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
3、初级生产量（ 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 expre
4、ssed in units 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 productiv
5、ty (GPP) of which 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). T
6、he production 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 ca
7、n neither be created 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
8、than the plants 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
9、全部知识，是预测能量流动格局的全部要求，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 f
10、lows through trophic levels depends 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), assimilati
11、on efficiency (AE) and production efficiency (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
12、 the guts of consumers in a trophic 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 respiratory heat.Transfer efficiencies
