1 / 23

Energy Flow in an old field, MI:

Energy Flow in an old field, MI:. Sun. 47.1 x 10 8 kcal/ha/yr strikes plants. 58.3 x 10 6 kcal/ha/yr assimilated by plants or only 1.2 % of available energy. = Gross Primary Productivity : total energy captured or assimilated for metabolism and growth of new tissue.

bcasteel
Download Presentation

Energy Flow in an old field, MI:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Energy Flow in an old field, MI: Sun 47.1 x 108 kcal/ha/yr strikes plants 58.3 x 106 kcal/ha/yr assimilated by plants or only 1.2 % of available energy = Gross Primary Productivity: total energy captured or assimilated for metabolism and growth of new tissue Assimilation Efficiency: how well an organism assimilates available (ingested or consumed) energy An/In = 1.2 % for plants above 58.3 x 106 47.1 x 108

  2. Of Gross Primary Productivity, plants use 15 % for respiration and 85 % (49.5 x 106 kcal/ha/yr)for new tissue growth Net Primary Productivity: amount of energy assimilated that is used for new tissue growth by plants Production Efficiency: how well energy is used for net production from amount assimilated Pn/An = 85 % for plants 49.5 x 106 58.3 x 106

  3. Of NPP, only 32 % (15.8 x 106 kcal/ha/yr) is edible tissue available for herbivores to ingest or consume Mice only consume 250 x 103 of this edible tissue (1.6 %) or only 0.5 % of NPP (49.5 x 106) Consumption Efficiency: amount of net production that is ingested or consumed by the next level up In/Pn-1 = 0.5 % in mice 250 x 103 49.5 x 106

  4. Of the energy consumed by the mice (250 x 103 kcal), 68 % used for respiration 30 % lost (feces and undigested material 2 % (5170 kg) used for net secondary productivity Weasels at third trophic level consume mice, only 2.2 % of this energy goes into net tertiary productivity This last amount is only 0.00026 % of the original NPP (49.5 x 106 kcal) produced by plants!

  5. These efficiencies will vary by trophic level e.g., carnivores can absorb their food better than herbivores Thus, AE is much higher in carnivores Herbivores have low AE—plant matter is difficult to digest Also, ectotherms have higher PE than endotherms --they don’t need to maintain constant Tb

  6. 10 % Rule A general rule in ecology that only 10 % of energy on average is transferred from one trophic level up to the next level This means that ~ 90 % of energy is lost, not digestible and left behind

  7. Logical Assumptions for Energy Flow A high NPP at first trophic level should allow for more trophic levels in the entire community Any trophic level with high productivity should have more levels above it There should be a threshold value of productivity above which no more trophic levels can be supported

  8. Thus, first assumption that more NPP means more trophic levels above is false!

  9. Phytoplankton Zooplankton Zooplankton Zooplankton Fish Fish

  10. Does any level with relatively high productivity have more levels above it? Ectotherm vs. endotherm communities Ectotherms have higher PE, so should have more levels above them Ecotherms: mean .583 levels above Endotherms: mean .625 levels Prediction #2 is false

  11. Threshold value for more levels above? All but one (14) have 3-4 trophic levels Herbivore Biomass NPP

  12. Quiz • What is the difference between a biomass vs net productivity trophic pyramid? • What is the difference in net vs gross productivity and how do you quantify energy flow in a food chain? • What is the 10% rule in trophic systems? • What are three logical assumptions regarding energy flow up the food chain? • What is the relationship between NPP and herbivore biomass?

  13. What other factors might control the number of trophic levels in a community? Ecological stability: how well a community maintains its structure following a disturbance -- assessed by complexity (links in food web) -- measured by persistence, or how well it retains species richness -- and by resilience, or how quickly a it returns to equilibrium

  14. Phytoplankton Zooplankton Zooplankton Zooplankton Fish Fish Also, center of ocean basin has very low NPP, but high number of trophic levels

  15. Takimoto et al. 2008

  16. Detritivores in 1 m2 of temperate forest soil: ~ 1000 species, millions of individuals 10 million nematodes and protozoa 100,000 springtails and mites 50,000 other invertebrates

  17. Microfauna, < 0.001 mm Mesofauna, 0.001 to 2.0 mm Macrofauna, > 2.0 mm

  18. http://freedesignfile.com/ African savannah herbivores: 1000 kg/km2/yr dead biomass 70-80% consumed by vertebrate detritivores

  19. Feeding Guild A group of species feeding on the same resource in different ways

  20. Quiz • What is meant by stability, connectance, persistence and resilience in ecosystem studies? • What factors are most important in determining the number of trophic levels in an ecosystem? • What is the HSS model and what controls NPP in odd versus even numbered trophic systems? • What are three size classes of detritivores and how do their roles change across different ecosystems? • What is a feeding guild and give an example?

More Related