ENERGY FLOW IN ECOSYSTEMS • All organisms require energy: for growth, maintenance, reproduction, locomotion, etc • Hence, for all organisms there must be:  A source of energy  A loss of usable energy Types of energy heat energy mechanical energy (+gravitational energy, etc.) chemical energy = energy stored in molecular bonds The distribution of sola radiation energy in the biosphere 0.8% 0.2% Heating air, land, ocean Evaporation 30.0% 46.0% Reflection Photosynthesis 23.0% Wave, wind This pattern of energy flow among different organisms is the TROPHIC STRUCTURE of an ecosystem Transformations of energy The transformations of energy from solar radiation to chemical energy and mechanical energy and finally back to heat of Ecosystem Ecology Energy and biomass pyramids The concepts • PG: Gross primary productivity – = the total rate of photosynthesis – = the rate of energy capture by producers (kcal/m2/yr) – = the amount of new biomass of producers (g/m2/yr) • PN = PG – R; Net primary production is thus the amount of energy stored by the producers and potentially available to consumers and decomposers • B: Standing crop Biomass – the amount of accumulated organic matter found in an area at a given time The concepts • NU: Not consumed • NA: Undigested / Fecal wastes • R: Respiration • P: Secondary productivity – the rate of production of new biomass by consumers, – the rate at which consumers convert organic material into new biomass of consumers The common method of measuring PN  Terrestrial ecosystems  To estimate the change in Standing crop Biomass over a given time interval (t2 –t1)  B = B(t2) – B(t1)  PN = B + D + C  D: loss of biomass due to the dead of plants from t1 to t2  C: loss of biomass due to consumption by consumer Primary production varies with time Net primary production (NPP) and standing biomass allocation for a 90-year-old Michigan forest estimated from inventory-based methods in which biomass growth is quantified over time (Gough et al 2008) Primary productivity limits secondary production Net primary productivity (kJ/m2/yr) Primary productivity limits secondary production  Trophic efficency (TE): the ratio of productivity in a given trophic levelGrowth (Pn) to trophic level it feeds on (Pn-1Respiration ) 33J Undigested 100J 67J (P) TE = Pn / Pn-1  Growth efficency: the ratio of energy for growth to total energy 200J (A) Growth efficency (P/A) = 33/200 = 16,5% Production efficiency (x100) of various animal group (Humphrey, 1979) Group P/A (%) Group P/A (%) Mice 4.10 Orthoptera 41.67 Voles 2.63 Hemiptera 41.90 Other mammals 2.92 All other insects 41.23 Birds 1.26 Mollusca 21.59 Fish 9.74 Crustacea 24.96 8.31 All other noninsect invertebrates 27.68 Social insects General patterns of energy flow through ecosystems (Begon et al, 1986) FOREST Respiration Respiration GRAZER SYSTEM DECOMPOSER SYSTEM NET PRIMARY PRODUCTIVITY DEAD ORGANIC MATTER General patterns of energy flow through ecosystems (Begon et al, 1986) GRASSLAND Respiration Respiration GRAZER SYSTEM DECOMPOSER SYSTEM NET PRIMARY PRODUCTIVITY DEAD ORGANIC MATTER General patterns of energy flow through ecosystems (Begon et al, 1986) PHYTOPLANKTON COMMUNITY Respiration Respiration GRAZER SYSTEM DECOMPOSER SYSTEM NET PRIMARY PRODUCTIVITY DEAD ORGANIC MATTER General patterns of energy flow through ecosystems (Begon et al, 1986) STREAM COMMUNITY Respiration Respiration GRAZER SYSTEM DECOMPOSER SYSTEM NET PRIMARY PRODUCTIVITY DEAD ORGANIC MATTER From terrestrial catchment The net primary productivity of biomes Estuaries Swamps and marshes Tropical rain forest Temperate forest Northern coniferous forest (taiga) Savanna Agricultural land Woodland and shrubland Temperate grassland Lakes and streams Continental shelf Open ocean Tundra (arctic and alpine) Desert scrub Extreme desert 800 1,600 2,400 3,200 4,000 4,800 5,600 6,400 7,200 Average net primary productivity (kcal/m2/yr) 8,000 8,800 9,600 Net primary productivity (kgC/m2/năm) www.sage.wisc.edu Annual rainfall (cm) 300 P: 10 - 50 B: 250 - 400 Primary Productivity and Biomass (ton/ha) 200 P: 3,5 - 10 B: 70 - 250 100 P: 3,5 - B: - 35 P: - B: - 18 P: - 2,5 B: - 30 20 P: - 20 B: 25 - 70 10 Avegare temperature(OC) P: 0,1 - B: -10 ...Types of energy heat energy mechanical energy (+gravitational energy, etc.) chemical energy = energy stored in molecular bonds The distribution of sola radiation energy in the biosphere... of measuring PN  Aquatic ecosystems  To estimate the change in O2 concentration in light/dark bottle  Water sample containing phytoplankton O2 produced by photosynthesis O2 consumed in respiration... photosynthesis O2 consumed in respiration Limiting Factors control PN in Terrestrial ecosystems Limiting Factors control PN in Aquatic ecosystems 100 12 10 PN 10 Light intensity (% of suface value) 50 0