas there is also a lower timberline where the forest passes into逐渐变成 steppe干草原 or desert at its lower edge, usually because of a lack of moisture.水分降雨量 在山斜坡上，森林到树木稀少的冻土苔原的转变通常是很戏剧化的。在垂直只有几十米的距离，树木像生物一样消失被低矮的灌木、草药

3、和草代替。这种急速转换的区域叫做上行树带界限或者林木线。在很多半干的地区通常由于缺少水分也会有下行树带界限，森林在更低的边界变成干草原或者沙漠。 The upper timberline, like the snow line, is highest in the tropic热带 and lowest in the polar极地 regions. It ranges from sea level in the polar regions 极地to 4,500 meters in the dry subtropics亚热带 and 3,500 4,500 meters in the mois

4、t潮湿的 tropics热带. Timberline trees are normally evergreens, suggesting that these have some advantage over deciduous落叶 trees (those that lose their leaves) in the extreme environments of the upper timberline. There are some areas, however, where broadleaf deciduous trees form the timberline. Species o

5、f birch桦木, for example, may occur at the timberline in parts of the Himalayas. 上行树带界限，就像降雪线，在热带是最高的而在极地是最低的。它的高度从极地的海岸线到干旱的亚热带4500米和湿热带的3500-4500米。树带界限的树一般来说是常绿的，假设他们相对落叶树（那些没有树叶的）在上行树带界限的极度环境中更具优势。但是在某些地方存活着树带界限的阔叶落叶树。举个例子，桦木的几种可能出现在喜马拉雅的部分树带界限。At the upper timberline the trees begin to become twis

6、ted扭曲 and deformed变形. This is particularly true for trees in the middle and upper latitudes, which tend to attain greater heights on ridges山脊, whereas in the tropics热带 the trees reach their greater heights in the valleys. This is because middle- and upper-latitude纬度 timberlines are strongly influenc

7、ed by the duration持续时间 and depth of the snow cover. As the snow is deeper and lasts longer in the valleys, trees tend to attain greater heights on the ridges山脊, even though they are more exposed to high-velocity速度 winds and poor, thin soils土壤 there. In the tropics热带, the valleys appear to be more fa

8、vorable because they are less prone易于，倾向的 to dry out, they have less frost霜冻, and they have deeper soils. 在上行树带界限，树木开始扭曲和变形。尤其是中高纬度的树，趋向于在山脊上长得更高，然而在热带，山谷的树才会长得更高。这是因为中高纬度的树带界限受降雪持续时间和深度的强烈影响。由于在山谷雪更深降雪时间更长，树木趋向于在山脊上长得更高，尽管他们更加暴露于高速强风和稀薄的土壤。在热带，山谷更有利于生长，因为干旱更低的可能性，那里有更少的霜冻和更深的土壤。 There is still no u

9、niversally普遍的 agreed-on explanation for why there should be such a dramatic cessation终止 of tree growth at the upper timberline. Various environmental factors may play a role. Too much snow, for example, can smother焖住窒息 trees, and avalanches雪崩 and snow creep蔓延移动 can damage or destroy them. Late-lying

10、经久不化 snow reduces the effective growing season to the point where seedlings树苗 cannot establish themselves. Wind velocity速度 also increases with altitude海拔 and may cause serious stress for trees, as is made evident by the deformed畸形 shapes at high altitudes. Some scientists have proposed提出 that the pr

11、esence存在 of increasing levels of ultraviolet极强紫外线 light with elevation海拔 may play a role, while browsing啃牧放养 and grazing animals like the ibex野山羊 may be another contributing factor. Probably the most important environmental factor is temperature, for if the growing season is too short and temperatur

