Subsystems

HT Odum Silver Springs Field Trip  Eoearth.org

This section of the website focuses on specific subsystems within the economy. But first, below, here is a demonstration of the use of diagramming to envision a system.

The Silver Springs ecosystem is an example of a river ecosystem depicted below in simple and more complex energy diagrams (Odum, 1955; Knight, 1980; Brown, 2008; Brown and Ulgiati, 2009). Silver Springs has been studied heavily by researchers at the University of Florida over the years, since it is an active ecosystem interface between man and nature in Ocala, Florida, a short drive from UF. Springs are complex, highly productive, relatively steady-state aquatic ecosystems (Knight & Notestein, 2008). As degradation occurs to our life support system, springs provide a window into anthropogenic impacts.

Most ecosystems have enough features in common to justify describing some basic processes that are common to all. Energy from sunlight is transformed by primary producers, which are then eaten by herbivores (in this case fish), and then by carnivores, and then by top carnivores. An organic storage of detritus is contributed to and used by many species, and the storage is important to all food pathways for recycling. These models depict the energy transformations  in each stage that upgrade some energy, dispersing the rest as heat.

Art by Dr. E.A.McMahan Silver Springs, Ocala, FL 
Odum, Howard T. 1957. Trophic Structure and Productivity of Silver Springs, Florida. Ecological Monographs 27:55–112.
MTBrown 08-In Knight & Notestein http://waterinstitute.ufl.edu/research/projects/downloads/p001-Ch1_SpringsNutrients.pdf
Silver Spring Transformities Brown & Ulgiati 2009
S. Ulgiati, M.T. Brown / Communications in Nonlinear Science and Numerical Simulation 14 (2009) 310–321 

From Brown & Ulgiati (2009) “As energy flows from driving energy sources on the left to higher and higher order ecosystem components, it is transformed from sunlight to plant biomass, to 1st level consumers, to second level and so forth. At each transformation, second law losses decrease the available energy, but the ‘‘quality’’ of energy remaining is increased” (p. 311). “Solar energy drives the system directly (i.e. through photosynthesis) and indirectly through landscape processes that develop aquifer storages, which provide the spring run kinetic energy. Vegetation in the spring run use solar energy and capitalize on the kinetic energy of the spring, which brings a constant supply of nutrients. Products of photosynthesis are consumed directly by herbivores and also deposited in detritus. Herbivores are consumed by carnivores which are, in turn, consumed by top carnivores. With each step in the food-chain, energy is degraded” (Brown & Ulgiati, 2009, p. 314).

S. Ulgiati, M.T. Brown / Communications in Nonlinear Science and Numerical Simulation 14 (2009) 310–321

Losses of complexity in systems due to alterations in driving energies or bioaccumulations of stressors can be examined through network analysis of emergy flows as indicated in the table above, demonstrating loss or alteration of trophic levels.

Martha Odum Radium Springs Georgia

Our civilization can thrive in a future where we live with less