Patterns in ecosystems can be confusing; they can be observed over many different spatial and time scales. All species assemblages have the same underlying rules regulating their pattern or structure (The Architecture of Complexity, Simon, 1962). Complex ecosystems are not controlled by a central or linear function but are characterized by non-linear feedback loops, demonstrating indirect effects from an action. (Li Bai-Lan, 2007). Feedback occurs when a signal leaves one component and returns to the original component after passing through one or more other components in the system. If the signs of the output and input signals are the same (either both positive or both negative), then it is a positive feedback loop. If the signs of the output and input signals are opposite, then it is a negative feedback loop (Feedback in the Plant Soil System by Ehrenfield, J. G., Ravit, B. and Elgersma, K.).

Effects that occur as a result of a change in a component that is not immediately connected to the original component (two or more links separate the two components) are called indirect effects.  Take a closer look at:

  • Disturbance is an important factor in ecosystems in creating patterns. Check out Wildfires, complexity, and highly optimized tolerance by Monitz, M. A., Morais, M. E., Summerell, L. A., Carlson, J. M., and Doyle, J. 
  • Food Webs and Models. Food webs show the linkages between species and the environment. Read this powerpoint presentation about foodwebs to learn more.

Conceptual modeling based upon field based ecological research can be useful to illustrate some aspects of complex natural system functioning such as feedback, indirect effects, and foodweb structure (A spatially explicit hierarchical approach to modeling by Wu, J. and David, J. L.).

Other relevant Journal Articles:

  • Are there general laws in Ecology? by Lawton, J. H.
Abiotic Factors: