Applications of Systems Ecology to Site Design? Some principles of - - PowerPoint PPT Presentation

Applications of Systems Ecology to Site Design?

Some principles of systems modeling

• Dr. David Blersch

Biosystems Engineering Department Auburn University dmb0040@auburn.edu

Ecological Design in the Southeast: Workshop and Design Charrette American Ecological Engineering Society Certified Ecological Designer workshop Four Points Sheraton Asheville, NC 23-25 April 2014

Ecosystem Dynamics

n Understanding systems dynamics is

important for predicting the trajectory

• f development in ecological design

An ocean food web

n How do we

conceptualize a system this complex?

# of Nodes # of Path Connections # of Possible Path Arrangements

3 3 6 5 10 120 10 45 3.63 x 106 25 297 1.55 x 1025

What is an ecosystem?

n Classic description: A dynamic set of living organisms (plants, animals

and microorganisms) all interacting among themselves and with the environment in which they live (soil, climate, water, and light).

n “Feedback” description: An organized system of land, water, mineral

cycles, living organisms, and their programmatic behavioral control mechanisms (Odum 1994).

Population Ecology Species interactions Distribution patterns Reductionist Systems Ecology Energetics Nutrient cycling Holistic

How do we understand an ecosystem?

Modeling Elements

• Boundary conditions
• Forcing functions
• State Variables
• Relationships:
• Equations
• Parameters
• Constants
• Conservation laws

Production and consumption are linked by feedback relationships.

All living systems are autocatalytic.

X

Consumer

P R

Producer Storage Interaction

k1 k2 Q

System boundary Sun

Organic Matter

Nutrients

Nutrients Phytoplankton Macrophytes Benthic Algae

Organic Matter

Zooplank

• ton

Macro- invertebr ates Fish

Principle 3: Ecosystems organize such that P:C → 1

P R

Time

P C

Principle 2: Production and consumption are linked by feedback. Principle 1: Ecosystems are hierarchical.

The systems description of ecosystems show us that ecosystems are…

P

Z S F

E

System boundary Sun

• ton

# of Nodes # of Paths # of Possible Paths arrangements 3 3 6 5 10 120 10 45 3.63 x 106 25 297 1.55 x 1025

Consumer Producer Storage Interaction

Key

Complex & Emergent Nonlinear & Stochastic

dP/dt = k1EP – k2P – k3PZ dZ/dt = k4PZ – k5S – k6ZS dS/dt = k7ZS – k8S – k9SF dF/dt = k10SF – k11F

Where does modeling fit in building knowledge?

Geradin (1968)

Models of Ecosystem Development

n Describes the expected trajectory

• f ecological development along an

environmental gradient.

n Continuum models n Threshold models n Staged threshold models

Gradual Continuum model

n Ecosystem responds in

continuous manner to environmental change.

n Strong internal

regulation because of feedback

Ecosystem State Environmental Condition

Native, normal function Exotic, degraded function Impairment Restoration & Design Suding & Hobbs (2009)

Threshold Model

n Ecosystem responds

non-linearly

n A small change in the

environmental variable can produce abrupt changes in ecosystem state

Ecosystem State Environmental Condition

Native, normal function Exotic, degraded function Impairment Restoration & Design

Alternative Stable States: Initially very resilient to change

Suding & Hobbs (2009)

Hysteresis Threshold Model

n Ecosystem responds

non-linearly

n Exotic state is resilient:

Return pathway to former state is different

Ecosystem State Environmental Condition

Native, normal function Exotic, degraded function Impairment Restoration Design Suding & Hobbs (2009)

Staged Threshold Model

n Ecosystem responds

non-linearly

n Biotic and abiotic

thresholds may be a barrier to restoration or design

Ecosystem State

Environmental Condition

Native, normal function Exotic, degraded function Impairment Restoration Design 5 6 3 4 1 2 Restoration Design Biotic Threshold Abiotic Threshold

E.g., Physical modification must precede biotic manipulation

Suding & Hobbs (2009)

How can we know if these models apply?

n Look for feedback

relationships in the system that might affect the dynamics.

Turbidity Vegetation

Causal Relationships model

Vegetation Turbidity

• Algae

+

Sediment Resuspension

+

Nutrients

+

• Waves

+

• Water

Depth

• Allelopathy
• +

Fish Zooplankton

+

• A chain of pathways is multiplicative

E.g. Shallow Lake

Carpenter & Scheffer (2009)

n What are the important feedback

components in your system?

n What are the dynamics of your

system?

n Continuum? Threshold?

Stochastic? Systems principles for ecological design

How can you tell?

n Observational time series

analysis: follow state variables and degradation pathway

n Manipulative experiments:

Do replicate plots diverge

• ver time?

Outcomes

Type 1 Error: Fail to reject the false null hypothesis Type 2 Error: Reject the true null hypothesis

Null Hypothesis: There is no threshold effect

No threshold accounted for when it exists Ecosystem does not develop Threshold accounted for when it does not exist Wasted Resources

Best Approach: Adopt strategies that are effective in most scenarios based on real-time monitoring of dynamics. Be adaptive.

Summary

n Understanding systems dynamics is

important for predicting the trajectory

• f development in ecological design.

n Ecosystem conceptualization is key for

identifying possible systems dynamics.

n Conceptualization and physical

investigation are necessary to look for + and – feedbacks, threshold limits, and dynamic relationships.

References and More Material

Breckling, B., Jopp, F., Reuter, H. 2011. Ordinary differential equations. In:

• F. Jopp, et al. (eds.) Modelling Complex Ecological Dynamics. Springer-

Verlag, Berlin, Heidelberg. Jorgensen, S.E., and G. Bendoricchio. 2001. Fundamentals of Ecological Modelling (3rd Edition). Elsevier Science, New York. Kangas, P.C. 2004. Ecological Engineering: Principles and Practice. Lewis Publishers, Boca Raton, Florida. Odum, H.T. 1994. Ecological and General Systems: An Introduction to Systems Ecology. University Press of Colorado, Niwot, Colorado. Odum, H.T., and E.C. Odum. 2000. Modeling for All Scales: An Introduction to System Simulation. Academic Press, San Diego, California. Suding, K.N., and R.J. Hobbs. 2009. Models of Ecosystem Dynamics as Frameworks for Restoration Ecology. In: R.J. Hobbs and K.N. Suding (eds.). New Models for Ecosystem Dynamics and Restoration. SER International, Island Press, Washington, DC.