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1、P1 组成成员和过程 要 点生态系统的概念1935年Tansley提出生态系统的概念，最初的定义包括一个定义的空间中所有的动物、植物和物理的相互作用。近代生态学家更倾向于从能（量）流、碳流或营养物流来考虑生态系统。水生生态系统陆地生态系统The ecosystem concept was proposed by Tansley in 1935, and was originally defined to include all the animals, plants and physical interactions of a defined space. Modern ecologists
2、tend to think of ecosystems in terms of energy flow, carbon flow or nutrient cycles. Key NotesThe concept the ecosystemP1 COMPONENTS AND PROCESSES生态系统成分单位面积中活有机体的身体构成了生物量（biomass）的现存量（standing crop）：单位地（或水）面积的有机体的质量，通常以能量或干有机质为单位（例如t/ha）陆地群落大部分生物是植被。群落初级生产率是初级生产者植物所生产的单位面积生物量的速率。通过光合作用固定的总能量是总初级生产量（
3、GPP），其中一部分从群落丢失于呼吸作用（R）。GPP与R之差称为净初级生产量（NPP），它代表了新生物量的产生速率，并可供异养生物（细菌、真菌和动物）消费之用。被异养生物生产的生物量叫做次级生产量。The bodies of living organisms within a unit area constitute a standing crop of biomass: the mass of organisms per unit area of organisms per unit area of ground (or water), usually expressed in units
4、 of energy or dry organic matter (e.g. tons ha-1). The great majority of biomass in a terrestrial community I is the rate at which biomass is produced per unit area by plants, the primary producers. The total fixation of energy by photosynthesis is referred to as gross primary productivty (GPP) of w
5、hich a proportion (R) is lost form the community as respiration. The difference between GPP and R is known as net primary productivity (NPP) and represents the rate of production of new biomass that is available for consumption by heterotrophic organisms (bacteria, fungi and animals). The production
6、 of biomass by heterotrophs is called secondary production.Ecosystem components 生态系统与热力学定律热力学第一定律说明，能量既不能被创造，也不能被破坏。热力学第二定律说明，每一次“转换都导致系统的自由能的减少”。因为能量转换不可能100%的有效，因此异养生物的能量较少，必然比它们所吃的植物更少。生态相互作用的复杂性意味着，以这些热力学定律为基础去构建用于预测的数学模型是不可能的。The first law of thermodynamics states that energy can neither be cre
7、ated nor destroyed. The second law of thermodynamics states that every transformation results in a reduction of the free energy of the system. Because energy transformation cannot be 100% efficient (from the second law), heterotrophs must have less energy,and must therefore be rater than the plants
8、they feed on. The complexity of ecological interactions means that it is not possible to construct predictive mathematical models of living systems based on these laws of thermodynamics.Ecosystems and the laws of thermodynamics转换效率净初级生产力通过营养级流动的比例，决定于能量从一级到下一级的利用、通过途中的转化效率。正是三类转换效率的全部知识，是预测能量流动格局的全部
9、要求，那就是消费效率（CE）、同化效率（AE）和生产效率（PE）。消费效率是指一个营养级的有效总生产力（P n-1）中，后一营养级成员实际消费（被吃掉）部分（I n）所占的百分比。同化效率是指一个营养级的消费者吃入消化道的食物能量（In）中，被同化而穿过消化道壁、并成为参加生长或用于作功的有效能量（A n）所占的百分比。生产效率是指被同化的能量中（A n），加入到新生物量（P n）所占的百分比。剩留下来的完全以呼吸热量而损失于群落。The proportion of net primary production that flows through trophic levels depends
10、 on transfer efficiencies in the way energy is used and passed from one step to the next. A knowledge of just three categories of transfer efficiency is all that is required to understand the pattern of energy flow. These are consumption efficiency (CE), assimilation efficiency (AE) and production e
11、fficiency (PE). Consumption efficiency is the percentage of total productivity available at one trophic level (Pn-1) that is actually consumed (ingested) by a trophic compartment one level up (In). Assimilation efficiency is the percentage of food energy taken into the guts of consumers in a trophic