12、es are too low, tree shoots嫩干 and buds蓓蕾，树芽 cannot mature sufficiently充足的 to survive the winter months. 现在对于为什么在上行树带界限会有如此戏剧的树木增长量的终止仍还没有广泛被认可的解释。多种环境因素可能产生影响。比如过多的雪可能焖住树窒息和雪崩和雪的蔓延可能破获或者摧毁树木。经久不化的雪减少了有效生长季节的时间以至于树苗不能生长。风速也会伴随高度而增加从而可能给树木造成重压，这也被高海拔的变形的树木而证实。一些科学家已经提出伴随纬度增加而增加的紫外线密度也可能产生影响，食草动物比如野山羊可

13、能也是另一个影响因素。可能最重要的环境因素是温度，因为如果生长季节过短，温度过低，树木的嫩枝和蓓蕾不能充分成熟地在冬天存活。 Above the tree line there is zone that is generally called alpine高山 tundra冻土苔原. ¢ Immediately adjacent毗邻 to the timberline, the tundra consists of a fairly complete cover of low-lying shrubs灌木, herbs药草, and grasses, while higher up

14、the number and diversity多样性 of species decrease until there is much bare裸露的 ground with occasional零星的，偶然的 mosses苔藓 and lichens地衣 and some prostrate伏地的 cushion plants.垫状植物 ¢ Some plants can even survive in favorable有利的 microhabitats微生态小环境 above the snow line. The highest plants in the world occu

15、r at around 6,100 meters on Makalu in the Himalayas. ¢ At this great height, rocks, warmed by the sun, melt small snowdrifts.雪堆 ¢ 在林木线之上有一片区域被广泛地称为高山冻原。毗邻于树带界限，冻土苔原包含一个相当完全被长久存在的灌木、药草牧草覆盖的区域，当高度增加，种类的数量和多样性减少直到零星的苔藓和地衣和一些伏地的垫状植物长在裸露的贫瘠土地。一些植物甚至可以在雪线之上的有利的微生态小环境中生存。世界上最高的植物在喜马拉雅6100米的马卡鲁峰上。

16、在这个高度，岩石被太阳加温，融化了小雪堆。 The most striking惊人的，显著地 characteristic of the plants of the alpine高山 zone is their low growth form. This enables them to avoid the worst rigors寒颤的 of high winds and permits them to make use of the higher temperatures immediately adjacent毗邻 to the ground surface. In an area whe

17、re low temperatures are limiting to life, the importance of the additional heat near the surface is crucial决定性的. The low growth form can also permit the plants to take advantage of the insulation provided by a winter snow cover. In the equatorial mountains the low growth form is less prevalent. 普遍的这

18、些在高山地区的植物的最惊人的特征是他们的低生长形态。这使得他们能够避免最恶劣寒颤的强风且允许他们利用毗邻地表的更高的温度。在一个低温会限制生命的区域，地表的额外的热量的重要性是至关重要的。这种低生长形态也可以使植物利用冬天被雪覆盖的进行隔绝保温。在赤道山群众这种低生长形态是不常见的。GROUNDWATERGroundwater is the word used to describe water that saturates浸透饱和 the ground, filling all the available spaces. By far the most abundant type of gr

19、oundwater is meteoric大气的 water; this is the groundwater that circulates循环流通 as part of the water cycle. Ordinary普通平凡 meteoric water is water that has soaked渗透 into the ground from the surface, from precipitation (rain and snow) and from lakes and streams溪流. There it remains, sometimes for long perio

20、ds, before emerging浮现 at the surface again. At first thought it seems incredible难以置信的 that there can be enough space in the “solid”固体 ground underfoot脚下 to hold储存 all this water. 地下水是一个用来形容浸透土地，充满所有可到达的空间的水。目前为止最充裕的地下水种类是（大气）雨水；这是地下水流通循环作为水循环的一部分。普通大气水是来源于沉淀（雨雪）和溪流湖泊的水从地表浸透到土地里。在水再次浮现到表面之前就呆在那里，这有时是

