Ecosystem Productivity and Soils

Energy Pyramid

GPP vs. NPP• The rate at which an ecosystem’s producers

convert solar energy into chemical energy as biomass is the ecosystem’s gross primary productivity (GPP).

• By what means does this occur? What do you think are some limiting factors?

GPP vs. NPP

• Net primary productivity is the rate at which producers use photosynthesis to store energy minus the rate at which they use some of this stored energy through aerobic respiration.

NPP = GPP – R

• NPP is a measure of how fast producers can provide food needed by consumers in an ecosystem.

Factors Affecting NPP

Global Gross Productivity

Human Use• Humans now use, waste, or destroy about 27% of the earth’s

total potential NPP and 10-55% of the NPP of the planet’s terrestrial ecosystem.

• What might happen to us and to other consumer species if the human population doubles over the next 40-50 years and the per capita consumption of resources such as food, timber, and grassland rises sharply?

Soil• Soil is the base of life on land because it

provides most of the nutrients needed for plant growth.

• Soil is also the earth’s primary filter that cleanses water as it passes through.

How is soil related

to productivity?

Soil Profile

(O Horizon)

Soil Characteristics:

• Texture: percentage of sand, silt, and clay

• Density

• Permeability: water holding capacity

• Porosity

• Ion exchange capacity: ability to absorb and release cations for plant nutrients

• Particle Size