Part five Ecosystem Ecology Contents of Part Five 一、Ecosystem energetics 二、Decomposition and Nutrient Cycling 三、Biogeochemical Cycles Outlines of this part 1.The Laws of Thermodynamics Govern Energy Flow 2. Energy fixed in the process of photosynthesis is primary production 3. Factors influencing Primary Production 4. Primary production varies with time 5. Primary productivity limits secondary production 6. Consumers vary in efficiency of production 7. Ecosystem have two major food chains 8. Energy flow through tropic levels can be quantified 9. Consumption efficiency determines the pathway of energy flow through the ecosystem 10. Energy decreases in each successive trophic level 1.The Laws of Thermodynamics Govern Energy Flow The first law of thermodynamics states that Energy is neither created nor destroyed. The second law of thermodynamics states that when energy is transferred or transformed, part of the energy assumes a form that cannot pass on any further. Entropy increases. Energy flow of ecosystem • Energy flow is a one-directional process. • • sun---> heat (longer wavelengths) FIRST LAW of THERMODYNAMICS: Energy can be converted from one form to another, but cannot be created or destroyed. SECOND LAW of THERMODYNAMICS • Transformations of energy always result in some loss or dissipation of energy能量转化过程中一定伴随着损失 • or • In energy exchanges in a closed system, the potential energy of the final state will be less than that of the initial state封闭系统中 最终稳定状态下的能量必低于初始水平 • or • Entropy tends to increase (entropy = amount of unavailable energy in a system)熵值增加 • or • Systems will tend to go from ordered states to disordered states (to maintain order, energy must be added to the system, to compensate for the loss of energy)系统总是趋向于无序化(如 果要维持有序,系统则需要消耗能量补偿能量损失) Internal combustion engines in cars are 25% efficient in converting chemical energy to kinetic energy; the rest is not used or is lost as heat. 2. Energy fixed in the process of photosynthesis is primary production Gross primary productivity (GPP): Total rate of photosynthesis Net primary productivity (NPP): rate of energy as storage as organic matter after respiration NPP=GPP-R • Primary production is the production of organic compounds from atmospheric or aquatic carbon dioxide, principally through the process of photosynthesis, with chemosynthesis being much less important. All life on earth is directly or indirectly reliant on primary production. • The organisms responsible for primary production are known as primary producers Photosynthesis Energy change Chloroplast ultra structure Plant cells with visible chloroplasts Leaf in light 2,地球上初级生产力的分布 Standing crop biomass: amount of accumulated organic matter in an area at a given time Biomass is expressed as g organic matter per square meter (g m-2) Productivity is the rate at which organic matter is created by photosynthesis (g m-2 yr-1) How to measure? Terrestrial ecosystem: Change in standing crop biomass over a given time interval (see Hui & Jackson 2006 for grasslands) Aquatic ecosystem: 黑白瓶测氧法 一、测定原理 Bottle Light Bottle Dark bottle 将几只注满水样的白瓶和黑瓶悬挂在采水深度处,曝光24 小时,黑瓶中的浮游植物由于得不到光照只能进行呼吸作用, 因此黑瓶中的溶解氧就会减少; 而白瓶完全曝露在光下,瓶中的浮游植物可进行光合作用, 因此白瓶中的溶解氧量一般会增加。因此,通过黑白瓶间溶 解氧量的变化,就可估算出水体的生产力。 黑白瓶测氧法 二、测定方法和步骤 1. 采水与挂瓶 2. 溶解氧的固定与分析 曝光结束,立即取出黑瓶和白瓶,加入MnSO4和碱性碘化 钾进行固定,充分摇匀后,测定溶氧量。 黑白瓶测氧法 三、计算方法 各挂瓶水层日生产量(mgO2/L)的计算 GPP=白瓶溶解氧一黑瓶溶解氧 NPP=白瓶溶解氧一原始瓶溶解氧 R=原始瓶溶解氧一黑瓶溶解氧 毫克/升·日(mg/L·d) 3. Factors influencing Primary Production Net primary productivity for a variety of terrestrial ecosystem as a function of mean annul precipitation (MAP) and mean annual temperature (MAT) as well as length of growing season N P P Deciduous forest in N. America Warm temperature and adequate water supply for transpiration that gives the highest primary productivity. (Remember that photosynthesis and transpiration are coupled processes) Global map of primary productivity Patterns of productivity reflect global patterns of temperature and precipitation. High NPP in equatorial zone and coastal region. Primary production varies with nutrient availability Different forest ecosystems RO, red oak; RP, red pine; SM, sugar maple, Hem, hemlock; WP, white pine 20 oak savanna in Minnesota in aquatic ecosystems Changes in available light, respiration, NPP with water depth Compensation depth: Depth that available light is equal to the light compensation point (NPP=0 or GPP=R) Geographic variation in primary productivity of world’s oceans 1.Great transport of nutrient from bottom to top 2.Nutrient from terrestrial ecosystems High productivity is along coastal regions 4. Primary production varies with time Park Grass, Rothamsted Experimental Station in England Climatic variation Disturbance Stand aging 5. Primary productivity limits secondary production Net primary production is the energy available to the heterotrophic