21、个很长的过程。一开始尽管在脚下的固体的土地有足够的空间去保存所有的这些水看起来难以置信。The necessary space is there, however, in many forms. The commonest spaces are those among the particlessand grains and tiny pebblesof loose,松散的 unconsolidated sand and gravel碎石. Beds of this material, out of sight beneath the soil, are common. They are fo

22、und wherever fast rivers carrying loads负载 of coarse粗糙的 sediment once flowed. For example, as the great ice sheets that covered North America during the last ice age steadily melted away, huge volumes of water flowed from them. The water was always laden with pebbles鹅卵石, gravel碎石, and sand, known as

23、glacial outwash, that was deposited保存堆积 as the flow slowed down. 然而必要的空间是以很多形式存在的。最常见的空间是那些在粒子中砂粒和小卵石宽松的，松散的砂子和碎石。这些材质的水床，在土地下面看不见的地方，是很常见的。他们被发现存在于带着粗糙沉积物的快速流动的河。举个例子，当在上个冰河世纪中的巨大的覆盖着北美洲的冰片逐渐融化，大量的水从冰片中流走了。水中总是混着碎石、砂粒，被称为冰水沉淀，就是在水流减速时堆积下来。The same thing happens to this day, though on a smaller scal

24、e, wherever a sediment-laden river or stream emerges from a mountain valley onto relatively flat land, dropping its load负载 as the current slows: the water usually spreads out fanwise扇形, depositing堆积 the sediment in the form of a smooth, fan-shaped slope. Sediments are also dropped where a river slow

25、s on entering a lake or the sea, the deposited sediments are on a lake floor or the seafloor at first, but will be located inland at some future date, when the sea level falls or the land rises; such beds are sometimes thousands of meters thick. 今天同样的事情发生了，尽管在一个较小的循环中，只要一条沉积物的溪流湖泊从山谷浮现到一个相对平坦的地面上，当水

26、流缓慢是负载的沉积物就会沉淀：水流通常呈扇形展开，沉积物以光滑扇形的斜坡形状堆积下来。当一条河流进入湖泊或海洋而水流缓慢时，沉积物也会沉淀，堆积的沉积物先在河底和海底，但是会在将来当海平面下降或者陆地升高时堆积在中心地带；这样的河床有时可以有几千米深。In lowland country almost any spot地点斑点 on the ground may overlie what was once the bed of a river that has since become buried填埋 by soil; if they are now below the waters upp

27、er surface (the water table), the gravels and sands of the former riverbed, and its sandbars沙洲, will be saturated with groundwater. 在地势低洼的国家几乎任何一个地点都可能曾经是一条已经被土壤填埋的河的河床；如果他们现在在水的上表面之下，原本河床的碎石和砂子和它的沙洲会被地下水浸透。 So much for unconsolidated sediments. Consolidated 坚固的(or cemented粘合的) sediments, too, conta

28、in millions of minute微小的 water-holding pores小孔. This is because the gaps among the original最初 grains are often not totally plugged with cementing chemicals; also, parts of the original最初 grains may become dissolved溶解分解 by percolating渗出的 groundwater, either while consolidation is taking place or at a

29、ny time afterwards. The result is that sandstone, for example; can be as porous多孔能渗透 as the loose松散的 sand from which it was formed. Ordinary普通 以上就是松散的沉积物。坚固的（或者粘合的）沉积物，也同样含有数百万的微小的储水的小孔。这是因为最初颗粒之间的距离通常不是完全的塞满粘合的沉积物的；部分普通颗粒也可能被渗出的地下水溶解，不管是在发生粘合时还是任何粘合之后的时间。结果是举个例子，砂岩可以从它原始形成的样子变得跟松散的砂子一样多孔能渗透。Thus a

30、proportion of the total volume of any sediment, loose or cemented粘合的, consists of empty space. Most crystalline水晶 rocks are much more solid;坚固 a common exception is basalt玄武岩, a form of solidified团结凝固 volcanic火山 lava岩浆, which is sometimes full of tiny bubbles that make it very porous.多孔可渗透 因此所有种类的沉积

