BIOL 4120: Principles of Ecology Lecture 18: Ecosystem Ecology (Energy in the Ecosystem)

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BIOL 4120 Principles of Ecology Lecture 18
Ecosystem Ecology (Energy in the Ecosystem)

• Dafeng Hui
• Office Harned Hall 320
• Phone [phone]
• Email dhui_at_tnstate.edu

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18.4 Primary production varies among ecosystems
Patterns of productivity reflect global patterns
of temperature and precipitation. High NPP in
equatorial zone and coastal region.
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Geographic variation in primary productivity of
worlds oceans

1. Great transport of nutrient from bottom to top
2. Nutrient from terrestrial ecosystems

High productivity is along coastal regions
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18.5 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

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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)
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Similar relationship in lake ecosystems 43
lakes12 reservoirs Tropic to Arctic
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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)
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Based on these data, we can calculate Assimilatio
n 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.
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Secondary producers are not necessarily highly
efficient
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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) 14/2007
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Production efficiency varies mainly according to
taxonomic class Endotherms have low
P/A Invertebrates have high P/A Vertebrates
ectotherms have intermediate