12、 compartment (In) which is assimilated across the gut wall (An) and becomes available for incorporation into growth or used to do work. Production efficiency is the percentage of assimilated energy (An) which is incorporated into new biomass (pn). The remainder is entirely lost to the community as r
13、espiratory heat.Transfer efficiencies 通过群落的能流如果净初级生产量和CE、AE和PE是已知的值，那么运用模型预测不同群落各个营养级的能流途径是可能的。从这种有野外数据支持的模型研究得到了一个有意义的发现，即分解者系统是非常重要的。有普遍意义的是，在状态稳定的群落里，动物呼吸所丢失的被NPP所平衡，所以现存生物量保持一样的水平。相关主题初级和次级生产力（见P2） 群落、结构和稳定性（见Q1）食物链（见P3） 群落格局、竞争和捕食（见Q3）Related topicsPrimary and secondary production The community
14、, structure and (P2) stability (Q1)Food chains (P3) Community patterns, competition and predation (Q3)Energy flow through a communityGiven that specified values can be obtained for not primary production and CE, AE and PE, it is possible to predict, using models, the pathway of energy flow at differ
15、ent trophic levels for different communities. From such modeling studies, which are supported by field data, the most significant finding is the overwhelming importance of the decomposer system. Overall, in a steady state community, losses through animal respiration balance NPP so that standing crop
16、 biomass remains the same.P2 初级和次级生产力 要 点初级生产力全球陆地的净初级生产力大约为12010 9 t / a干物质，而海洋的大约为50 10 9 t / a干物质。这种生产力在地球上分布是很不均匀的。最富有生产力的系统出现在沼泽、湿地、河口湾、珊瑚礁和耕田。生产力随离赤道距离增大而降低，它表明温度与辐射的重要性。红树林沼泽 江源湿地 Global net primary productivity is approximately 120109 tons fry weight per year on land, and 50109 tons per year
17、 in the sea. This productivity is very unevenly distributed across the Earth. The most productive systems are found amongst swamp and marshland, estuaries, reefs and cultivated land. Productivity decreases moving away from the equator, indication the importance of temperature and radiation.Key Notes
18、Primary productionP2 PRIMARY AND SECONDARY PRODUCTION生产力对生物量的关系通过生产力（P）与现存生物量（B）之比，可以把群落生产力与产生它的现存量联系起来。对于森林，所得到的P：B比率（即每年每公斤现存量所生产出的公斤数）平均为0.042，其他陆地系统是0.29，而水体群落是17.0。考虑P：B比率的另一种选择是以活组织的重量确定的生物量，它将缩小群落之间的这些大的区别。当然，精确测定活的生物量比例是很困难的事。Community productivity can bi related to the standing crop that pr
19、oduces it by comparing the ratio of productivity (P) to standing crop biomass (B). The resulting P:B ratios (I.e kg produced year-1 kg-1 standing crop) average 0.042 for forests, 0.29 for other terrestrial systems, and 17.0 for aquatic communities. An alternative way of looking at P:B ratios would b
20、e to define biomass in terms of weight of living tissue, which would reduce these large differences between communities. However, accurate measurement of the proportion of biomass alive is difficult.Relationship of productivity to biomass次级生产力次级生产力的定义是异养有机体的新生物量的生产速率。异养生物如动物、真菌，要求能量丰富的有机分子。异养生物的次级生产
21、力必然地依存于初级生产力。一般说来，在牧食者系统中，次级生产力是群落营养结构中，依存于消费活植物生物量的那一部分，在数量级少于植物生产力，从而形成了金字塔结构。然而也有例外。西藏大型经济真菌 Secondary production is defined as the rate of production of new biomass by heterotrophic organisms. Heterotrophs are organisms, such as animals and fungi, with a requirement for energy-rich organic molec
22、ules. Secondary production by heterotrophs is inevitably dependent on primary productivity. Generally, in grazer systems, that part of the trophic structure of a community which depends on the consumption of living plant biomass, secondary productivity is an order of magnitude less than primary prod
23、uction resulting in a pyramidal structure. However, there are exceptions to this.Secondary production相关主题太阳辐射与植物（见F1） 组成成员和过程（见P1）植物与消费者（见G2） 食物链（见P3）物质与能量的关系能量一旦转化为热，它就不再能被有机体用于作功或合成生物量的燃料。热损失到大气中，再也不能进入再循环。地球上生命所以能够存在，正是由于太阳辐射每天都提供着新鲜的可用能量。相反，像碳一样的营养物，就能被再利用。构成生物量基块的化学营养物可以被利用，以临界的特征在再循环着。与太阳辐射的能量
