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

Systems Ecology

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

Food Web

Community Matrix

Biogeochemical Cycles

Ecological Pyramids (numbers, biomass, and energy Pyramid 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

At equilibrium (d  i /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 = = = = = 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 % 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 _________________________________________________________________________ CanopySapling Species (%) Species BTA GB SF BG SG WO OK HI TU RM BE Total ___________________________________________________________________ _______ BT Aspen Gray birch Sassafras Blackgum Sweetgum White Oak Red Oak Hickory Tuliptree Red Maple Beech __________________________________________________________________________ BTA in next generation = 0.03 BTA SF 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 __________________________________________________________________ __________________ Predicted climax __________________________________________________________________ __________________

Evolutionary Convergence and Ecological Equivalence