Lecture 9: Ecosystem Ecology (Energy in the Ecosystem)

1. Lecture 9: Ecosystem Ecology (Energy in the Ecosystem) Huang He Phone: 18972127775 QQ:105367750 E-mail: hn.huanghe@163.com PPT模板下载：www.1ppt.com/moban/ 行业PPT模板：www.1ppt.com/hangye/ 节日PPT模板：www.1ppt.com/jieri/ PPT素材下载：www.1ppt.com/sucai/ PPT背景图片：www.1ppt.com/beijing/ PPT图表下载：www.1ppt.com/tubiao/ 优秀PPT下载：www.1ppt.com/xiazai/ PPT教程： www.1ppt.com/powerpoint/ Word教程： www.1ppt.com/word/ Excel教程：www.1ppt.com/excel/ 资料下载：www.1ppt.com/ziliao/ PPT课件下载：www.1ppt.com/kejian/ 范文下载：www.1ppt.com/fanwen/ 试卷下载：www.1ppt.com/shiti/ 教案下载：www.1ppt.com/jiaoan/

3. Ecosystem Definition: biotic community and abiotic environment functioning as a system. Includes organism-complex and whole complex of physical factors. Forest Ecosystem Forest is a system composed of autographs, heterographs, and abiotic environment, each component processing and exchanging energy and matter. Inputs: exchanges from the surrounding environment into the ecosystem Outputs: exchange from inside ecosystem to the surrounding environment Closed ecosystem: an ecosystem with no inputs and outputs Open ecosystem: an ecosystem with inputs and outputs Ecosystem ecology: exchanges of energy and matter between ecosystem and environment and among components within the ecosystem (energy flow and nutrient cycling).

4. Outline 9.1 Ecosystem function obeys thermodynamic principles 9.2 Primary production provides energy to the ecosystem 9.3 Many factors influence primary production 9.4 Primary production varies among ecosystems 9.5 Only 5%– 20% of assimilated energy passes between trophic levels 9.6 Energy moves through ecosystems at different rates 9.7 Ecosystem energetics summarizes the movement of energy populations

5. 9.1 Ecosystem function obeys thermodynamic principles History of Ecosystem Ecology Alfred J. Lotka, 1925 Energy transformation and thermodynamic principles Raymond Lindeman, 1942 Pyramid of energy (left) Eugene Odum, University of Georgia, 1953 Fundamentals of Ecology

6. E. P. Odum developed a “ universal” model of energy flow through ecosystems. The energy ingested by organisms at each trophic level is reduced by respiration and excretion, so that less energy is available for consumption by the next trophic level.

7. Laws of thermodynamics govern energy flow First law of thermodynamics: Energy is neither created nor destroyed. Second law of thermodynamics When energy is transferred or transformed, part of the energy assumes a form that cannot pass on any further. As energy is transferred from one organism to another in the form of food, a portion is stored as energy in living tissue, whereas a large part of that energy is dissipated as heat.

8. 9.2 Primary production provides energy to the ecosystem Flow of energy through a terrestrial ecosystem starts with the harnessing of sunlight by autotrophs. Rate at which light energy is converted by photosynthesis to organic components is referred to as primary productivity. 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

10. Productivity is the rate at which organic matter is created by photosynthesis (g m-2 yr-1) 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)

11. How to measure? Terrestrial ecosystem: 1. Flux based Measure photosynthesis (equipment: LiCor, Eddy flux method) net photosynthesis 2. Biomass based estimation Change in standing crop biomass (SCB) over a given time interval NPP=delta SCB +loss of biomass due to death of plant + loss due to consumption. (see Hui & Jackson 2006 for grasslands)

12. How to measure? Aquatic ecosystem:

14. 9.3 Many factors (light, temperature, water, and nutrients) influence primary production Light and Temperature Precipitation/water Nutrients CO2

16. Photosynthetic efficiency • Photosynthetic efficiency is the percentage of the energy in sunlight that is converted to net primary production during the growing season. • Photosynthetic efficiency: 1-2% • What happens to the remaining 98%– 99% of the light energy? Some of it is assimilated during photosynthesis and later respired. Leaves and other surfaces reflect any­where from 25% to 75% of the light energy. Molecules other than photosynthetic pigments absorb most of the remainder, which is converted to heat and either radiated or conducted across the leaf surface or dissipated by the evaporation of water from the leaf ( transpiration).

17. Plant temperatures reflects their energy balance with the surrounding environment • Different responses of photosynthesis and respiration to temperature; • Three basic Temperature points • Min T, max T and optimal T Optimal T: 16 oC for temperate plants, as high as 38oC for some tropical species

18. Temperature and precipitation on terrestrial ecosystem productivity

19. Precipitation and temperature Net primary productivity for a variety of terrestrial ecosystem as a function of mean annual precipitation (MAP) and total annual temperature (MAT).

