Ecosystem Productivity Principles of Ecology

Primary productivity  The rate at which producers capture & store energy in their tissues  Gross = total  Net = after respiration  The most productive ecosystems in the world  estuaries, swamps, marshes, tropical rain forest

Factors influencing primary productivity  Climate & nutrients  Morphology & size of organism  Rainfall  Temperature  Season  Soil (mineral & nutrient availability)

Net primary production per unit area of the world’s common ecosystems

Trophic Levels  Feeding levels with respect to primary source of energy  Producers & consumers each occupy a different trophic level  Energy is lost at each level

Trophic Levels 1 st Trophic Level Producers Plants 2 nd Trophic Level Primary Consumers Herbivores 3 rd Trophic Level Secondary Consumers Carnivores Decomposer

Biomass Pyramids 1 st Trophic Level Producers Plants 2 nd Trophic Level Herbivores 3 rd Trophic Level Carnivores Decomposer

Biomass Pyramid  The total weight of all living organisms  Biomass at each trophic level  biomass pyramid Biomass pyramid (grams/m 2 ) Producers Herbivores Primary carnivores Top carnivores Detrivores/ decomposers 5

Biomass Pyramids 1 st Trophic Level Producers Plants 2 nd Trophic Level Herbivores 3 rd Trophic Level Carnivores Decomposer

Biomass Pyramids Decomposer At each level some biomass is not passed to next higher level

Biomass decreases at higher trophic levels Not all biomass is consumed from one trophic level to next  Not all that is consumed  Not all that is consumed is digestible  Not all that is digested is turned into mass  Part of mass is converted to energy or heat  Lost mass is available for decomposition

Vegetarianism Shorter food chain/web = less loss of energy Supports idea that vegetarianism is the best way to feed a large population Results in a decrease of human position on food chain Will this solve the world food problem?

 Cellulose  most abundant, naturally occuring organic molecule on earth  Humans can’t digest it  Ruminants can digest it Cattle, sheep, goats Deer, bison, antelope, moose, elk  “Hind-gut fermentors” can digest cellulose Horses, rabbits, some rodents The “Cellulose Solution” Drawing by Mike Hale Cellulose