component of the ecosystem Secondary production: net energy of production of secondary consumers •Consumed( waste products) •assimilated (respiration) •Reminder is available for maintenance – capturing or harvesting food etc, and lost as heat •Energy left over from maintenance and respiration goes into production, including growth of new tissues and production of young Secondary productivity: secondary production per unit of time Secondary production depends on primary production for energy 69 studies for terrestrial ecosystems (from Arctic tundra to tropical forests) Sam McNaughton,1989 Similar relationship in lake ecosystems 43 lakes+12 reservoirs Tropic to Arctic Bottom-up and topdown control TROPHIC STRUCTURE • Trophic structure is the pattern of movement of energy and matter through an ecosystem. • It is the result of compressing a community food web into a series of trophic levels. green and brown food webs Green food web Brown food web TROPHIC STRUCTURE 2O & HIGHER LEVEL CONSUMERS 1O CONSUMERS PRODUCERS • The result of combining all producers and consumers in Hubbard Brook would be a biomass pyramid. • Since consumers can be at several trophic levels, the fraction of the food they consume at each trophic level is determined and proportioned among levels. TROPHIC STRUCTURE 2O & HIGHER LEVEL CONSUMERS DECOMPOSERS 1O CONSUMERS PRODUCERS Detritivores (species that feed on the dead remains of organisms) are also known as decomposers. These include bacteria, fungi and invertebrate animals of numerous species. Lindeman's efficiency • The ratio of energy assimilated at one trophic level to that assimilated at the preceding trophic level; the ratio of energy intake at successive trophic levels. It is one of the earliest and most widely applied measures of ecological efficiency. 10%? Less than 6O Ecological efficiency • the efficiency with which energy is transferred from one trophic level to the next. It is determined by a combination of efficiencies relating to organismic resource acquisition and assimilation in an ecosystem. 6. Consumers vary in efficiency of production P426 P A I R W Parameters • Ingestion 摄食量(I): • Assimilation 同化量(A): • Respiration 呼吸量(R): • Production 生产量(P):P = A - R。 assimilation efficiency 同化效率 Ae = A n / I n production efficiency 生产效率 Pe = P n / A n Energy Loss – Energy flow ,not Energy cycling Energy lost as heat consumption efficiency (Pg 177) 消费效率 Ce=In+1/Pn Lindemans efficiency 林德曼效率 是指n+1营养级所获得的能量占n营养级获得能量之比, 相当于同化效率、生长效率与消费效率的乘积。 Le = An/In×Pn/An×In+1/Pn = In+1/In= An+1 / An Law of 1/10 1915—1942 Cedar Bog Lake Assimilation efficiency • Vary widely among animal groups • Endotherms(内温动物) are much more efficient than ectotherms(外温动物) • Carnivorous animals (肉食动物) (even ectothermic ones) have high assimilation efficiency than herbivores (草食动物) (meat vs veg) Production efficiency varies mainly according to taxonomic class 7. Ecosystem have two major food chains 捕食食物链 碎屑食物链 Within any ecosystem, there are two major food chains Difference 1. Source of energy for herbivores 2. Energy flow direction 3. interconnected 8. Energy flow through tropic levels can be quantified Energy flow within a single trophic compartment Consumption efficiency: In/Pn-1 9. Consumption efficiency determines the pathway of energy flow through the ecosystem In terrestrial ecosystems and shallow water ecosystems, with their high standing biomass and relative low harvest of primary production by herbivores, the detrital food chain is dominate. In deep water aquatic ecosystem, with low biomass, rapid turnover and high rate of harvest, grazing chain may be dominate. P434 10. Energy decreases in each successive trophic level • Trophic efficiency (TE) is the ratio of productivity in a given trophic level (pn) to the trophic level it feeds on (Pn-1): TE=Pn/Pn-1 • Ecological pyramids are graphical representations of the trophic structure of a given ecosystems A universal diagram of energy flow A universal diagram of energy flow P.E.Odum,1968 Characteristics of Energy flow: One-way flow Descent by trophic levels Summary 1.The Laws of Thermodynamics Govern Energy Flow 2. characteristics of energy flow are one-way flow and descent by trophic levels 3. Factors including temperature, precipitation and growing seaon, controlling Primary Production 4. Primary productivity can be measured by the method of light and dark bottle in aquatic ecosystem, and by calculating change standing crop biomass over a given time interval in terrestrial ecosystem. 5. Primary productivity limits secondary production 6. Consumption efficiency determines the pathway of energy flow through the ecosystem——Grazing food chain and Detrial food chain Question • Please expound the relationship between primary production and secondary production.
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