31、物中，松散的或者粘合坚固的，相当一部分包含空间（气孔）。大多数结晶岩更加坚固；一个通常的例外就是玄武岩，一种火山岩浆的凝结形式，有事满布小气泡使得它非常多孔可渗透。The proportion of empty space in a rock is known as its porosity. But note that porosity is not the same as permeability, which measures the ease with which water can flow through a material; this depends on the sizes

32、of the individual cavities and the crevices linking them. 岩石中气孔的比例被称为它的多孔性。但注意多孔性和渗透性不一样，渗透性是度量水流可以流过一种材质的难易度；蛋多孔性决定于单个洞和连结他们之间的裂缝大小。 Much of the water in a sample of water-saturated sediment or rock will drain流失 from it if the sample is put in a suitable dry place. But some will remain, clinging附着

33、to all solid surfaces. It is held there by the force of surface tension张力 without which water would drain instantly立即紧急的 from any wet surface, leaving it totally dry. The total volume of water in the saturated浸透的 sample must therefore be thought of as consisting of water that can, and water that can

34、not, drain away. 很多在被水浸透的沉积物或者岩石样本中的水会从岩石中流失如果样本被放在一个适当干旱的地方。但是有些会保持附着在所有固体表面。这是被表面张力吸引，如果没有张力水就会直接从任何湿润的表面流失，留下完全干燥的岩石。被浸透的样本的总水量因此必须被考虑为含有可以流失和不可流失的。The relative amount of these two kinds of water varies greatly from one kind of rock or sediment to another, even though their porosities多孔性adj.porou

35、s may be the same. What happens depends on pore size. If the pores are large, the water in them will exist as drops水滴 too heavy for surface tension张力 to hold, and it will drain away; but if the pores are small enough, the water in them will exist as thin films薄膜, too light to overcome the force of s

36、urface tension holding them in place; then the water will be firmly稳固坚定 held. 这两种水的相对数量在不同沉积物或岩石间变化巨大，尽管他们的多孔性可能相同。变化发生取决于小孔的大小。如果气孔很大，储存在气孔中的水会以水滴的形式存在因为对表面张力太重，且它会流失；但如果气孔足够小，储存在里面的水会以薄面形式存在，太轻以至于不能克服表面张力吸引住它们；然后水会被坚定地吸住。The origin of theaterIn seeking to describe the origins of theater, one must

37、rely primarily主要 on speculation推测, since there is little concrete具体的 evidence on which to draw. The most widely accepted theory, championed by anthropologists人类学家 in the late nineteenth and early twentieth centuries, envisions theater as emerging out of myth神话 and ritual礼仪. The process perceived by

38、these anthropologists may be summarized briefly. During the early stages of its development, a society becomes aware of forces that appear to influence or control its food supply and well-being幸福. Having little understanding of natural causes, it attributes both desirable and undesirable occurrences

39、事件 to supernatural or magical forces, and it searches for means to win the favor偏爱 of these forces. Perceiving认识到 an apparent显然的明显的 connection between certain actions performed by the group and the result it desires, the group repeats, refines改善 and formalizes形式化 those actions into fixed ceremonies仪

40、式, or rituals仪式. 当寻求描述戏剧的起源时，人一定会主要依赖于推测，由于关于从哪里起源少有具体的证据。被19世纪晚期和20世纪早期的人类学家认可也是最广泛被认可的理论预想戏剧起源于神话和礼仪。这些人类学家认知的过程可能被简单总结。在社会发展早期阶段，社会对看上去影响或控制它的食物供给和幸福的力量变得有意识。对自然原因的稀少了解，社会把希望和不希望发生的不良事件都归结于超自然或魔法力量，且它寻求赢取这些力量的方法。意识到某一行为和渴望的结果之间有一个明显联系，社会团体重复，改善和形式化那些行为变成固定的仪式或者礼仪。 Stories (myths) may then grow up

