Chapter 18 - Primary Production and Energy Flow

What is Primary Production?

Autotrophic energy fixation (Energy gathered by plants from the sun)

There are two ways to quantify Primary Production, what are they?

GPP (Gross Primary Production) and NPP (Net Primary Production)

What is GPP?

Total energy captured

What is NPP?

GPP - Autotrophic Respiration

In Terrestrial Primary Production (Plants on Land), what is GPP responsive to? (Three things)

Temperature, Moisture, and Nutrients

What is Annual Actual Evapotranspiration (AET) ?

Amount of water that evaporates and transpires off a landscape every year

Cold and Dry environments tend to have a relatively ___ AET? What does this mean for Hot and Wet environments?

Low AET, this means that Hot and Wet environments will have a high AET

Tundra and Deserts are environments with relatively low AET, what resource are each limited to?

Tundra is energy limited while Deserts are water limited

What is Liebig's law of Minimum?

Growth is limited by the scarcest of resources

According to Liebig's Law of Minimum, what would NPP be greatly affected by?

Soil Fertility

When looking at Aquatic Primary Production (Plants in the Water) what are they usually limited by?

Nutrients, especially Phosphorus.

What happened when Phosphorus was added to Aquatic Environments that were limited to it?

Growth of Algae Blooms

Which Aquatic Environment zones yielded the highest amount of Productivity? Why?

Coastal Zones and Upwelling Areas due to runoff and cycling of nutrients

According to the Cedar Creek Experiment plots that had the highest ______ yielded the most NPP, why is this the case?

Plots that had the highest # of species, this is because Biodiversity increases NPP and can be as strong as fertilization.

What is the general flow of trophic levels in an ecosystem?

Primary Producers > Herbivores > Predators > Apex Predators

How much energy is loss per trophic level?

We lose ~10% energy every time we go up a trophic level from herbivores, however, we lose ~99% of energy from Primary Producers to Herbivores

What is Bottom-Up control?

Productivity is determined by the presence of resources (Ex. Rainfall increases NPP since it supports moderate grazing therefore increasing NPP)

What is Top-Down control?

Consumers are what regulates Productivity (Bass eats small fish which increases zooplankton which ultimately decreases algae and decreasing NPP)

Addition of Fertilizer to Aquatic environments increased production by how much?

20-300% increase in NPP

What are the different ways that Energy is loss through trophic levels? (There are 5)

Excretion,

Egestion,

Respiration,

Assimilation,

Production

Where does most of Human Agricultural production goes to what? What does this say about efficiency?

Animal Feed, it is extremely inefficient

When considering the strength of Top-Down or Bottom-Up controls, which had the strongest effect on production?

Top-Down

Why do grazers increase primary production?

They can lower respiration, self-shading, and improve water balance.

Which intensity of grazing yielded the highest primary production?

Moderate grazing (Intermediate Disturbance Hypothesis)