Community and Ecosystem EcologyMacrodescriptors = 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

Systems Ecology

Compartmentation Trophic Levels

Autotrophs = producers Heterotrophs = consumers & decomposersPrimary carnivores = secondary consumersSecondary carnivores = tertiary consumersTrophic continuumHorizontal versus vertical interactionsWithin and between trophic levels

Guild StructureFoliage gleaning insectivorous birds

Food WebsSubwebs, sink vs. source food websConnectance

Food Web

Community Matrix

Biogeochemical Cycles

Ecological Pyramids (numbers, biomass, and energyPyramid of energy

Measures of standing crop versus rates of flow

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, , with a subscript to indicate the appropriate trophic level: 1 = primary producers, 2 = herbivores, 3 = primary carnivores, and so on. Similarly, the rate of flow of energy between trophic levels is designated by lower case lambdas, ij , 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.

Energy Flow and Ecological Energetics

Energy Flow and Ecological Energetics

At equilibrium (di/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):

10 = 01 + 02 + 03 + 04

10 = 21 + 01 + 41

21 = 32 + 02 + 42

32 = 03 + 43

41 + 42 + 43 = 04

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

Secondary Succession

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 104Gray birch - - 47 12 8 2 8 0 3 17 3 837Sassafras 3 1 10 3 6 3 10 12 - 37 15 68Blackgum 1 1 3 20 9 1 7 6 10 25 17 80Sweetgum - - 16 0 31 0 7 7 5 27 7 662White Oak - - 6 7 4 10 7 3 14 32 17 71Red Oak - - 2 11 7 6 8 8 8 33 17 266Hickory - - 1 3 1 3 13 4 9 49 17 223Tuliptree - - 2 4 4 - 11 7 9 29 34 81Red Maple - - 13 10 9 2 8 19 3 13 23 489Beech - - - 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

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__________________________________________________________________ __________________

Evolutionary Convergence and Ecological Equivalence