Food Chains and Biomass Pyramids on Rangelands

1. Food Chains and Biomass Pyramids on Rangelands J. Peterson USDA-ARS

2. 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

3. Trophic Levels Heat Heat Decomposer 1stTrophic Level Producers Plants 2ndTrophic Level Primary Consumers Herbivores 3rdTrophic Level Secondary Consumers Carnivores

4. Biomass Pyramids 3rdTrophic Level Carnivores Heat Heat 2ndTrophic Level Herbivores 1stTrophic Level Producers Plants Decomposer

5. Biomass Pyramid • The total weight of all living organisms • Biomass at each trophic level  biomass pyramid 1.5 Biomass pyramid (grams/m2) Top carnivores 11 Primary carnivores 37 Herbivores 809 Detrivores/ decomposers Producers 5

6. Biomass Pyramids 3rdTrophic Level Carnivores Heat Heat 2ndTrophic Level Herbivores 1stTrophic Level Producers Plants Decomposer

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

8. 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

9. Vegetarian Solution? Shorter food chain/web = less loss of energy • Vegetarianism results in a decrease of human position on food chain. • Is vegetarianism is the best way to feed a large population? Will this solve the worldfood problem?

10. Two Good Reasons 1) Cellulose  most abundant, naturally occurring organic molecule on earth • Humans can’t digest cellulose, • Ruminants & Hind-gut fermtorscan. • We need cows, sheep, goats, horses, llamas, alpacas, etc. to digest cellulose for us. 2) Only about 10% of the earth land surface can be farmed. • The rest is too rocky, too cold, or too dry. • We need animals to harvest these land for us. Drawing by Mike Hale