ECOSYSTEM DYNAMICS

KGA172 Space, Place and NaturePresented by Associate Professor Elaine StratfordSemester 2

LOOKING BACK, LOOKING FORWARD

Part 1

Revising Lecture 2.21. Define ecosystem. Explain its etymology. In

terms of helping us understand nature, why might it matter that ecosystem has the same origins [derivation] as household – from the Greek oikos?

2. How does Eugene Odum specifically describe ecology and in what ways is the idea of exchange important in that description?

3. What is meant by ‘open system’ in relation to ecosystems? Can you draw such a system accounting for abiotic and biotic elements?

4. How would you explain to someone completely unfamiliar with the subject the links between and among biomes, limiting factors and ecotones? Give examples.

5. What are the main distinctions between gross and net primary production? What are the main determinants of those distinctions?

6. Describe in fulsome detail the components and relationships one might find along a terrestrial and an aquatic food chain. What do food chains reveal about ecosystems as integrated phenomena?

Auguste Rodin, A man thinking

Learning ObjectivesModule 2 Lecture 3• Be able to

– describe and explain• interactions between

species• the meaning of the

concepts of disturbance and succession

– describe and critique • classical succession theory• contemporary

understanding of vegetation dynamics

– make links between these ideas and the larger question of how we understand nature

KGA172• Know and be able to (a) employ basic

geographical terminology and concepts, (b) find, evaluate, analyse and reference appropriate literature, (c) contribute to debates about development and sustainability

• Comprehend and be able to explain spatial patterns, generate basic maps, field sketches and graphs, and communicate in written and graphical forms

• Apply key academic skills and (a) engage in critical thinking, discussion and listening, and in self-reflection and reflection upon the viewpoints of others and (b) research, plan and conduct fieldwork to collect data

• Analyse and interpret basic spatial, numerical and qualitative information

• Synthesize and integrate knowledge of social and Earth systems

Textbook Reading Continue to mine Bergman and Renwick (2008)

Critical reading1.What is the author’s purpose?2.What key questions or problems does the author raise?3.What information, data and evidence does the author present?4.What key concepts does the author use to organize this information, this evidence?5.What key conclusions is the author coming to? Are those conclusions justified? 6.What are the author’s primary assumptions?7.What viewpoints is the author writing from?8.What are the implications of the author’s reasoning?[from Foundation for Critical Thinking]

A man in a library

INTERACTIONPart 2

Basic Types of 2-species interaction

Interaction Species 1 Species 2Neutral 0 0

Competition _ _

Consumption + _

Commensalism + 0

Mutualism + +

Competition

Consumption

Commensalism

Mutualism

COMPETITIONPart 3

Exploitative Competition

Competition for light, water and nutrients

(Greg Unwin)

Competition for light

R.E. Ricklefs (1990) Ecology. 3rd ed. Freeman & Co.

Competition for carbohydrates and/or protein

Single visits to flowers by bumblebees resulted in less than 10% as many seeds as did single visits by swift parrots

Hingston et al. (2004) Australian Journal of Botany 52, 371-379

Pre-emptive competition Dominance: first grab on resources

(Chris Servheen)

Overgrowth competition pre-emptive competition for light (+ other resources)

(Greg Unwin)

Interference competition- chemical interference (allelopathy)

(facultyengineering.ucdavis.edu)

(R.E. Ricklefs (1990) Ecology. 3rd ed. Freeman & Co.)

Territorial interference

(science.howstuffworks.com) (www.wolaver.org)

Principle of competitive exclusion

(Paul Colinvaux (1993) Ecology 2. Wiley).

CONSUMPTIONPart 4

• predators kill prey, usually smaller than themselves

• parasites feed off other organisms, usually larger than themselves, usually without killing them

• grazers and browsers eat part or all of primary consumers

• consumers can reduce populations to below carrying capacity

Predation, parasitism and grazing

(Ricklefs, 1990, Ecology)

(Colinvaux, 1993, Ecology 2)

Consumer-prey relationships can result in sharp population fluctuations

COMMENSALISM AND MUTUALISMPart 5

Commensalism

(www.tas.gov.au)

www.thefishsite.com

Mutualism (symbiosis)• fungal (mycorrhizal fungi, lichen)

• bacterial (nitrogen-fixing)

• pollination and co-evolution

• facilitation of predation of parasites or grazers

• the dangers of specific interdependence

(P. and E. Grey (2001) Fungi down under

(www.anu.edu.au) (www.myrmecos.net)

DISTURBANCE AND SUCCESSIONPart 6

Disturbance – an environmental event (or events) that results in a change in biomass or the resources that support species at a rate

that is faster than normal changeExogenous [external] disturbance … allogenic disturbance response

Endogenous [internal] disturbance … autogenic succession response

Exogenous or endogenous?

Fire – exogenous and endogenous disturbance

(Greg Unwin)

Colinvaux Ecology 2

Traditional succession theory (Clements and Tansley)

Edaphic and flood disclimax

Primary and secondary succession

(G L Unwin)

Relay floristics

(Bowman Australian Rainforests

(Greg Unwin)

Cyclic succession

(Greg Unwin)

(Colinvaux Ecology 2)

Some theoretical generalisationsRuderals (R strategists) to Competitors to

Stress tolerators (K strategists)

(Colinvaux Ecology 2)

Productivity trends during succession