20. Warm temperature and adequate water supply for transpiration that gives the highest primary productivity. (Remember that photosynthesis and transpiration are coupled processes)

21. Water use efficiency • Trade-off • To carry out photosynthesis, plants must open up the stomata to get CO2; • Transpiration loss of water to atmosphere. • WUE: ratio of carbon fixed (photosynthesis) per unit of water lost (transpiration) WUE: dry grassland, 0.2 g dry matter per kg water C3 crops 1.6 C4 crops 3.1 CO2 increases WUE

22. Primary production varies with nutrient availability Different forest ecosystems RO, red oak; RP, red pine; SM, sugar maple, Hem, hemlock; WP, white pine (J. Pastor) 20 oak savanna in Minnesota (P. Reich)

23. McMaster et al. 1982

25. Nutrient use efficiency ( NUE) Nutrient use efficiency ( NUE): the ratio of dry matter production to the assimilation of a particular nutrient element, usually expressed as grams per gram. The NUE for nitrogen, for example, is expressed as grams of dry matter produced per gram of nitrogen assimilated. NUE: crop plants vary widely, 50– 300 g per g for nitrogen 300– 1,500 g per g for phosphorus

26. Effects of nutrient addition on marine phytoplankton growth rate in 303 experiments John downing, Iowa State Conducted 303 experiments Nitrogen addition stimulated phytoplankton growth the greatest, follow closely by Fe, addition of P showed no effect Effect of P addition varied among different ecosystems. In polluted areas, show negative effect Also, in river, stream and lake, NPP increase with P concentration.

27. 9.4 Primary production varies among ecosystems Patterns of productivity reflect global patterns of temperature and precipitation. High NPP in equatorial zone and coastal region.

29. Geographic variation in primary productivity of world’s oceans • Great transport of nutrient from bottom to top • Nutrient from terrestrial ecosystems High productivity is along coastal regions

32. 9.5 Only 5%– 20% of assimilated energy passes between trophic levels • Net primary production is the energy available to the heterotrophic component of the ecosystem • Either herbivores or decomposers eventually consume all plant productivity, but often it is not all used within the same ecosystem. • Secondary production: net energy of production of secondary consumers • Energy stored in plant material, once consumed, some passes through the body as waste products. • Of the energy assimilated, part is used as heat for metabolism (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

33. Relationship of Secondary production and primary production Secondary production depends on primary production for energy Sam McNaughton (Syracuse Uni.) 69 studies for terrestrial ecosystems (from Arctic tundra to tropical forests)

34. Similar relationship in lake ecosystems 43 lakes+12 reservoirs Tropic to Arctic

35. Energy use is a complex process. Not all consumers have the same efficiency A simple model of energy flow through consumer I: food ingested by a consumer A: a portion is assimilated across the gut wall, convert nutrient to body biomass (digestion, absorption) W: remainder is expelled from the body as waste products (egested energy) R: of the energy assimilated, part is used for respiration (respired energy) E: animal excrete small portion as nitrogen-containing compounds (as ammonia, urea, uric acid) (excreted energy) P: remainder goes to production (new growth and reproduction)

37. Based on these data, we can calculate: Assimilation efficiency A/I, ratio of assimilation to ingestion measure the efficiency with which consumer extracts energy from food Secondary consumers: 60-90% Production efficiency P/A, ratio of production to assimilation measure the efficiency with which the consumer incorporates assimilated energy into secondary production. Homoeothermic: low, 1 % (birds) -6% (small mammals) Poikilotherimic: high, as much as 75%.

38. Secondary producers are not necessarily highly efficient

39. Energy flow through tropic levels can be quantified Energy flow within a single trophic compartment Consumption efficiency: In/Pn-1 Ecological efficiency (food chair efficiency) 14/200=7%

41. Production efficiency varies mainly according to taxonomic class Endotherms have low P/A Invertebrates have high P/A Vertebrates: ectotherms have intermediate

42. 9.6 Ecosystem have two major food chains Food chain is a flow of energy Feeding relationships within a food chain are defined in terms of trophic or consumer level 1st level: Autotrophs or primary producer 2nd level: herbivores (1st level consumers) Higher level: carnivores (2nd level consumers) Some consumers occupy more than one trophic level: omnivores.

43. Within any ecosystem, there are two major food chains Difference 1. Source of energy for herbivores 2. Energy flow direction 3. interconnected

44. 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.

46. 9.7 Energy decreases in each successive trophic level

47. Energy pyramid