农业生态学国家精品课程(第三章)课件

1、第三章 能量流动Chapter 3 Energy flow 2022/9/261国家级精品资源共享课2022/9/26国家级精品资源共享课2一、能量转移二、农业生态系统遵守能量流动的基本规律三、食物是农业生态系统中的能量载体四、农业生态系统的能源、能流途径和能效五、农业生态系统的能流调控主要内容2022/9/26国家级精品资源共享课3（一）能量转移 植物利用太阳能，通过光合作用生产食物能，食物能通过食物链和食物网，从一个营养级传递到另一个营养级。太阳能 绿色植物 食草动物 食肉动物一、能量转移The relationship between matter and energy Once ene

2、rgy is transformed into heat, it can no longer be used by living organisms 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, nutrient

3、s such as carbon can be reused. Chemical nutrients, the building blocks if biomass, can be used again, and recycling is a critical feature. Unlike the energy in solar radiation, nutrients are not in unalterable supply. If plants, and their consumers were not eventually decomposed, the supply of nutr

4、ients would become exhausted and life on Earth would cease.2022/9/265国家级精品资源共享课2022/9/26国家级精品资源共享课61.流生态系统中能量和物质不断地被吸收、贮存和转移的运动状态。能量的转移能量流。物质的转化物质流。流量要多，流速要快 增加流量的方法：提高能量转化效率、减少消耗 增加流速的方法：缩短周转周期、提高周转速率（二）流、库、环的概念及应用2022/9/26国家级精品资源共享课72.库能量和物质在运动过程中暂时被吸收和贮存的单位。库要大、库效率要高。（1）植物库：库大土地利用充分、植物产品多；库效率高光合效

5、率高（2）动物库：库大种群多数量大、动物产品多；库效率高出栏率高，产肉蛋奶多（3）土壤库：库大土壤肥力高而稳库效率高养分损失少，利用率高 2022/9/26国家级精品资源共享课83.环各种库将流连接起来形成的整体。环结构要合理 环流库是相互联系的。库要大、效率高；环结构要合理；流要多且流畅。2022/9/26国家级精品资源共享课10The first law of thermodynamics states that energy can neither be created nor destroyed. The second law of thermodynamics states that

6、 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 rarer than the plants they feed on. The complexity of ecological interactions means t

7、hat it is not possible to construct predictive mathematical models of living systems based on these laws of thermodynamics.Ecosystems and the laws of thermodynamics2022/9/26国家级精品资源共享课121.根据热力学第一定律，可以对农业生态系统的能量流进行定量研究。2.在农业生态系统能量流中，只有少部分转化成有机形态的化学潜能储存起来，大部分转化成热能而耗散。3.能量流的流动方向是不可逆的，能量只能称为转化或转移，而不能是循环。

8、4.为了维持农业生态系统的稳定，应不断的向系统输入能量，减少熵。(四)热力学定律在农业生态系统中的应用 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 recognize three pathways

9、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). Pathways of nutrient flow2022/9/2614国家级精品资源共享课食物链2022/9/2615国

10、家级精品资源共享课 A characteristic of an ecosystem is the number and nature of the species that occupy its various trophic levels. The relationship between 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 eate

11、n that connects, for example, carnivorous animals to their ultimate plant food. Many food chains exist in any given ecosystem and can be combined into food webs. Ecosystems vary considerably in the pattern of their energy-nutrient webs.Interactions between trophic levels2022/9/2616国家级精品资源共享课Top-down

12、 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 competition for resources (bottom-up control). This simple model is attractive but of doubtful value

13、. Herbivore species are highly constrained in the range of plant tissue they can eat, due to plant defences, and hence may be limited by competition even if the world is green. Further, at a gross level, plants are not energy-limited but space limited, so any space cleared by herbivory opens opportu

14、nities for more plants.2022/9/2617国家级精品资源共享课一个食物链的例子“螳螂捕蝉，黄雀在后”螳螂捕蝉，黄雀在后！哈！哈！植物汁液蝉(初级消费者)螳螂(二级消费者)黄雀(三级消费者)鹰(四级消费者)(顶极食肉动物)2022/9/2618国家级精品资源共享课（3）寄生食物链植物型：大豆菟丝子动物型：哺乳动物跳蚤原生动物细菌病毒；马蛔虫（4）混合食物链 稻草牛（牛粪）蚯蚓鸡（鸡粪）猪（猪粪）鱼；稻螟赤眼蜂；菜（温棚）鸡（鸡粪）沼气（沼渣）肥田2.营养级：生物在食物链上所处的位置，即食物链上每一个环节称为营养级。2022/9/2620国家级精品资源共享课2022/9/

