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Systems Ecology

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Systems Ecology

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  1. Community and Ecosystem Ecology Macrodescriptors = Aggregate Variables Trophic structure, food webs, connectance rates of energy fixation and flow, ecological efficiency diversity, stability, relative importance curves guild structure, successional stages Communities are not designed by natural selection for smooth and efficient function, but are composed of many antagonists (we need to attempt to understand them in terms of interactions between individual organisms

  2. Systems Ecology

  3. Compartmentation Trophic Levels Autotrophs = producers Heterotrophs = consumers & decomposers Primary carnivores = secondary consumers Secondary carnivores = tertiary consumers Trophic continuum Horizontal versus vertical interactions Within and between trophic levels Guild Structure Foliage gleaning insectivorous birds Food Webs Subwebs, sink vs. source food webs Connectance

  4. Food Web

  5. Community Matrix

  6. Biogeochemical Cycles

  7. Ecological Pyramids (numbers, biomass, and energy Pyramid of energy Measures of standing crop versus rates of flow

  8. Energy Flow and Ecological Energetics The energy content of a trophic level at any instant (i.e., its standing crop in energy) is usually represented by capital lambda, L, with a subscript to indicate the appropriate trophic level: L1 = primary producers, L2 = herbivores, L3 = primary carnivores, and so on. Similarly, the rate of flow of energy between trophic levels is designated by lower case lambdas, lij , where the i and j subscripts indicate the two trophic levels involved with i representing the level receiving and j the level losing energy. Subscripts of zero denote the world external to the system; subscripts of 1, 2, 3, and so on, indicate trophic level as previously stated.

  9. Energy Flow and Ecological Energetics

  10. Energy Flow and Ecological Energetics At equilibrium (dLi/dt = 0 for all i), energy flow in the system portrayed in the figure may thus be represented by a set of simple equations (with inputs on the left and rate of outflow to the right of the equal signs): l10 = l01 + l02 + l03 + l04 l10 = l21 + l01 + l41 l21 = l32 + l02 + l42 l32 = l03 + l43 l41 + l42 + l43 = l04

  11. Energy Flow and Ecological Energetics Gross Productivity Gross annual production (GAP) Net productivity Net annual production (NAP) Respiration in tropical rainforest 75-80% of GAP Respiration in temperate forests 50-75% of GAP In most other communities, it is 25-50 % of GAP Only about 5-10% of plant food is harvested by animals Remainder of NAP is consumed by decomposers

  12. Secondary Succession

  13. Transition Matrix for Institute Woods in Princeton _________________________________________________________________________ Canopy Sapling Species (%) Species BTA GB SF BG SG WO OK HI TU RM BE Total __________________________________________________________________________ BT Aspen 3 5 9 6 6 - 2 4 2 60 3 104 Gray birch - - 47 12 8 2 8 0 3 17 3 837 Sassafras 3 1 10 3 6 3 10 12 - 37 15 68 Blackgum 1 1 3 20 9 1 7 6 10 25 17 80 Sweetgum - - 16 0 31 0 7 7 5 27 7 662 White Oak - - 6 7 4 10 7 3 14 32 17 71 Red Oak - - 2 11 7 6 8 8 8 33 17 266 Hickory - - 1 3 1 3 13 4 9 49 17 223 Tuliptree - - 2 4 4 - 11 7 9 29 34 81 Red Maple - - 13 10 9 2 8 19 3 13 23 489 Beech - - - 2 1 1 1 1 8 6 80 405 __________________________________________________________________________ BTA in next generation = 0.03 BTA + 0.03 SF + 0.01 BG . Grand Total = 3286

  14. Distributions of Trees Observed in 4 Forests and Predicted Climax __________________________________________________________________ __________________ Age (years) BTA GB SF BG SG WO OK HI TU RM BE __________________________________________________________________ __________________ 25 0 49 2 7 18 0 3 0 0 20 1 65 26 6 0 45 0 0 12 1 4 6 0 150 - - 0 1 5 0 22 0 0 70 2 350 - - - 6 - 3 - 0 14 1 76 Predicted climax 0 0 2 3 4 2 4 6 6 10 63 __________________________________________________________________ __________________

  15. Evolutionary Convergence and Ecological Equivalence

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