Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels IV. Succession A. Definitions - succession: a change in community composition through time

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels IV. Succession A. Definitions - succession: a change in community composition through time - sere: a particular stage or sequence

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels IV. Succession A. Definitions - succession: a change in community composition through time - sere: a particular stage or sequence - pioneer: first community

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels IV. Succession A. Definitions - succession: a change in community composition through time - sere: a particular stage or sequence - pioneer: first community - climax: self-replacing community

B. Classifying Vegetative Communities 1. Focus on the Climax Clements’ view of the climax as a ‘closed, mature, developmental state,’ dependent solely on climate. In North America, he recognized only 9 climax community types: 2 grasslands (prairie, tundra) 3 scrub (sagebrush, desert, chaparral) 9 forests

B. Classifying Vegetative Communities 1. Focus on the Climax Curtis and McIntosh: ‘Continuum’ index

B. Classifying Vegetative Communities 1. Focus on the Climax Whittaker’s view: ‘Dominance’ classification Red oak Sugar maple

B. Classifying Vegetative Communities 1. Focus on the Climax 2. Classification by Indicator Species Braun-Blanquet method of vegetative classification: Based on whole floristic surveys and the identification of ‘indicator’ taxa – typically neither dominants nor extremely rare species. 440 vegetation types in South Africa.

B. Classifying Vegetative Communities 1. Focus on the Climax 2. Classification by Indicator Species Vegetation Types of California Jennings, et al. 2009. Standards for associations and alliances of the U.S. National Vegetation Classification. Ecological Monographs 79:173-199.

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels IV. Succession A. Definitions B. Classifying Vegetative Communities C. Types of Succession

1. Primary succession: on previously unvegetated substrate or ‘devoid of life’

1. Primary succession: on previously unvegetated substrate or ‘devoid of life’

1. Primary succession: on previously unvegetated substrate or ‘devoid of life’

1. Primary succession: on previously unvegetated substrate or ‘devoid of life’

1. Primary succession: on previously unvegetated substrate or ‘devoid of life’

2. Secondary Succession: follows a disturbance (removes biomass)

3. Disturbance-mediated Succession Fire, grazers, predators, etc.

3. Disturbance-mediated Succession The effect of the disturbance depends on its intensity and size. Small, low intensity disturbance: One tree and a few plants underneath die. Small canopy gap is quickly filled by neighboring trees in the understory; recovery by individual growth.

3. Disturbance-mediated Succession The effect of the disturbance depends on its intensity and size. Large, high intensity disturbance: Entire canopy gone; many species driven to local extinction. Recovery by colonization.

These effects are really true of most successional seres, not just disturbance-mediated succession.

4. Heterotrophic succession

4. Heterotrophic succession Eberhardt, TL and DA Elliot. 2007.A preliminary investigation of insect colonisation and succession on remains in New Zealand. Forensic Science International 176:217-223.

4. Heterotrophic succession no yes

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels IV. Succession A. Definitions B. Classifying Vegetative Communities C. Types of Succession D. Mechanisms - facilitation, tolerance, and inhibition

examples: colonization of bare rock: lichens, moss, herbs; Facilitated: early species change environment and increase the probability of successful colonization by later species. examples: colonization of bare rock: lichens, moss, herbs; colonization of carcasses: beetles, flies, etc. Effects of wildebeest Aspen fix nitrogen that helps nitrogen-limited trees colonize

Tolerance: Tolerance: early species have no effect on later species. This occurs if there is 'ecological equivalence' among the species. Many stages in later forest succession seem dominated by this mechanism. Also, later species tolerate early species... so shade tolerant species come to dominate because they tolerate the shade of early species, but inhibit those early species with their own shade.

Inhibition: Early species retard the colonization success of later species. If these effects vary among early species, there can be "priority effects". The species that gets there first has a differential and deterministic effect on the subsequent structure of the community. Important where allelopathic interactions occur. Bryozoans block colonization of tunicates and sponges.

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels IV. Succession A. Definitions B. Classifying Vegetative Communities C. Types of Succession D. Mechanisms - facilitation, tolerance, and inhibition E. Invasive Species

“Invasive species” are facilitated or tolerated by natives, and subsequently inhibit them. Often they have escaped their predators or pathogens, and are ‘tolerated’ by native predators/pathogens…thus escaping limitation and increasing to densities where they compete with natives. Here, field plants are affected by transplantation into a different mycorrhizal environment.

F. Modelling Succession: Tilman (1985) A, B B Our old 2-species model with stable coexistence possible.

F. Modelling Succession: Tilman (1985) A, B B If resource supply rates are negatively correlated, then the community may succeed from A to A-B coexistence to B as concentrations change

F. Modelling Succession: Tilman (1985) A, B B B, C C ...and then to B,C and C.... and etc....

F. Modelling Succession: Tilman (1985) A, B B B, C C ...and then to B,C and C.... and etc.... C, D D

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels IV. Succession A. Definitions B. Classifying Vegetative Communities C. Types of Succession D. Mechanisms - facilitation, tolerance, and inhibition E. Invasive Species F. Modelling Succession G. Characteristics of Plants through Succession

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels IV. Succession A. Definitions B. Types C. Mechanisms D. Model – Tilman 1985 E. Community Patterns

E. Community Patterns (From Morin, 1998) Variable Early Late Organism Size small large life history r K Biomass low high Richness, Diversity low high Structural complexity low high Niches broad narrow Nutrient cycles open closed Stability low high trophic relationships linear web-like connectance low high