Ecology: Chapter 21: Ecosystem Energetics



Energy Fixed in the Process of Photosynthesis is Primary Production



Gross primary production

Net primary production



Ocean NPP 2007




Temperature, Water & Nutrients Control Primary Production in Terrestrial Ecosystems


NPP for a variety of terrestrial ecosystems

1000 mm = 40 inches        30oC = 86oF




Relationship between NPP and the length of growing season.

Each dot represents one forest site.




EVT depends on both precipitation and temperature




Primary productivity









Relationship between NPP and nutrient availability

Different forest ecosystems, Blackhawk Island, WI

Abbreviations refer to the dominant tree species in each stand:

  • Hem: hemlock
  • RP: red pine
  • RO: red oak
  • WO: white oak
  • SM: sugar maple
  • WP: white pine




Relationship between aboveground NPP and nitrogen availability






Temperature, Light & Nutrients Control Primary Production in Aquatic Ecosystems












Primary production in the world's oceans.





Energy Allocation and Plant Life-Form Influence Primary Production


Relationship between standing biomass and NPP.





Primary Production Varies With Time





Changes in proportions of biomass for white oak trees as trees age.











Ecosystems Have Two major Food Chains

Orange Arrows = energy flow associated with ingestion

Brown Arrows = dead organic matter/waste products

R = respiration