Applications of Systems Ecology to Site Design? Some principles of systems modeling Dr. David Blersch Biosystems Engineering Department Auburn University [email protected] 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 of development in ecological design An ocean food web n How do we conceptualize a system this complex? # of Nodes # of Path # of Possible Connections 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 Systems Ecology Species interactions Energetics Distribution patterns Nutrient cycling Reductionist 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. Nutrients Energy Storage Source Structure Production Export Organic X Matter System boundary Depreciation Used energy Nutrients Consumer Phytoplankton Zooplank -ton Q P R Fish MacrophyPtes k2 R k Macro- Producer 1 invertebr Sun ates Benthic Algae Organic Matter Storage Interaction Principle 1: Ecosystems are hierarchical. P Principle 2: Production and consumption are linked by feedback. C Principle 3: Ecosystems organize such that P:C → 1 Time The systems description of ecosystems show us that ecosystems are… Complex & Emergent Nonlinear & Stochastic Nutrients Organic Matter System boundary E P Z S F Nutrients Phytoplankton Zooplank -ton Fish Macrophytes Macro- invertebr Sun ates dP/dt = k EP – k P – k PZ Benthic Algae Organic 1 2 3 Matter dZ/dt = k4PZ – k5S – k6ZS Key dS/dt = k7ZS – k8S – k9SF dF/dt = k10SF – k11F # of # of Paths # of Possible Nodes Paths Consumer arrangements 3 3 6 5 10 120 6 Producer 10 45 3.63 x 10 25 297 1.55 x 1025 Storage Interaction Where does modeling fit in building knowledge? Geradin (1968) Models of Ecosystem Development n Describes the expected trajectory of ecological development along an environmental gradient. n Continuum models n Threshold models n Staged threshold models Gradual Continuum model Native, normal function n Ecosystem responds in continuous manner to Restoration & environmental change. Design State State n Strong internal Impairment Ecosystem Ecosystem regulation because of Exotic, degraded feedback function Environmental Condition Suding & Hobbs (2009) Threshold Model Native, normal n Ecosystem responds function non-linearly n A small change in the Restoration & environmental variable Design can produce abrupt State Impairment Ecosystem Ecosystem changes in ecosystem Exotic, degraded state function Environmental Condition Suding & Hobbs (2009) Alternative Stable States: Initially very resilient to change Hysteresis Threshold Model Native, normal function n Ecosystem responds non-linearly Impairment Restoration State State n Exotic state is resilient: Design Return pathway to Ecosystem Exotic, former state is different degraded function Environmental Condition Suding & Hobbs (2009) Staged Threshold Model Biotic Abiotic Native, Threshold Threshold normal function 1 n Ecosystem responds 2 non-linearly Impairment Restoration 3 n Biotic and abiotic Design State State 4 thresholds may be a Ecosystem Restoration 5 Design Exotic, barrier to restoration or degraded design 6 function Environmental Condition Suding & Hobbs (2009) E.g., Physical modification must precede biotic manipulation How can we know if these models apply? n Look for feedback Turbidity relationships in the system that might affect the dynamics. Vegetation Causal Relationships model E.g. Shallow Lake + Turbidity + Sediment Algae Resuspension - Water + + + - - Depth - Vegetation - Nutrients - + Waves Allelopathy - Fish - Zooplankton A chain of pathways is multiplicative Carpenter & Scheffer (2009) Systems principles for ecological design n What are the important feedback components in your system? n What are the dynamics of your system? n Continuum? Threshold? Stochastic? How can you tell? n Observational time series analysis: follow state variables and degradation pathway n Manipulative experiments: Do replicate plots diverge over time? Outcomes Null Hypothesis: There is no threshold effect Type 1 Error: Fail to reject the Type 2 Error: Reject the true false null hypothesis null hypothesis No threshold Threshold accounted for accounted for when when it exists it does not exist Ecosystem Wasted does not Resources develop 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 of 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. .