41、 around在什么中发展 a ritual礼仪. Frequently the myths include representatives典型 of those supernatural forces that the rites仪式 celebrate or hope to influence. Performers may wear costumes and masks to represent the mythical characters or supernatural forces in the rituals or in accompanying celebrations. As

42、 a person becomes more sophisticated富有经验久经世故的, its conceptions of supernatural forces and causal relationships may change. As a result, it may abandon or modify修改 some rites. But the myths that have grown up around the rites may continue as part of the groups oral tradition and may even come to be a

43、cted out under conditions divorced from these rites. When this occurs, the first step has been taken toward theater as an autonomous自主自觉 activity, and thereafter entertainment and aesthetic审美 values may gradually replace the former mystical and socially efficacious灵验有效 concerns. 神话可能在仪式后发展起来。这些神话频繁的

44、包含对那些仪式庆贺或者希望去影响的超自然力量的典型。表演者可能穿戏服和面具去代表神话人物或者在礼仪中的伴随着庆祝的超自然力量。（当人变得更加复杂），他们对超自然力量的概念和引发事件之间的关系可能会改变。结果是，人们可能会背弃或者修改一些习俗惯例。但在仪式中发展起来的神话可能继续以社会口头传统（流传）的形式存在甚至在脱离这些习俗时被表演出来。当这种情况出现时，就自主地迈出了发展戏剧的第一步。并且之后的娱乐和审美价值可能逐渐取代之前的神话色彩的和社会灵验的关注。Although origin in ritual has long been the most popular, it is by no

45、 means绝不 the only theory about how the theater came into being. Storytelling故事叙述 has been proposed提议 as one alternative. Under this theory, relating and listening to stories are seen as fundamental human pleasures. Thus, the recalling回忆 of an event (a hunt, battle战役, or other feat功绩) is elaborated详尽

46、 through the narrators叙述者 pantomime手势 and impersonation扮演 and eventually through each role being assumed by a different person. 尽管原始的礼仪已经流行了很长时间，这绝不是唯一一个关于戏剧如何起源的理论。故事叙述已经被建议为一个可选方式。在该理论中，与故事相关和聆听故事被看作是基本的人类乐趣。因此，一个活动（一次打猎，战役，或者其他功绩）的回忆通过叙述者的手势和扮演和最后通过每个角色被每一个不同的人扮演变得详尽。A closely related theory sees

47、 theater as evolving out of 从.发展而来dances that are primarily pantomimic无声, rhythmical有节奏的 or gymnastic体操的, or from imitations模仿 of animal noises and sounds. Admiration for the performers skill, virtuosity精湛技巧, and grace优雅 are seen as motivation for elaborating精心的 the activities into fully realized th

48、eatrical performances. 一个特别相关的理论视戏剧为从舞蹈发展来的主要无声的，有节奏的或者体操的，或者从模仿动物声音。对表演者技巧，精湛技巧，和魅力的赞美被表演者视作活动变为可实现的戏剧表演的动力。In addition to exploring the possible antecedents先祖 of theater, scholars学者 have also theorized about the motives that led people to develop theater. Why did theater develop, and why was it va

49、lued after it ceased停止 to fulfill履行 the function of ritual? Most answers fall back on the theories about the human mind and basic human needs. One, set forth by提出 Aristotle in the fourth century B.C., sees humans as naturally imitative模仿的as taking pleasure in imitating persons, things, and actions a

50、nd in seeing such imitations模仿. Another, advanced in the twentieth century, suggests that humans have a gift for fantasy, through which they seek to reshape重塑 reality into more satisfying forms than those encountered in daily life. Thus, fantasy幻想 or fiction虚构 (of which drama is one form) permits people to objectify具体化 their anxieties焦虑 and fears, confront面对 them, and fulfill实现履行 t