Ecosystem Ecology

I. Introduction - Ecosystem: an assemblage of organisms, together with their chemical and physical environments

Ecosystem Ecology I. Introduction II. Energy Flow

Ecosystem Ecology I. Introduction II. Energy Flow A. Productivity 1. Gross Primary Productivity Total photosynthetic productivity: CO 2 + H > Glucose + O 2

Ecosystem Ecology I. Introduction II. Energy Flow A. Productivity 1. Gross Primary Productivity Total photosynthetic productivity: CO 2 + H > Glucose + O 2 Metabolism Growth Reproduction

1. Gross Primary Productivity Total photosynthetic productivity: CO 2 + H > Glucose + O 2 Ecosystem Ecology I. Introduction II. Energy Flow A. Productivity

2. Net Primary Productivity: - energy stored in biomass Ecosystem Ecology I. Introduction II. Energy Flow A. Productivity Metabolism Growth Reproduction GPP RESPIRATION NPP

Ecosystem Ecology I. Introduction II. Energy Flow A. Productivity 2. Net Primary Productivity: - energy stored in biomass - measurements

Ecosystem Ecology I. Introduction II. Energy Flow A. Productivity 2. Net Primary Productivity: - energy stored in biomass - measurements - factors affecting NPP

Ecosystem Ecology I. Introduction II. Energy Flow A. Productivity 2. Net Primary Productivity: - energy stored in biomass - measurements - factors affecting NPP - light

Ecosystem Ecology I. Introduction II. Energy Flow A. Productivity 2. Net Primary Productivity: - energy stored in biomass - measurements - factors affecting NPP - light - water

Ecosystem Ecology I. Introduction II. Energy Flow A. Productivity 2. Net Primary Productivity: - energy stored in biomass - measurements - factors affecting NPP - light - water - temp

Ecosystem Ecology I. Introduction II. Energy Flow A. Productivity 2. Net Primary Productivity: - energy stored in biomass - measurements - factors affecting NPP - light - water - temp - nutrients

2. Net Primary Productivity: - factors affecting NPP - Nutrients: Nutrient Use Efficiency = grams of dry mass produced/gram of nutrient absorbed Lower NUE for a nutrient means it is more limiting (need more to produce the same biomass).

2. Net Primary Productivity: - energy stored in biomass - measurements - factors affecting NPP - light - water - temp - nutrients - Global Patterns

2. Net Primary Productivity: - energy stored in biomass - measurements - factors affecting NPP - light - water - temp - nutrients - Global Patterns

Ecosystem Ecology I. Introduction II. Energy Flow A. Productivity 3. Net Secondary Productivity - assimilations efficiencies – A/I seed eaters: 60-80% browsers: 30-40% detritivores: 15%

Ecosystem Ecology I. Introduction II. Energy Flow A. Productivity 3. Net Secondary Productivity - assimilations efficiencies – A/I seed eaters: 60-80% browsers: 30-40% detritivores: 15% herbivores: 60-70% carnivores: 80-90%

Low AE? Must eat more to get energy needed. Horse – ‘hindgut ruminant’ – less efficient, high throughput Cattle – ‘foregut ruminant’ – more efficient, can eat less.

Ecosystem Ecology I. Introduction II. Energy Flow A. Productivity 3. Net Secondary Productivity - affected by nutrient ratios, growth rates, and most limiting variable. May need to eat a lot to get enough of the limiting variable. N:P :: 50:1 N:P :: 15:1 Fast growing; need higher ratio of Phosphorus for DNA synthesis.

Ecosystem Ecology I. Introduction II. Energy Flow A. Productivity 3. Net Secondary Productivity - Net Production Efficiency = P/A

What might this depend on??? NPP NSP

Ecosystem Ecology I. Introduction II. Energy Flow A. Productivity 3. Net Secondary Productivity - net production efficiency = P/A 0.7% Shrews 0.5% Birds 6-10% Most Mammals Up to 75% for sedentary poikilotherms

Ecosystem Ecology I. Introduction II. Energy Flow A.Productivity B.Trophic Pyramids

Ecosystem Ecology I. Introduction II. Energy Flow A.Productivity B.Trophic Pyramids - ecological efficiency: NSP/NPP (5-20%) NPP of Producers (PLANTS) NPP of HERBIVORES Loss due to 2nd Law NPP of Primary Carnivores NPP of Secondary Carnivores

a. trophic "pyramids" NPP of Producers (PLANTS) NPP of HERBIVORES Loss due to 2nd Law NPP of Primary Carnivores NPP of Secondary Carnivores This is why large carnivores are RARE, and why they have large RANGES

Ecosystem Ecology I. Introduction II. Energy Flow A.Productivity B.Trophic Pyramids C.Detrital Foodchains Herbivores Predators

Ecosystem Ecology I. Introduction II. Energy Flow A.Productivity B.Trophic Pyramids C.Detrital Foodchains Herbivores NPP Detritivores Temperate forest: 1.5% - 2.5% Old-field Habitat: 12% Plankton: 60-99%

Ecosystem Ecology I. Introduction II. Energy Flow A.Productivity B.Trophic Pyramids C.Detrital Foodchains D.‘Biomass Accumulation Ratios’ If we know the mean ‘standing crop’ of biomass from year to year, and we know the net productivity, we can calculate how long, on average the biomass persists: BAR (per year) = (biomass/m 2 ) / (np of biomass / m 2 / yr)

Ecosystem Ecology I. Introduction II. Energy Flow A.Productivity B.Trophic Pyramids C.Detrital Foodchains D.‘Biomass Accumulation Ratios’ If we know the mean ‘standing crop’ of biomass from year to year, and we know the net productivity, we can calculate how long, on average the biomass persists: BAR (per year) = (biomass/m 2 ) / (np of biomass / m 2 / yr) Forests: ~ 20 yearsTropical leaf litter: 3 months Phytoplantkon: ~20 daysTemperate leaf litter: 2-20 years

Ecosystem Ecology I. Introduction II. Energy Flow A.Productivity B.Trophic Pyramids C.Detrital Foodchains D.BAR E.Human Concerns

500% increase in 50 years, with population increase of 250%

E. Human Concerns A doubling of meat production per capita

E. Human Concerns 25% of catch by weight discarded

E. Human Concerns

6-10 lbs of feed for 1 lb increase in cattle weight 2-5 lbs of fish meal for 1 lb increase in farmed fish weight

E. Human Concerns Edible kilocalories produced from kilocalories of energy required for cultivation are: 18.1% for chicken, 6.7% for grass-fed beef, 5.7% for farmed salmon 0.9% for shrimp. 123% for potatoes 250% for corn 415% for soy input calories converted to calories able to be utilized by humans So, for every 100 calories of energy we put in to raise chickens, we get 18 calories of energy produced in chicken meat. 100 cal into soy, 415 calories out.

E. Human Concerns Food production, per capita (400 kg per year is healthy minimum)

SO HOW DID WE DO IT?

E. Human Concerns EXTENSIFICATION – MORE AREA

E. Human Concerns EXTENSIFICATION – MORE AREA

E. Human Concerns The best land has already been used; further expansion in marginal areas is costly and requires more supplementation

E. Human Concerns 47% of historical forested land has been cut

E. Human Concerns INTENSIFICATION

E. Human Concerns

The best land has already been used; further expansion in marginal areas is costly and requires more supplementation

E. Human Concerns Global NPP (dry mass) = 224 billion tons. 59% is terrestrial, and of this, humans 35-40% is controlled by humans, either eaten directly or fed to animals we will consume