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Carbon cycling and energy flow in ecosystems

The chemical backbone of living things on this planet is carbon. It is the basic building block of sugars, starches, fats, proteins, amino acids, DNA, plant and animal tissues, microorganisms, us and all of our friends (and enemies). In addition to giving life its structural form, carbon based chemicals carry the energy (chemical bonding) that allows living things to survive, grow, and reproduce.

This module contains the basic terminology and some of the fundamental concepts necessary for you to understand in order for you to listen in and maybe even participate in discussions about carbon cycling and energy flow in ecosystems.

Carbon Cycle and Energy Flow

• The capacity or ability to do work
• Heat
• Radiant
• Chemical
• Mechanical
• Electrical
• Exists as
• Potential
• Kenetic

• First Law of Thermodynamics
• Energy cannot be created or destroyed, although it can be transformed from one form to another, for example: radiant to chemical to mechanical.
• Examples
• Second Law of Thermodynamics
• When energy is converted from one form to another, some useful energy is degraded into a lower quality, less useful form -- usually heat. Entropy increases.
• Entropy, or disorder, in a system tends to increase over time.
• Examples

Key Processes in a Patch Scale Carbon Cycle and Energy Folw Pathways

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• Photosynthesis -
• Translocation
• Respiration
• Plant tops
• Plant roots
• Microbial
• Animal
• Leaf, Stem , and Root Death and Litterfall and Root Sloughing
• Decomposition
• Soil Organic Matter Formation
• Herbivory
• Erosion and Harvest
• Run On and Excreta Deposition
• Runoff

The Flow of Energy Through Ecosystems (Unidirectional) - The actors

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• Producers - autotrophs (auto = "self" and tropho = "nourishment")
• Consumers - heterotrophs (heter = "different")
• Primary -- herbivores (plant eaters)
• Secondary -- carnivores (animal eaters), omnivores (plant and animal eaters), detritovores (eat dead stuff)
• Decomposers - Saprophytes (break down organic matter)

• Who Eats Whom?
• Food chains
• Trophic levels
• Food webs
• Ecological Pyramids
• Numbers
• Biomass
• Energy

• Conceptual equation

NPP = GPP - PR where

• Gross primary production (GPP) (Total photosynthesis)
• Net primary productivity (NPP) (Plant growth)
• Plant respiration (PR)
• What controls energy flow and carbon cycling in ecosystems?
• Drivers and feedbacks
• solar radiation
• minerals
• temperature
• & many others
• Internal feedbacks
• Variation in productivity of ecosystems
• Standing crop vs. Turnover rate

The End For Now

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