24、不同，营养物的供应不是不会改变的。如果植物及其消费者没有被最后分解掉，营养物的供应将会耗尽，地球上的生命也将终止。太阳辐射Related topicsSolar radiation and plants (F1) Components and processes (P1)Plants and consumers (G2) Food chains (P3)The relationship between matter and energyOnce energy is transformed into heat, it can no longer be used by living organis
25、ms to do work or to fuel the synthesis of biomass, the heat is lost to the atmosphere and can never be recycled. Life on Earth is possible because a fresh supply of solar energy is made available every day, In contrast, nutrients such as carbon can be reused. Chemical nutrients, the building blocks
26、if biomass, can be used again, and recycling is a critical feature. Unlike the energy in solar radiation, nutrients are not in unalterable supply of nutrients would become exhausted and life on Earth would cease.3 食物链 要 点营养物流自养生物同化无机资源，生成有机分子的组件，这些组件成为异养生物的资源，后者又后为另一个消费者的资源。在这种食物链的每一个连接，我们能够辨别出通向下一个
27、营养级的三条途径：分解、寄生和捕食。消费者可能是泛化种（多食性的），吃广范围的猎物种，或者是特化为吃一个或一组有密切关系的种（单食性的）。血吸虫寄生部位 Autotrophic organisms assimilate inorganic resources into packages of organic molecules. There become the resources for heterotrophs which then become a resource for another consumer. At each link in this food chain we can
28、recognize three pathways to the next trophic level: decomposition, parasitism and predation. Consumers may be generalists (polyphagous), taking a wide variety of prey species or may specialize on single species or a range of closely related species (monophagous). Key NotesPathways of nutrient flowP3
29、 FOOD CHAINS营养级间的相互作用生态系统的一个特征是：占据其各个营养级的种数及种的性质。一个营养级的成员与邻近营养级的成员之间的相互关系可以用食物链来描述。食物链是连接吃与被吃的链，例如，食肉动物到它的最后的植物食物。任何生态系统都有许多食物链，并可以组成食物网。生态系统在能量-营养物网的模式上有很大的变化。食物链A characteristic of an ecosystem is the number and nature of the species that occupy its various trophic levels. The relationship between
30、 constituents of one trophic level and constituents of adjacent trophic levels may be described by a food chain. This is a chain of eating and being eaten that connects, for example, carnivorous animals to their ultimate plant food. Many food chains exist in any given ecosystem and van be combined i
31、nto food webs. Ecosystems vary considerably in the pattern of their energy-nutrient webs.Interactions between trophic levels下行或上行曾经有过辩论，地球是绿色的、长满植被的，这是因为食草动物被其捕食者所调节（下行控制，top-down control），而所有别的营养级都是被资源竞争所调节的（上行控制，buttom-up control）。这个简单的模型是吸引人的，但是其价值是值得怀疑的。由于植物有防御，食草物种在它们所吃的植物组织的范围方面是受到很大限制的；因此，即使世
32、界是绿色的，它们也可能受到竞争的限制。不仅如此，植物大体上并不受能量的限制，但却受到空间限制，所以任何被食草动物清出的空间，都为更多的植物开放的机会。食草动物食肉动物Top-down or bottom-up?It has been argued that the earth is green and vegetated because herbivore numbers are regulated by their predators (top-down control), whilst all other trophic levels are regulated by competitio
33、n for resources (bottom-up control). This simple model is attractive but of doubtful value. Herbivore species are highly constrained in the range of plant tissue they can eat, due to plant defences, and hence may be level, plants are not energy-limited but space limited, so any space cleared by herb
34、ivory opens opportunities for more plants.相关主题捕食的性质（见J1） 初级和次级生产力（见P2）捕食行为和猎物反应（见J2）群落格局、竞争的捕食（见Q3）群落、结构和稳定性（见Q1） 组成成员和过程（见P1）寄生的性质（见K1）Related topicsThe mature of predation (J1) Primary and secondary productionPredator behavior and prey (P2) response (J2) The community, structure and The nature of parasitism (K1) stability (Q1)Components and processes (P1) Community patterns, competition and predation (Q3)
