Applied Ecology ~ Ecosystem Energetics & Energy Flow

Ecosystem

A community of organisms and the abiotic features that interact with the community.

Ecosystem Services

Benefits people receive from ecosystems; grouped into provisioning, regulating, cultural, and supporting services.

Provisioning Services

Resources obtained directly from nature such as food, water, timber, fuel, and medicines.

Regulating Services

Ecosystem processes that moderate natural phenomena, including pollination, water purification, carbon storage, and flood control.

Cultural Services

Non-material benefits from ecosystems such as recreation, religion, art, and cultural identity.

Supporting Services

Underlying ecosystem processes such as photosynthesis, nutrient cycling, soil formation, and the water cycle that sustain life.

Gross Primary Productivity (GPP)

The total amount of carbon fixed by producers in an ecosystem over time.

Net Primary Productivity (NPP)

The actual amount of energy available to consumers after autotroph respiration; NPP = GPP − Respiration.

Secondary Production

The amount of carbon or energy transferred to heterotrophs that consume autotrophs.

Trophic Efficiency

A measure of how efficiently energy is transferred between trophic levels.

Trophic Efficiency Formula

(Pn ÷ Pn−1) × 100.

Energy Pyramid

A diagram showing decreasing energy available at higher trophic levels; typically only 5–20% transfers to the next level.

Biomass Pyramid

A diagram showing the amount of biomass at each trophic level, with higher trophic levels generally having less biomass.

Consumption Efficiency

The percentage of available energy that is actually consumed by an organism.

Assimilation Efficiency

The percentage of consumed energy that is assimilated and used in metabolic processes.

Production Efficiency

The percentage of assimilated energy converted into growth and reproduction.

Detritivore

An organism that consumes dead organic matter.

Decomposer

An organism, primarily bacteria or fungi, that breaks down dead organic matter and absorbs released nutrients.

Food Chain Length (FCL)

The mean number of energy transfers from the base to the top of a food web.

Factors Influencing Food Chain Length

Larger ecosystems, stable ecosystems, and highly productive ecosystems generally have longer food chains.

Biomagnification

The increase in concentration of toxins at higher trophic levels.

What Factors Influence Ecosystem Production?

Climate, nutrient availability, land-use change, species additions or removals, technology use, external inputs, harvesting, resource consumption, and natural drivers influence ecosystem production.

How Does Energy Transfer Between Trophic Levels?

Only a small fraction of energy (about 5–20%) passes to the next trophic level; most is lost through respiration, waste, and detrital pathways.

Bottom-Up Control

The concept that producer abundance and productivity determine the abundance and productivity of organisms at higher trophic levels.

Detrital Food Chain

A pathway of energy flow that begins with dead organic matter consumed by detritivores and decomposers.

Why NPP Matters

NPP indicates ecosystem productivity, affects food availability, helps evaluate ecosystem health, and determines energy flow through food webs.