15、26国家级精品资源共享课21海洋生态系统的食物链 生产者420108吨年食草动物64108吨年第1级食肉动物10108吨年第2级食肉动物1.5108吨年 第3级食肉动物0.22108吨年2022/9/26国家级精品资源共享课23海洋与陆地生态系统的食物链2022/9/26国家级精品资源共享课24（1）同一食物链中常含有食性和生活习性极不相同的生物。（2）同一生态系统中可能有多条食物链，各种食物链相互联系，协同发挥作用。（3）自然生态系统中，营养级的数目是有限的。（4）不同生态系统中，各类食物链的比重不同。森林生态系统：腐生食物链占生产有机物的90%草原生态系统：腐生食物链占生产有机物的70%农

16、田生态系统：腐生食物链占生产有机物的20%30%3.食物链的基本特征Food Webs Illustrate Complex Trophic Relationships2022/9/2626国家级精品资源共享课2022/9/26国家级精品资源共享课27 生态系统抵抗外界干扰、自动修复的能力称为生态系统的稳定性。影响稳定性的因素有很多，如生物的适应性、外界干扰的程度、营养结构等。 营养结构复杂、食物网复杂的生态系统，稳定性强2.营养结构与生态系统的稳定性2022/9/26国家级精品资源共享课28（一）农业生态系统的能源1.太阳能是生态系统的主要能源2.农业生态系统的辅助能辅助能的类型：自然辅助能

17、、人工辅助能：生物辅助能（有机能）、工业辅助能（无机能）辅助能的性质：不能转化成生物能，对生物能的合成、转化起辅助作用辅助能的作用：促进转化、减少消耗、改善环境四、农业生态系统的能源、能流途径和能效生态系统中的能量流动 输入生态系统中的能量（太阳能）总是和生物有机体贮存、转换的能量和释放的热量相等。 以热的形式散失的能量不能再回到生态系统参与流动和被利用2022/9/2630国家级精品资源共享课Connections: Food Chains and Energy Flow in EcosystemsEcological efficiency=10%Loss?2022/9/2631国家级精品资

18、源共享课Primaryproducers100 J1,000,000 J of sunlight10 J1,000 J10,000 JPrimaryconsumersSecondaryconsumersTertiaryconsumers2022/9/2632国家级精品资源共享课The dynamics of energy through ecosystems have important implications for the human population.2022/9/2633国家级精品资源共享课Energy flow through a community Given that sp

19、ecified values can be obtained for net primary production and CE, AE and PE, it is possible to predict, using models, the pathway of energy flow at different trophic levels for different communities. From such modeling studies, which are supported by field data, the most significant finding is the o

20、verwhelming importance of the decomposer system. Overall, in a steady state community, losses through animal respiration balance NPP so that standing crop biomass remains the same.2022/9/2634国家级精品资源共享课太阳辐射能 24%52%云层吸收10 %浮尘15%反射25%臭氧层、水蒸气等9% 24%地球表面47%反射4%散射6%散射17%散射损失9%2022/9/2635国家级精品资源共享课2022/9/2

21、6国家级精品资源共享课36一个稳定生态系统的能量流分解者消费者呼吸、热量生产者呼吸、热量腐生生物分解和呼吸及热量生产者太阳辐射能输入消费者消费者消费者未利用未利用2022/9/26国家级精品资源共享课372022/9/26国家级精品资源共享课38Ecosystem Energy Flow生态系统的能流能流特征逐级减少单方向性能流路径2022/9/2639国家级精品资源共享课Assimilatory:同化的 Dissimilatory：异化的2022/9/2640国家级精品资源共享课2022/9/26国家级精品资源共享课41 1.能量流动过程中损耗的必然性（1）由于不可食或不得食（2）消费者密度

22、低或食物选择限制 （3）利用后未被同化（4）同化后呼吸消耗掉（5）变为生产量又被减少 营养级能量传递效率约平均为10%。（三）农业生态系统的能效和生态金字塔规律2022/9/26国家级精品资源共享课422.能量传递效率（生态效率）：通常指食物链各环节上能量的各种转化效率。肉猪35%、奶牛 20%、蛋鸡15%、肉兔1318%、肉羊11%、肉牛58%。2022/9/26国家级精品资源共享课43新陈代谢、生长和运动是生命的基本功能 物理运动化学运动生命运动 2022/9/26国家级精品资源共享课443.生态金字塔规律 生态金字塔是生态学研究中用以反映食物链各营养级之间生物个体数量、生物量和能量比例关系的一个图解模型。类型 数量金字塔树木昆虫鸟类（畸形金字塔）生物量金字塔浮游植物浮游动物底栖动物（倒置金字塔）能量金字塔能量金字塔能量能量流失2022/9/2645国家级精品资源共享课2022/9/26国家级精品资源共享课46Biomass and productivity generally decrease with trophic levelHence t